including its size, quality of contrast and the accuracy of the electron gun65, 66 ...... However, in addition to its us
STYLE GUIDE FOR THE DESIGN OF INTERACTIVE TELEVISION SERVICES FOR ELDERLY VIEWERS
Dr Alex Carmichael ITC Research Fellow December 1999
Contents Expectations and acceptance of new
Foreword Preface
vi
technology ................................................. 34
Introduction
1
Limitations of questionnaire data............ 37
Part Two:
Part One: Relevant characterisitics of elderly viewers
3
Relating human factors to interface and
4
Chapter 5:
Chapter 1: age related changes in ability Chapter 2: perception 8 Vision............................................................8 Changes in the eye ...................................8 Changes in visual processing .................10 Hearing ......................................................11 Changes in the ear..................................11 Audiometric aspects................................13 Hearing for speech..................................14 Touch etc ...................................................17 Chapter 3: cognition ‘Crystallised’ and ‘Fluid’ cognitive
interaction elements
39
static elements 40 Visual.......................................................... 40 Text ......................................................... 41 Screen layout.......................................... 45 Icons and logos....................................... 48 Highlights and pointers ........................... 50 Aural ........................................................... 62 Audio prompts and ‘earcons’ .................. 62 Speech and ‘noise’ ................................. 64 Chapter 6: dynamic elements 66 Searching and navigation ........................ 66 Differences of ‘network’ connection
19
abilities .......................................................20 The ‘general slowing’ hypothesis............21 Attention.....................................................22 Working memory .......................................25 Recall and recognition..............................25 Bi-modal augmentation/interference.......27 Interrelatedness of perception and cognition ....................................................28
structure .................................................. 70 Transactions.............................................. 72 Screen transitions..................................... 76 Prompts and reminders .......................... 76 Guiding attention..................................... 77 Consistency............................................... 79 Chapter 7: input elements 81 ‘Traditional’ remote control devices ....... 81 ‘Novel’ approaches to user input ............ 86
Chapter 4:
‘Data glove’ input .................................... 87
other individual differences 30 Motor function ...........................................30
Voice input .............................................. 88
Cohort/cultural differences ......................31
‘Specialist’ vs ‘Universal’ input devices ...................................................... 90
Chapter 8: guidelines REFERENCES
94 100
Example Boxes A: Selected items from the ‘Mill Hill’ and ‘AH4’ tests. ......................................................21 B: Samples of commonly used ambiguous figures .........................................................23 C: Anecdotal evidence that ‘one wrong move will break it’. .............................................32 D: Even apparently non-depressed elderly volunteers are ready to blame themselves rather than the system, even though most of the errors were due to inadequate on-line instructions...................... ............................................................................34
E: The effective size of a character varies with viewing distance. ....................................42 F: Examples of some of the font characteristics which can affect legibility........................43 G: Various keypad arrays commonly used on ‘standard’ remote control handsets..........51 H: An illustrative example of an interaction task which may have benefited from more considered use of ‘highlighting’, ‘lowlighting’ and constraint of operations. ...................53 I: Booking cinema tickets: the importance of easy error correction ..................................56 J: Alternative on-screen pointer options. .......................................................................58 K: Various elements can be altered to make it clear when a pointer is on a target item. .........................................................................................................60 L: The ‘highlighting’ of a target item could include symbols denoting different ‘functions’............................................................ ..............................61 M: Searching a simulated interactive television service for films and TV programmes ......67 N: Simplified illustrations of different types of ‘network’ ..................................................71
Foreword Elderly people represent the largest proportion of the television viewing public and at the same time represent a proportion of society which is least familiar with the conventions and practices of today’s information presentation. For many of us, interpreting: menus, matrices, hypertext links, soft keys, hierarchies and icons is an everyday task, but it can present special challenges for elderly people, challenges which may soon become unavoidable. Electronic programme guides, interactive television, home servers and home networks will all require some knowledge of information display and retrieval processes, not to mention a level of physical ability to manipulate the input device and visual acuity to read the onscreen text. Difficulties for elderly people often arise, not so much because they do not know how to use the systems, but because the designers of individual services have not been thoughtful enough to consider the cognitive, sensory and physical limitations that so many potential users will suffer from. Navigating deep hierarchical structures, for example, can be impossible for people with short-term memory problems; breaking conventions of display style to achieve a ‘creative’ corporate look can simply lead to confusion; inappropriate choices of colour can render text illegible when seen through an elderly eye lens; and pointing a cursor at an inadequately small soft key can be impossible with muscular tremor. In the fast-changing and daunting world of broadcast media technology, the ITC is working to ensure that the interests of elderly and disabled viewers are considered in the design of new broadcast systems and services, and it has a distinguished history of initiatives in this area. This report maintains this tradition through its careful assessment of the potential difficulties encountered by elderly subjects in their attempts to use a range of services made available through an advanced interactive television system. It is presented in the form of a guide to help designers of information systems using television displays, to communicate more effectively with elderly viewers. The ITC would like to express its thanks to the team at Manchester University’s Age & Cognitive Performance Research Centre who carried out this study for us: Prof. Pat Rabbitt, Dr Alex Carmichael and Ms Linda Hazel. We are also grateful to On-Line Media of Cambridge for access to their interactive television equipment and to the many elderly citizens of Manchester who patiently assisted us with the experiments. Dr Nicolas Lodge Head of Standards & Technology
Preface The aim of this document is to offer guidance to those involved in designing interactive television services and are concerned that they can be easily accessed by older people. It is hoped that the information presented here will be understandable to those without any particular background in psychology, human factors and the various other disciplines which have informed the content of this Style Guide. Thus, the use of jargon has been kept to a minimum and any such terminology which is used is defined as clearly as possible in ‘lay’ terms. Also, specific attention will be paid to contradicting various ‘popular misconceptions’ that may relate to some of the areas covered, which have become apparent to the author while working in this field. Reference to specific studies from which information has been drawn will be kept as brief as seems appropriate. Therefore, details of methodologies, measures, and theoretical backgrounds used, will only be described where necessary for understanding of the (usually fairly general) points being made. Thus, many such details will be omitted, however, full references are given to all work mentioned so that, should it be required, the interested reader may follow up on any particular topic in much greater detail. To minimise disruption to readers in general, such references will be indicated in the main text by the use of numbered citations. Given the rapid changes in the development of technology relevant to the issues covered in this Style Guide and as research into the relevant aspects of older people also seems to be ‘booming’, it is anticipated that the Style Guide will be regularly updated with new editions as appropriate. Along similar lines it is hoped that at some point in the near future it will also be developed into a ‘hyper document’ of some kind and will thus be more readily updated and hopefully more accessible to those who want to make use of it.
Introduction
As described in the Preface, this Style Guide is an attempt to set up an accessible framework for undertaking the human/system aspects of the design of multimedia interactive systems for the elderly. The chapters in Part One describe the changes observed in older populations, in sensory/perceptual systems, cognitive abilities and other behavioural aspects found to be relevant to the use of interactive systems. The chapters in Part Two build on this by specifically relating these ‘human factors’ to various aspects of interface design. Throughout the Style Guide the relatively general discussions in the main text will be further illustrated with more specific ‘case study’ examples. These examples will be presented separately from the main text in shaded boxes (see Example X: case study, below) but will generally be placed as closely as possible to the text that they aim to expand upon. It is hoped that this approach will provide a more meaningful insight into the principles of good practice than would a check-list of ‘dos and don’ts’. It is also hoped that such insight as can be provided will be much more adaptable in a context of extremely rapid technical development (as is likely to characterise television services in the near future) than could any prescriptive check-list.
Example X: Case study.
The aim of these example case studies is to ‘put some meat on the bones’ of the general discussions presented in the main body of text. They are not designed to ‘prove’ any of the theoretical constructs described, rather to illustrate a particular instance of a more general principle which the author has attempted to describe in the main text. Thus, there will be a tendency for these examples to be described and discussed in rather less ‘formal’ terms than will generally be found in the main text.
It is hoped that combining general theoretical principles with specific (but illustrative) examples in this way, offers greater potential for the resulting ‘guidelines’ to be usefully adapted and applied by designers of new and currently unforeseen elements of interactive services. Another benefit will also be obtained by drawing together the findings of a range of research spanning from the purely theoretical to the directly applied and using it to guide further investigations into applied settings constrained by careful experimental control. That is, by addressing such ‘real world’ issues (albeit 1
with the principal aim of providing an ‘immediate’ answer to a practical problem) the true complexity of everyday tasks can become apparent. The degree of this complexity (eg the wide range of influential factors involved etc) can often expose existing theory as inadequate but can equally offer suggestions for the nature of that inadequacy. Also, if, as here, the applied research is based on the theoretical literature, its findings can be validly fed back so as to indicate fruitful new lines of either theoretical or applied research. This point was well summarised some years ago by another psychologist who disagreed with the view that applied research lacks academic value1: By looking at difficulties that arise in real life, one is forced to think more rigorously and to consider variables which it is easy to forget while in the fastness of theory. A similar view has been expressed from the field of gerontology2. Wherein, the connection between theoretical and applied issues described above is seen as ‘... a crucial step of translation required to bridge the gap between the conclusions of experimental investigators and solutions to practical difficulties.’ Recent booms in television related information technology and the size of the elderly population have combined to produce a new wealth of questions about the ability of older people to cope with such technology and services and also the ability of interactive service technology to help older people. Because such a large amount of these, and similar questions, have recently emerged in a wide range of technological domains, a large number of researchers have started addressing them, both individually and in collaboration (within and across ‘traditional’ disciplines). This ‘new’ approach has been dubbed Gerontechnology3 and is generally characterised as ‘the study of technology and ageing with the aim of improving the functioning of the elderly in daily life.’ The scope of this approach is much broader than just ageing and cognitive psychology. Regardless of the specific disciplines involved, the originators of Gerontechnology would likely agree with the argument presented above and strongly promote the idea of attacking practical problems with a theoretical armoury. In this way the solutions attained do not just have practical but also theoretical importance. Also, the accumulation of those solutions will provide better preparation for further changes in all aspects of information technology (or, indeed, in the elderly population). The final chapter of this document will summarise the main points made previously in as concise a way as possible. However, these guidelines should not be used as a check-list in isolation but are rather presented as simplified reminders of some of the more complex points made in earlier chapters.
2
Part One Relevant characteristics of elderly viewers
Chapter
1
age related changes in ability
In order to optimise the design of multimedia interactive systems for older users there are three quite different frameworks, used to describe the process of human ageing, which are equally important to bear in mind. First, ageing can be viewed as a process, independent of any pathologies or disabilities, causing characteristic changes in the efficiency of the sense organs, the entire central nervous system (CNS) in general, the respiratory and cardiovascular systems, the skeleto-muscular system and, indeed, all systems which determine a person’s total physiological and cognitive competence. Within this framework of description the problem is to assess the scope, relative severity and rates of decline of these various changes in order to predict the problems that elderly users may have with the communications systems that we wish to design. A second view of ageing is more focused on the remorseless accumulation of more or less severe pathologies. The impact of each particular pathology may be slight, and may progress very slowly but, independently and interactively, they will tend to circumscribe everyday competence. An extreme version of this view is that during ageing there is also a very marked increase in the incidence of serious handicaps and disabilities. From this standpoint, good design for the elderly tends to be regarded as an extension of design for the handicapped with the addition that with their multiple minor disabilities, older people may also suffer from changes in efficiency brought about by ‘normal’ ageing. It is crucial to emphasise a third, and equally valid view of ageing as the culmination of a lifetime’s acquisition of knowledge, of sophisticated information handling procedures and of expert skills which young adults have not had time to learn. The negative changes associated with biological ageing may erode some of these acquired skills but others may be almost indefinitely retained at a very high level of competence4. Possession of these skills means that older people can often compensate for physiological limitations in ways which may not be possible for the younger people (whether disabled or not).
4
For example, a study examining differences between older (more experienced) and younger (less experienced) typists demonstrated that; ‘Older typists were slower in tapping rate and in choice reaction time (both considered basic components of typing ability) but were not slower in speed of typing, apparently because they were more sensitive to characters farther in advance of the currently typed character than young typists.’5 (Parentheses added.) Further, while the marked growth in the numbers of elderly people in affluent societies has been widely publicised, it is not sufficiently recognised that this growth also implies marked increases in the absolute numbers and in the proportions of elderly people who remain healthy and active into their late 70s and early 80s, and who experience only modest reductions in their abilities to cope with their daily lives. For designers of products and services this also means that condescending or patronising design solutions are certain to be recognised and rejected by individuals whose expectations may be at least as sophisticated as those of the people who design for them. In general it is important to note that even healthy normal old age is accompanied by an accumulation of mild but progressive losses of efficiency in all sense organs. These have been comprehensively documented6. For example, in vision these changes include marked reduction in the amount of light that actually reaches the retina with a corresponding loss of contrast sensitivity; this is accompanied by loss of retinal receptor cells which causes reduction of visual acuity, restriction of the visual field, loss of efficiency of dark adapted vision, and reduction of colour sensitivity. Changes in hearing include marked increases in detection thresholds for pure tones, especially for higher frequencies, accompanying this are a relatively greater increase in thresholds for speech perception. It has been indicated that the latter is due less to hearing ability per se, than to ‘time related processing abilities’ which become less efficient in old age and so are increasingly challenged by the rapid flow of dense and complex information which forms the speech wave7. A further related change is a selective loss of the ability to distinguish speech sounds against any form of noisy background. There are also changes in vestibular function leading to some loss of sensitivity to changes in bodily orientation, changes in tactile sensitivity, in sensitivity of the skin to changes in temperature, and losses in efficiency of the senses of smell and taste. For designers the point to bear in mind here is that the combined impacts of mild losses cannot be understood in terms of a simple check-list of their individual effects. Sensory losses in separate modalities, such as decrements in hearing and vision, or in taste and smell, often act in combination to produce greater restrictions in performance than would be assumed from the simple sum of their individual effects. For example, when we follow a television programme, sight and sound cues reinforce each other in complex ways. A spoken sentence is often only intelligible if we can also see what is happening, and an action or change in facial expression only makes
5
sense if we also hear what has just been said. We live in a rapidly changing multi-modal environment, and we can only effectively keep up with it by simultaneously integrating sensory information from many different sources. Another characteristic of sensory changes in old age is that severe loss in one sensory modality is usually accompanied by slight losses in others (as distinct from the popular myth that loss of one sense is accompanied by a ‘compensating’ enhancement of another). For example, elderly blind or partially-sighted people are, typically, also slightly deaf. They also may have poorer memories and so become less efficient at remembering the spatial layouts of things in their environment. They also have usually lost some degree of tactile sensitivity which means they will tend to find Braille more difficult to read and will similarly have more difficulty with various aspects of remote control use. A third point is that many people reach the latter stages of their lives having experienced only mild sensory losses which are easily, and satisfactorily, remedied by prostheses. It is also the case that the incidence and prevalence of severe sensory, and other disabilities will markedly increase with the age of the population for which interactive systems are to be designed. A good example of this is that the vast majority of people registered in the UK as either being blind or deaf are aged over 65 years. Even more important than the sharp increase in incidence of single disabilities is the fact that the joint incidence of severe multiple disabilities also markedly increases in old age. This occurs because particular conditions, such as peripheral neuritis caused by diabetes, will produce marked loss in more than one sensory modality, such as vision, hearing and touch. Multiple disabilities can of course occur at any age. In old age multiple sensory losses not only become more common but also take place against a background of changes in the efficiency of the CNS that gradually reduce effective information processing speed, learning rate and short-term memory efficiency. In effect this amounts to a loss of back-up computing power that would otherwise have the potential to compensate for degradations of sensory input. It is not sufficiently recognised that, at any age, even only mild degradation of sensory input can make additional demands on information processing capacity. As will be described in the following chapters, loss of information processing speed and degradation of sensory input can interact to place a double, and sometimes unsustainable, demand on the ageing cognitive system. Another critical point to understand about age-related declines in ability, is that such declines relate to the average ability of a particular elderly population and not to the ability of that entire elderly population. That is, to claim that elderly people require a larger typeface than younger ones is true, up to a point. What this claim misses is that some elderly people will cope with small typefaces just as well as younger ones, while at the other extreme there are some elderly
6
people who require typefaces even larger than most of their contemporaries. In other words, all age-related declines in ability are associated with wider variability between the ‘best’ and the ‘worst’. Adding this complication to the interactive effects of disparate declines described above, strongly suggests that while the information in this document should provide invaluable guidance for the initial design of an interactive system, it cannot replace the need for rigorous user testing with appropriate populations (although it should limit the number of ‘surprises’ revealed by such tests). The following two chapters cover ‘perception’ and ‘cognition’, however, this distinction should not be construed as implying mutual exclusivity between these areas. That is to say, it would be misleading to believe that there is some clear dividing line between perception and cognition. Further, the chapter covering perception will also cover aspects of sensory function as, for present purposes, they are so closely interrelated that it would be of little benefit to labour the theoretical distinctions. Although it could be argued that perception and cognition are equally interrelated, there is also good reason (again, for present purposes) to present them as separate topics. In other words, sensory and perceptual processes can be considered as the mechanisms responsible for conveying ‘input’, whereas cognitive processes are the mechanisms which act upon that input. While there is a certain utility in this loose ‘computer’ metaphor it is also an over-simplification, however, any ‘exceptions to the rule’ will be indicated and described as appropriate. For example, there are situations where a person’s expectations (a cognitive process) can influence the sensory/perceptual input that is (or is not) attended to and also the way that input may be acted upon. The aim of these chapters, therefore, will be to present enough detail about the complex changes experienced by older adults so that they can be adequately met by subsequent system design, whilst remaining in close enough touch with ‘real world’ abilities and their implications, that prior knowledge of psychological science is not necessary for understanding the issues involved.
7
Chapter
2
perception
It is important to note at the outset that human perception does not simply record the outside world. There is a wealth of good evidence to suggest that sensory information is often significantly altered before it reaches consciousness8. Although there is continuing debate about the precise nature of these alterations (and other issues) in theoretical circles, the main point here is that knowledge of what is available to the sensory systems does not necessarily equate to the product of those systems. This idea is stated more simply (and in the context of vision) as ‘What one sees will be what one expects to see, given one’s lifetime of perceptual experience’9. This is particularly so for elderly people who will have relatively more ‘perceptual experience’ to influence the interpretation of relatively less reliable sensory information. The following sections will attempt to describe the reasons why such information is less reliable in older people.
Vision Changes in the eye
The ageing eye undergoes various changes which are known to affect the quality of vision, and there is an extensive corpus of literature from a variety of scientific disciplines. The following findings have been mainly drawn from a recent review with similar aims to the present document10. However, reference will be made to other relevant sources as appropriate. The following discussion will describe the relevant physical changes which occur in the ageing eye (see Figure 1), the next section will then address the related issue of visual processing. The pupil controls the amount of light entering the eye and it has been found that the absolute diameter of the pupil gets smaller with age. The extent of this relative reduction in diameter is even more prominent at low light levels. This means that less light enters elderly eyes than younger ones, particularly when there is less light available. This relative paucity of light is compounded by the elderly lens becoming less transparent (cataracts) and thus absorbing relatively more of the light
8
that is passed by the pupil. This increased opacity of the lens can be relatively generalised or somewhat ‘patchy’. Although cataracts can often be treated with surgery, it is estimated that around half of those over the age of 65 have some cataract development.
Figure 1: The human eye showing the various structures referred to in the text.
The lens also becomes more rigid with age and is thus less able to adjust (or ‘accommodate’) to requirements of near vision (again, a deficit exacerbated by low light levels). These, and other factors also produce a greater scattering of light within the eye, which means that the weaker ‘signal’ reaching the retina is accompanied by relatively more ‘noise’. Based on these findings, it has been claimed that, in general, elderly people require an increase in illuminance three times that of younger people. In competition with this requirement for higher light levels is the finding that elderly people are more susceptible to the effects of glare. Such that, regardless of the above problems, older people have significantly lower thresholds for ‘discomfort’ glare than younger people. It has also been found that susceptibility to ‘disability’ glare is directly proportional to a person’s minimum illuminance threshold, which, as described above, tend to be higher in older people. There are claims that elderly people experience reductions in colour discrimination. However, findings in this area are more equivocal than those described above. Although it has been shown that cataracts in the ageing lens produce yellowing, effectively making the lens a colour filter. As with many of the declines outlined above, the influence of this filter becomes more pronounced at low light levels. Such light as does pass through the ageing eye is then received by the retina. However, the vast majority of older people will suffer some degree of age-related macular degeneration. The macula (also known as the fovea) is the part of the retina with a relatively greater density of receptor cells and receives light from the centre of the visual field, allowing detailed activities such as reading which requires high levels of precision in detecting changes in contrast (ie ‘edges’). Although the precise cause (other than ‘normal’ ageing) is not known, the result of macular degeneration can range from a decline in acuity to a complete lack of vision in the centre of the visual field. This effect of ‘normal’ ageing can be compounded by a variety of other
9
damages to the retina due to diabetes, the incidence of which also increases markedly with advanced age. The problems caused by diabetic retinopathy mainly stem from damage to the fine blood vessels in the retina (and the resulting scar tissue). This can damage even more of the receptor cells in the macular and throughout the retina in general. The most common outcome of this is some degree of blurred or patchy vision and/or distortion of the visual field. The information received by the retina passes down the optic nerve to be processed in the brain. However, this pathway can be damaged by glaucoma, which although particularly uncommon in younger adults, effects around 5 per cent of people over the age of 65. In general, glaucoma (which can have various causes, one of which is diabetes) results in elevated pressure within the eye. This can damage the optic nerve fibres at the point where they leave the eye, known as the ‘blind spot’ or ‘optic disc’. The result of this can be a ‘halo’ of visual loss around the centre of the visual field, if untreated the loss can spread to cause ‘tunnel vision’ or in extreme cases total blindness. Also, whereas the visual problems described above are generally apparent to the sufferer, the ‘neural blindness’ caused by glaucoma may often go unnoticed, particularly if that person is also subject to other visual disturbances. Certain changes in the motor function of the eye may also be relevant here. Although no particular problems have been found in the ability to maintain a steady gaze (fixation) in older people, some dynamic aspects of motor control do seem to be impaired in later life. In many ‘everyday’ visual activities (eg reading) eye movement is characterised by fixations and saccades (ie very rapid movement between fixation points, during which information intake is relatively reduced). It has been found that in elderly people, saccades (particularly relatively large ones) tend to take longer and are less precise, to the extent that in some situations an initial saccade can over- or under-shoot, requiring further smaller ‘adjustment’ saccades to reach the target. It has also been found that older people have relative difficulty in ‘smooth pursuit’ tasks (ie maintaining fixation on a moving ‘object’). Changes in visual processing
It is generally accepted that combinations of the factors described in the previous section form the basis for the observed reduction in standard measures of visual acuity in older people. Thus, it is perhaps not surprising that an older person’s level of acuity is even further reduced in low light conditions. It is also worth noting that there is no reliable relationship between a person’s level of acuity in ‘good’ light and that same person’s acuity in ‘poor’ light. In addition, an older person’s level of acuity in any of these contexts is further reduced if the target item is moving. The extent of the visual field also declines with increasing age. A basic foundation for this finding is the small but relatively reliable decline in measures of clinical vision perimetry. However, various studies have demonstrated that the difficulties older people experience with their peripheral vision in complex, ‘real world’ scenes tend to be more pronounced than would be predicted by clinical measures of identifying discrete targets against ‘blank’ backgrounds. A possible clue to these extra difficulties comes from general theoretical research into visual cognition. Although there remains some dispute over the theoretical details, there is a variety of evidence which indicates that the greater the requirement for attention at the centre of the visual field (eg identifying a degraded, rather than a clear letter) the more likely
10
items at the periphery will be missed9. Findings such as these have led to the development of the concept of a ‘functional’ or ‘useful’ field of view. Experiments based on this framework and involving older volunteers indicate that the useful field of view does decline with age. It has also been suggested that measures of the useful field of view give a better estimate of the problems older people report about their ‘real world’ peripheral vision, than do clinical measures11. A variety of research suggests that older people tend to have problems with depth perception 12. It should be noted that our sense of depth in a visual scene is based on two different forms of information (or ‘cues’). First, there are monocular cues, such as: object overlap, the laws of perspective, diminishing texture gradients, and the effects of atmospheric impurity. Of these, only those requiring a degree of visual acuity (eg changes in surface textures) are generally affected in elderly people. Second, there are binocular cues, which are based on the subtle disparities between the views of each eye. Although little research has directly addressed these issues, it seems reasonable to assume that the changes described above which result in less light entering the eye, more scattering of light within the eye, and limitations in motor control are also related to observed declines in depth perception in older people. Similarly, depth perception at close range is likely to be affected by the limitations in lens accommodation and possibly compounded by related deficiencies in binocular convergence (ie the ability to go [accurately] ‘cross-eyed’ when viewing detail close up). While depth perception is unlikely to be particularly relevant to the majority of current displays, these factors may well become crucial with the development of emerging technologies such as; pseudo-3D displays, ‘virtual reality’ interfaces, and stereoscopic televisions.
Hearing Changes in the ear
It has been documented that the pinna (ie the external structure of the ear, also known as the auricle) tends to become larger and stiffer with age (see Figure 2). Although there is no apparent evidence to suggest that this is linked to hearing ability per se, these changes do seem to have a negative impact on the ability to localise the source of sounds13. It has been found that the supporting walls of the external ear canal show signs of atrophy and become weaker in later life. An important aspect of this change is that certain ‘on-the-ear’ (as distinct from ‘in-’ or ‘round-the-ear’) headphones can effectively collapse the walls, giving an effect similar to putting your fingers in your ears. A more common impact of these changes stems from the finding that the ear canals of young people will resonate to (and thus amplify) pressure waves within the frequency bandwidth of human hearing. On this basis it has been suggested that the age-related deterioration of this structure reduce (or even remove) the effects of this ‘pre-amplification’ mechanism. Thus, elderly people tend to have a relatively lower ‘volume’ of sound reaching their tympanic membrane (eardrum).
11
Pinna
Figure 2: The human ear showing the various structures referred to in the text.
Also, the transmission of sound down the ear canal can be affected by excessive accumulations of cerumen (ear wax). This condition is found to be more prevalent in older people, although it is not known whether this is mainly due to changes in the mechanisms responsible for producing the wax or whether earlier stages of accumulation fail to be noticed (and thus, brought to a clinician’s attention) because the effects of other forms of age-related hearing loss effectively ‘mask’ it. That is to say, a subjectively detected change in hearing is the main factor behind people with this condition seeking the advice of their doctor/audiologist, for young people this will generally be well before the accumulation can be characterised as ‘excessive’. Another major effect on hearing ability in later life is the tendency of the tympanic membrane to become less flexible, making it less responsive to incoming sound. The causes of this stiffening of the eardrum are varied but fall into three main categories. That is, these changes are partly due to the effects of ‘normal’ ageing, partly to the effects of ‘damage’ (ie older people have more ‘opportunity’ to suffer noise or disease related damage, than younger ones) they are also partly due to a ‘cohort’ difference (ie today’s older generation are more likely to have worked in environments now known to be detrimental to hearing). A less flexible eardrum further reduces the ‘volume’ of sound reaching the middle ear. The middle ear is filled with fluid and sound is transmitted through this chamber via the bones of the ossicular chain. It is known that blockage of the eustacian tube can cause the fluid pressure to rise which restricts the movement of the ossicular chain, effectively reducing the power of the signal being transmitted. It has been shown that elderly people are more likely to suffer blockages to the eustacian tube (anyone who has had a bad ‘head cold’ will have likely experienced a form of this sort of hearing loss). There is also evidence indicating that older people are more likely to show signs of arthritis in the joints between the malleus (hammer) and the incus (anvil) and between the incus and the stapes (stirrup). However, at present there is no direct evidence to indicate that this has a quantifiable effect on hearing ability.
12
The vibrations of the ossicular chain are passed from the stapes to the oval window (another flexible membrane) at the ‘entrance’ to the cochlea and (due to the laws of dynamics for incompressible fluids) are transmitted throughout the internal structure of the cochlea to the round window (a further flexible membrane), the vibration of which allows the ‘old’ vibrations to be dissipated. Like the eardrum, the membranes in both of these ‘windows’ become less flexible with advanced age. This means a further ‘dampening’ of incoming sound and an increase in ambient ‘noise’, due to the less than perfect dissipation of ‘old’ vibrations. There are a wide variety of changes within the cochlea and the inner ear. A full description of these is beyond the scope of this document, however, the effects of these changes are generally captured by the term presbyacusis (alternatively presbycusis). Basically, by definition presbyacusis is ‘age-related hearing loss’, however, efforts have been made to examine the different causal factors involved in this condition. Four basic ‘types’ of presbyacusis have been indicated. First, there is mechanical presbyacusis, which is basically covered by the preceding paragraphs (and similar ‘mechanical’ changes within the cochlea). Then there is sensory presbyacusis which is due to changes in the receptor (‘hair’) cells throughout the cochlea. There is metabolic presbyacusis which involves changes in the properties of the fluids in the cochlea. Finally, there is neural presbyacusis which involves the loss of neurons in the auditory nerve pathways. Audiometric aspects
Audiometry measures the quietest level at which a person can detect pure tones. Most commonly, these measures are taken against a ‘no noise’ background, however, more complex measures can be taken in conjunction with levels of ‘masking’ white noise, and measures of ‘bone conduction’ (ie sound reaching the inner ear via the skull, rather than the ear canal). Minimum threshold levels are taken for a range of frequencies across the audible spectrum. The standard frequencies which tend to be used are; 125Hz, 250Hz, 500Hz, 1kHz, 2kHz, 4kHz, 6kHz, 8kHz and 12kHz. These measures give a useful indication of a person’s hearing ability for sounds in general but, as will be described below, they demonstrate only a loose relationship with hearing ability for human speech, this is particularly so for older people. Assessing audiometric data gathered from elderly populations has certain inherent problems. One major aspect of these difficulties relates to the use of ‘screened’ and ‘unscreened’ samples of volunteers. Simply stated, a screened sample means that it does not include data from people known to have hearing loss which is caused by factors other than ‘normal’ ageing (eg identifiable ‘noise’ damage). In general terms, this means that data gathered from unscreened samples of the population would be the most likely to reflect the hearing ability of the elderly population in the ‘real world’. However (and mainly due to research funding priorities), the most reliable surveys of audiometric data are based on screened samples. On this basis the following overview of this data should be considered as somewhat conservative. In general, hearing for pure tones up to 1kHz is only moderately affected by advanced age. Minimum threshold levels tend to be raised by about 5 to10dB by the age of 50, and by about 15 to 20dB by the age of 70. It is also generally found that hearing for
13
all these lower frequencies declines at about the same rate within a particular individual (ie these changes seem to be frequency independent). A rather different pattern emerges for hearing thresholds for tones above 1kHz. The first aspect of this difference is that hearing for tones between 2 to 6kHz (but not for 8kHz and higher) is relatively better than for lower tones, up to about the age of 40 years. From this age on, hearing for tones of 2 to 6kHz deteriorates relatively rapidly, such that by the age of around 50 or 60 it is poorer than for lower frequency tones. The second important aspect is that hearing for all the higher frequencies, in addition to the relatively rapid deterioration mentioned above, tends to deteriorate in a frequency dependent manner. That is, the extent of hearing loss tends to be greater for higher frequencies. For example, average thresholds for 2kHz are about 5 to 10dB around the age of 30, this will have elevated to about 20 to 25dB by the age of 50 and to 30 to 40dB by 70. By contrast, thresholds for 8kHz are around 15 to 20dB at 30, rising to 30 to 40dB by 50 and to 55 to 65dB by age 70. Beyond simple detection thresholds, another basic audiological function has also been shown to deteriorate with age. That is the ability to distinguish between pure tones of differing pitch (played well above the individual’s relevant threshold levels). Similar to the threshold data above, these changes have been found to be both age and frequency dependent. That is to say, the difference between two pitches that is necessary to reliably distinguish them begins to get relatively bigger from as early as age 30. From this age onwards the required difference in pitches becomes progressively bigger and disproportionately so the further above 1kHz the frequencies are. This suggests that pure tones which can be heard clearly (ie above threshold) will tend to be ‘blurred’ around that central frequency. Before turning to the factors influencing hearing for speech, there is another aspect of auditory processing that is worthy of note at this point. It is known that in general ‘simple reaction time’ (ie the highest speed at which a response can be given to some external stimulus) gets longer with increased age. This is taken to reflect the general deterioration of the elderly CNS. Studies comparing simple reaction times to different modes of stimuli, indicate that reactions to auditory stimuli become disproportionately slower with advanced age14. That is to say, the average reaction times to visual and tactile stimuli show a similar magnitude of slowing between the ages of 20 and 80 years (ie 0.21 to 0.40sec and 0.26 to 0.47sec, respectively), whereas average reaction time to auditory stimuli is almost identical to that for visual stimuli from the age of 20 to about 50 but then slows much more rapidly, to around 0.53sec by the age of 80. Hearing for speech
The data described in the previous section gives a good indication of the changes in general hearing ability in elderly people. However, unlike for younger ‘normal’ hearing people, these audiometric measures are less able to predict for an elderly population, perhaps the most important aspect of hearing ability; the ability to understand speech. In general terms, the main limitation of these measures is that they miss one of the crucial aspects of the function of the auditory system with regard to speech perception15. That is, the extremely complex and informationally dense but transient nature of the speech signal. It has been indicated that when listening to normal speech, the ear may be
14
presented with as many as 30 phonemes a second. There is also the difficulty of explaining in terms of the acoustics alone, how, when versions of the same word, spoken in differing circumstances (or by different speakers, etc) share no acoustic similarities, they will nevertheless generally be recognised as versions of the same word. Because of this, much work on speech perception has used phonemic materials (rather than connected speech), which are often construed as the ‘basic units’ of speech. Some studies have used this material to obtain threshold levels16 while others have used similar psychophysical paradigms such as assessing ability to identify and discriminate between phonemes17. As well as phonemes, syllables have been used. An important review of the literature in this area cites studies that have used CV (consonant, vowel), CVC, VCV and CCVC syllables18. An additional complication in interpreting these ‘phonemic’ and ‘syllabic’ studies, is that, in general, the term ‘phoneme’ is used to indicate material that has been excised from recordings of ‘natural’ speech, while ‘syllable’ indicates the pronunciation of the letter groups in isolation. Further, in some of the literature there is some ambiguity as to the actual referents of these terms. The significance of this point is that different instances of the same ‘syllable’ tend to share more acoustic properties than do different instances of the same ‘phoneme’. Returning to ‘syllable’ material, the review mentioned above, points out that across the studies covered there seems to be a variety of opinions as to the relative importance (for perception) of consonants, vowels, meaningful or nonsense material and whether the letter groups appear in (or as) actual words. Hence, the general tendency has been to use real words. Although here too, there has been disagreement as to the primacy of the influence of factors such as: whether or not the set of words is phonetically balanced (ie represent the frequency of occurrence of all speech sounds in the language concerned), the frequency of usage of the words themselves, the syllabic length of the words and the number of other, similar sounding words in the language. Thus, it can be seen that there is little consensus as to the most suitable way to apply audiological principles to the measuring of hearing for speech. It is generally accepted however, that most of these approaches indicate age-related declines in hearing for small ‘units’ of speech. But, depending upon the specific approach and methodology used, the extent of this decline is claimed variously to be in accord with ‘standard’ audiometric data or to be significantly worse than the latter predicts. The use of real words however, inevitably introduces meaning to the situation and, in a sense, this is appropriate, because the most important aspect of hearing speech is extracting a meaningful message of some kind. However, although this brings us closer to speech understanding it is at the cost of losing any direct relation with basic auditory function. An important point here is that there is a variety of evidence for the somewhat illusory nature of (meaningful) speech perception in that, when listening for meaning we can consciously hear something other than our ear does. An often cited example of this is a
15
phenomenon called ‘phonemic restoration’ which is based on the finding that if a phoneme is removed from a recording of a spoken sentence and a silent gap is left, listeners have no difficulty detecting the gap’s presence and position19. If, however, the removed phoneme is replaced with a sample of the speaker coughing (or a ‘buzz’ generated from the same fundamental frequency) the missing phoneme is not detected and the listener will emphatically claim that the full word appeared. Further, it has been demonstrated that the context of the sentence can determine different perceptions of the same ‘cough/word section’ (eg ‘ ite’). For example, a boy going out on a windy day would be understood to be ‘... taking a kite’, whereas a hungry boy with an apple would likely be ‘... taking a bite’. This is a clear example of how loose the connection can be between what our minds and our ears ‘hear’ when listening to speech. Thus, it is apparent that as soon as hearing involves the extraction of ‘meaning’ from sounds there is a certain degree of reliance on related cognitive processes. Important aspects of these ‘higher order’ processes will be described in subsequent sections. However, there are aspects of speech perception which, although they are basically cognitive, are fundamental enough to be included in the present perception section. These aspects involve hearing speech in less than optimal circumstances. There is currently a degree of uncertainty over whether the age-related audiological changes described above are better characterised as generally reducing the ‘volume’ of the incoming signal, or as introducing more ‘noise’ to it. For present purposes it suffices to say that it is a bit of both. The point here is that age-related hearing impairment is not just a case of things seeming quieter but also of them being distorted (ie some elements of a complex sound being ‘quieter’ than others produce the effect of a different complex sound) and being embedded in ‘noise’ (created by deterioration of the hearing mechanisms themselves). These alterations to the incoming signal mean that older people are at a relatively greater disadvantage should the external listening environment involve further distortions and/or noise. A variety of research has indicated that this is indeed the case18. Thus, elderly people have greater difficulty hearing speech which is interrupted, reverberated, frequency band limited, ‘peak clipped’ or is embedded in; ‘white’ noise, ‘cafeteria’ noise, traffic noise, and in particular ‘irrelevant’ (competing) speech (and even more so, if this comes from multiple speakers). These effects have generally been identified in a context where the original (unaltered) speech was produced in a well articulated and clear manner but has also been found that (regardless of competing noise or distortion) elderly people have disproportionate difficulty understanding ‘poor’ speakers. Technological advances mean that a certain form of ‘poor speaker’ is becoming more prevalent. That is, currently even young ‘normal’ hearing people have been shown to have some difficulty understanding computer generated synthetic speech compared to natural speech. It seems this is mainly due to a paucity of knowledge as to the specific ‘rules’ underlying the generation of ‘good’ speech, such that it is generally accepted that synthetic speech lacks the redundancy of natural speech. In this context, redundancy is meant in the 16
sense of ‘That which can be omitted without any loss of significance.’20. Although the specifics are far from clearly understood (see above), it is generally accepted that speech is highly redundant and that the processes of ageing limit the older listener’s ability to capitalise on that redundancy, such that any further attenuation of redundancy imposed externally will make some degree of misperception almost inevitable.
Research by the present author21 has shown that another form of ‘distorted’ speech can have a negative impact on elderly people’s understanding. This research examined the effects of ‘low bit-rate’ speech, which due to limited bandwidth constraints, is digitised and the bit-rate (ie the transmission speed of the information specifying the speech wave) reduced from approximately 64kbps (kilo-bits per second) to just under 10kbps. This treatment of the speech had a marked negative effect on older people’s ability to perceive and understand it. Given the relatively slow processing speed of older people particularly for auditory stimuli, it is perhaps not surprising to find that they also have trouble if the speech they are listening to is relatively rapid. In the case of someone who is simply a ‘fast talker’ this will likely be due, in part at least, to relatively poorer articulation which has been associated with rapid speech. However, similar effects are found if the speech is artificially speeded (with pitch held constant). Some of the studies mentioned above have also included combinations of degradation to the speech wave. In general, it has been found that such combinations tend to have a negative impact that is greater than the sum of the individual effects. This seems to be due mainly to the changes in basic auditory function in combination with limitations in time related auditory processing ability.
Touch etc As in previous sections, the changes described below cannot be clearly delineated as being due solely to ageing per se, as damage and disease inevitable play a role too. For example, diabetes affects many older people and is known to also underlie some of these changes. There are a variety of forms of tactile perception which tend to have different sensorineural mechanisms supporting them. Only those with apparent relevance to the subject at hand will be described here. First, aspects of what is commonly considered ‘the sense of touch’ (somesthesis) will be outlined. This will be followed by an outline of certain aspects of kinesthesis, which is responsible for our sense of bodily movement (or stability) and orientation. One aspect of somesthesis is the ability to detect gentle pressure against the skin. Although the literature indicates enormous variability depending on the location and method of measurement, the general tendency is for touch to become less sensitive with age22. This is mainly due to the ‘receptor’ cells (meissner corpuscles) involved, becoming malformed, moving further from the surface of the epidermis and declining in number with advanced age. It also seems that these changes become noticeable slightly later than for vision and hearing at about the age of 60.
17
One measurement technique that has been relatively widely used involves pressing two pin-points in close proximity onto the skin and identifying the distance at which the points cease to be detected as separate sensations and become ‘fused’ into one. The shortest distance between the two points which can be detected as such is called the ‘two point limen’. The two point limen can vary within any individual, depending on the area of the body assessed. Pertinent here are the findings that indicate that various two point limens on the hand do increase with age. For example, in young people the two point limen for the palm is an average of 6.3mm, while for older people it is 7.8mm. Similarly, for the pad of the little finger, the increase is from 2 to 6mm, and for the pad of the thumb from 2.2 to 3.9mm (this is the main reason that many elderly visually impaired people have great difficulty reading Braille). Overall there is a greater decline in sensitivity to vibration, however, this is less marked for the upper than the lower extremities. Further, sensitivity to vibration is frequency dependant. Such that, frequencies below about 150Hz show slight, but reliable deterioration with age, while sensitivity to frequencies above these (usually up to about 600Hz) show a relatively greater decline. For kinesthesis, no evidence has been found for changes in the ability to detect passive movement (ie manipulation of joints, etc by an external force) and only sketchy evidence relates to changes in sensitivity to active movement. The uncertainty of this evidence is mainly due to the procedures used (eg bringing the tip of the index finger to the nose with eyes closed) as they often inherently involve elements of accuracy in motor control, which is known to be poorer in older people (this will be expanded upon in Chapter 4). A more complex form of tactile sensitivity, known as stereognosis, is the ability to recognise the form of an object solely from tactile inspection. This ability will involve most of the elements described above (and possibly others). Thus, it is not surprising to find that this also tends to deteriorate in later life.
While it is possible that future technological advances may raise their importance, at present the senses of smell and taste are not considered relevant here.
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Chapter
3
cognition
The experimental investigation of intellectual ability or ‘intelligence’ has a somewhat controversial past (and present, and no doubt, future). In large part, this is due to the fact that ‘intelligence’ is a word with a rather nebulous definition. In its general usage this is rarely problematic and most people know what is meant by the term. However, for scientific purposes, the measurement of any abstract construct requires much greater precision in the definition of that construct before scientific methods can be brought to bear on it. This introduces the first difficulty, such that an academic may publicly announce findings related to ‘intelligence’ (as specifically defined by a particular theoretical perspective) but this will be taken by the majority of people to relate to their more generalised understanding of the word. This kind of miscommunication between scientists and the public is quite commonplace but most often it is ultimately inconsequential. However, as the generalised definition of ‘intelligence’ includes many connotations which are often highly emotive and seen as socially important, the outcome of this particular miscommunication is far from inconsequential. To illustrate this point, take a moment to consider the difference in the likely public reaction to a renowned scientist claiming that group A is more intelligent than group B, compared to the claim that group A has better hearing than group B. Despite these and other (eg methodological, philosophical and theoretical) difficulties, the psychological investigation of ‘intelligence’ has made many advances. Also, although ‘intelligence’ research continues to involve (often heated) debate over an ‘ultimate’ definition, the results of these endeavours have offered valuable insights for understanding some of the more basic constituents of ‘intelligence’, such as thinking, learning, problem solving, remembering and forgetting. Examining these smaller scale ‘mental faculties’ allows for greater precision in their relevant definitions, and there is also the advantage that they can be referred to in the context of (the less commonly used and more ‘neutral’ term) cognition.
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With regard to ageing, a microcosm of the ‘intelligence’ controversy mentioned above, developed within the academic psychology community. In simple terms this started with claims to the effect that elderly people were ‘less intelligent’ than younger ones. This led to a variety of research aimed at countering this view (and also at supporting it). Although many aspects of this debate continue, the outcome is (for present purposes at least) that it is generally agreed that some elements of ‘intelligence’ (cognitive abilities) do show a tendency to decline with age and some do not.
‘Crystallised’ and ‘Fluid’ cognitive abilities Basically, this distinction emerged from studies of ageing and ‘intelligence’, which employed factor analysis of the data and indicated that different items in ‘intelligence’ tests could be statistically grouped as either ‘age sensitive’ or ‘age robust’23. The nature of the test items involved led to these groupings being labelled ‘fluid intelligence’ and ‘crystallised intelligence’ respectively (hereinafter referred to as fluid and crystallised abilities or processes). While there is some heuristic value (particularly for those without a background in cognitive psychology) in considering these different types of cognitive ability as a dichotomy, strictly speaking it is more accurate to consider them as reflecting the extremes of a dimension. At one extreme are abilities that are generally maintained (or even improved) into later life. An example of this type of measure is the Mill Hill vocabulary test24 which has been found to remain fairly stable in later life4. At the other end of this dimension are abilities that decline with advanced age and involve the kind of ‘puzzles’ commonly associated with ‘IQ’ type tests. An example of this, used in our laboratory is the AH4 part 225 and this measure has been shown to decline with advanced age4. Representative items from these two tests are given in Example A below. In this somewhat over-simplified context it can be said that ‘crystallised’ abilities reflect accumulations of stored knowledge, and that ‘fluid’ abilities reflect the manipulation or ‘processing’ of information. It can be seen that this description lends itself to a ‘computing’ metaphor of cognition. That is to say, the ‘crystallised’ knowledge is like the data on a hard disk which can be added to as new instances are encountered, whereas ‘fluid’ ability is like the processing power of the central processing unit (CPU). It has generally been found that ‘fluid’ abilities tend to decline with advanced age, whereas ‘crystallised’ abilities tend to be more robust and can even continue to improve into very old age. As mentioned above however, this dichotomous view is somewhat misleading. That is, it is apparent that the example test items above are exceedingly
20
contrived and as such do not really represent ‘real world’ cognitive tasks which people tackle (eg working out how to use an interactive TV system). In other words, most cognitive tasks that people encounter in their day-to-day lives lie somewhere between the extremes of this ‘crystallised/fluid’ dimension. For example, even a vocabulary test like the one above requires not only that the relevant word be there but also that it be found, compared with synonyms, or definitions and that information appropriate to the required response be retrieved and acted upon. Similarly, the ‘fluid’ examples require some form of stored knowledge even if it is only something as apparently trivial as understanding the instructions and remembering what to do with the stimuli.
Example A: Selected items from the ‘Mill Hill’ and ‘AH4’ tests.
The ‘Mill Hill’ test involves identifying the synonym for each of a series of increasingly obscure words; (Answers in parentheses below) ANONYMOUS applicable magnificent insulting nameless fictitious untrue (nameless)
PALLIATE regenerate qualify alleviate imitate stimulate erase (alleviate)
The ‘AH4 part 2’ test involves ‘non-verbal reasoning’ to select the correct answer from a set of options; (Answers in parentheses below)
(5)
(2)
Another useful insight which has emerged from ‘intelligence’ research is the finding that tests which emphasise speed or have specific time constraints tend to produce the biggest differences between old and young people, while those that do not have such restrictions tend to limit (and in some cases remove) such differences. This provides another useful heuristic when considering older users.
The ‘general slowing’ hypothesis
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Although in a strict theoretical sense, the ‘hard’ version of the ‘general slowing’ hypothesis is markedly flawed, a ‘softer’ version provides a useful framework for understanding the difficulties older people can face in day-today cognitive tasks26. As the name suggests, this view considers the main cause of age-related decline in cognitive ability to be that older people effectively process information more slowly than younger ones. This is based on various findings from physiological measures of the peripheral and CNS and from experimental cognitive research. The ‘hard’ version of this view suggests that for a given task, older people perform precisely the same (‘fluid’) cognitive processes as younger people, only slower. However, the changes in sensory/perceptual function indicated in the previous chapter, strongly suggest that older people effectively have more to do than younger ones. That is to say, while older people may well have a slower cognitive system, that system also has to deal with deteriorated (or more ‘noisy’) sensory input. An illustration of this point comes from studies which (simply stated) showed that levels of white noise (or relative deafness) which did not affect volunteers’ ability to correctly identify spoken words, did in fact, negatively affect subsequent recall for those same words, even though all words in the recall task had been repeated correctly27, 28. This was interpreted as a ‘knock on’ effect, caused by additional (‘fluid’) cognitive resources being required to successfully extract the speech from the ‘noise’ (either external or internal) in order to allow adequate intelligibility, with the consequence that inadequate resources were available to fully rehearse and otherwise elaborate upon the target items (hence, poorer recall). Thus, regardless of whether these age-related declines are due to slower processing, to more processing or even a combination of both, the point here is that all human cognitive systems have a finite amount of ‘fluid’ processing resources available at any given time. Such that, the more demanding a cognitive task is, the more thinly spread these resources become. This means that for older people there is a greater tendency that there will ‘not be enough to go around’, leading to errors and other forms of ‘failure’.
Attention Attention is another aspect of ‘fluid’ ability. However, like ‘intelligence’, ‘attention’ is a word in common usage which has a ‘general’ definition which is often at odds with that (or rather, those) used by cognitive psychologists. A completely adequate description of attention (not to mention the age-related changes) is well beyond the bounds of this document but some of the more general, relevant principles will be outlined here. One aspect of age-related changes in attention relate to the amount of information that can be attended to at a given time. It is known that such
22
attentional ‘capacity’ can vary widely between (and within) people depending on factors such as; familiarity with the task, general motivation, fatigue8. For the sake of brevity it suffices to say here that (following the ‘limited resources’ argument, above) elderly people tend to have greater difficulty ‘taking in’ the same amount of information in unit time. Another aspect is the ability to ‘do more than one thing at a time’, such as driving a car while talking to a passenger. Differing theoretical views describe this variously as ‘divided’ attention (ie both ‘tasks’ are attended to simultaneously) or ‘selective’ attention (ie each ‘task is attended to alternately, in rapid succession). Following the same principles as outlined above, if the two (or more) tasks involved are relatively taxing (eg talking and driving) then older people are more likely to show a detriment in performance of one (or both), however, with relatively ‘easy’ tasks (eg walking and chewing gum) then it is more likely that no detriment will emerge. In addition to these quantitative differences in attention with age another change can have a more qualitative effect. Again, glossing over the details for the sake of clarity, this difference can be characterised by the claim that older people have more difficulty ignoring ‘irrelevant’ information. On the one hand, this can have a quantitative effect, such that the processing of ‘irrelevant’ information means relatively less ‘fluid’ resources available for the ‘relevant’ aspects of the task. On the other hand it can also have less predictable qualitative effects, such that ‘irrelevant’ information may be incorporated into an (erroneous) solution. Another change in attention relates to the rapidity with which it can be ‘switched’ between differing ‘views’ of a perceptual ‘scene’ or a cognitive ‘concept’. This issue also happens to represent a good example of the ‘grey area’ between ‘perception’ and ‘cognition’. One approach to this ‘switching’ ability employs visually ambiguous figures (see Example B below) which can be ‘seen’ in more than one way. People will usually see one or the other of the possible ‘scenes’ initially but once they have ‘seen’ both they can switch between them virtually ‘at will’. It has generally been found that older volunteers tend to show less ‘mental agility’ in this regard.
Example B: Samples of commonly used ambiguous figures.
The picture at top right can be ‘seen’ either as a young or an old lady29. The interchangeable reference points are; the young lady’s cheek bone and jaw line/the old lady’s nose, and, the young lady’s ‘choker’/the old ladies mouth. It has been shown that older people had increased difficulty initially seeing the alternative scene to their ‘preferred’ one and were slower in making switches between them once they had 23
‘seen’ both30. Similar findings have emerged from studies using ambiguous geometric figures such as the ‘Necker cube’. A commonly used form of this can be seen on the right and the alternative ‘scenes’ depend upon which of the cube’s faces is designated as being at the ‘front’ (the two smaller examples show the ‘front’ face in bold). This form is usually seen spontaneously as ‘a picture of a cube’ by people of all ages, whilst the variation shown at the bottom is more likely to be seen as a 2D geometric figure until suitable prompting is given. It has been shown that not only do older people have more difficulty switching between the possible views (and in some cases are apparently unable to), but they also tend to have more difficulty ‘finding’ them, particularly in the case of the ‘2D’ version31. Analogous difficulties have been shown at the level of ‘concepts’ rather than ‘percepts’. An indirect example comes from a study which examined ability to ‘edit’ memory. Volunteers were presented with a sequence of ‘messages’ which built up stages of a coherent ‘story’32. One of the last messages however was a correction of an earlier message. Salient here was the finding that volunteers with ‘low digit span’ scores (see working memory section below for a description of this measure) showed a slight decrement in memory for the ‘list’ of messages and their content (but usually remembered the correction message). However, these volunteers showed a disproportionately large decline in their ability to ‘edit out’ the information now known to be erroneous. That is to say, when asked to recount the overall story they tended to continue to draw inferences from the information which they knew (had recalled) to be incorrect. Although this study did not involve an age comparison, it is known (see below) that older people tend to have ‘low’ digit spans. In a similar vein studies have been described which examine age differences in cued recall. ‘Cued recall’ involves learning a list of paired items, followed by a test in which one of each pair is presented as a cue for the recall of its paired ‘target’ item. It has been shown that age differences in performance on these tasks are minimal if the (cue-target) word pairs are strong associates (eg chair-table) but that differences are larger if they are not (eg chair-moon)22. Further, if the list (as a whole) contains pairs of strongly associated words (eg flower and blossom; hot and cold) but the cue-target links do not connect them in this way (eg flower-cold; hot-blossom) then older people’s cued memory performance is worse still. It has also been suggested that more complex concepts, such as
24
the instructions for a laboratory cognitive task are more easily misconceived by older people and that, once such a misconception has been developed it is relatively more difficult to correct.
Working memory Virtually all cognitive tasks will at some point require the use of ‘working memory’ which involves ‘juggling’ items of information such as when doing ‘mental arithmetic’. ‘Working memory’ has been described as ‘the interface between memory and cognition’33. To clarify this, take the example of mental arithmetic; ‘long term memory’(LTM) is responsible for ‘knowing’ what the digits and symbols ‘mean’. ‘Short term memory’(STM) is responsible for holding the equation in mind. Generalised ‘fluid’ cognitive processes (see above) apply the mathematical rules (supplied by LTM), while working memory updates STM with partial solutions (including ‘remainders’ and ‘carry-overs’, etc) and also monitors such updates, so that stages are not omitted or duplicated. (NB this is something of an over-simplification as there is no clear cut distinction, particularly in this example, between ‘fluid’ processes and working memory.) Another example, involving age-related changes, may help to further illustrate this point. A commonly used measure (mentioned above) which reliably shows a moderate decline in advanced age34, is ‘digit span’ which refers to the largest number of randomly ordered digits a person can repeat in serial order immediately after a single verbal presentation. A closely related measure is ‘reverse digit span’ which is basically the same test only the subject must repeat the digits in reverse serial order, which requires working memory to ‘juggle’ the digits into the new order. This measure shows relatively greater decline with age.
Recall and recognition As mentioned above in relation to ‘crystallised’ abilities, there is little evidence to suggest deterioration of information stored in long-term memory in ‘normal’ ageing (the various forms of dementia notwithstanding). However, it is well known that for all people it is usually much easier to remember information when memory is tested by recognition rather than by recall. It has generally been found that this differential increases with age22. Although claims have been made to the effect that; recall declines with age while recognition does not, research from this area presents a somewhat more complicated picture. The important point here is that there is no absolute distinction between ‘recall’ and ‘recognition’ and as with the other ‘distinctions’ outlined above they more 25
realistically represent the extremes of a continuum. In this instance it is the ‘usefulness’ of the cues to target items that varies along the dimension and findings suggest that the ‘stronger’ the cue the less the likelihood of an age effect emerging. In other words, tests of recall tend to be characterised by only very ‘weak’ cues, such as ‘please write down as many words as you can from the list you just heard’ or ‘what did you do on 6 April?’. Whereas, recognition tests would involve much ‘stronger’ cues such as ‘can you mark the items on this list of words which are the ones you previously heard’ or ‘On 6 April did you go to work or to the beach?’ In the latter examples the ‘strong’ cues can also be termed ‘copy’ cues in that a duplicate of the target is presented so that, rather than having to ‘generate’ an answer the task is a decision based on the familiarity of the copy cue. Various test procedures have been devised which occupy the intervening points of this dimension, findings from which suggest that ‘stronger’ cues are ‘better’ for older people. There is, however, an additional complexity about recognition performance that is worthy of consideration. This relates to the nature of the ‘distracter’ items from which the familiar target items must be distinguished. Take for example a ‘normal’ recognition test where a list of 20 randomly chosen words are presented followed by a test list of similarly random words, 10 of which were presented initially and 10 were not. This represents the kind of situation where age effects are minimal35. Compared to this, performance would, in general, be relatively worse (and age differences relatively larger) if at the test stage instead of random words, the distracter items were ‘paired’ with each target item using a semantic relation (eg seat-chair, look-see, etc). Taken to its extreme, this sort of experimental manipulation can even produce ‘false’ memories. An example of this comes from research into memory for word lists36. Volunteers were given lists of 12 words to study, for each list the words had been carefully selected as strong associates (eg bed, rest, awake) of a ‘critical’ associate (eg sleep), which was not presented in the list. Subsequent recall tests showed that the ‘critical’ associate was as likely to be ‘recalled’ as many of the actual target words. Further, it was found that volunteers who had falsely recalled the critical associate in the first test, also ‘recognised’ it in a second test and that this false recognition was as likely as correct recognition and was made with equitable levels of subjective ‘certainty’. Research (as yet unpublished) in our laboratory has indicated that older people can often be even more susceptible to this phenomenon (depending on the nature of the ‘deception’ employed) and show a relatively greater likelihood of false recall and of false recognition (even without the preceding false recall), again with high levels of certainty. This, taken together with the tendency toward ‘mental rigidity’ (eg reduced ‘switching’ ability, etc) mentioned above, strongly suggests the importance of ensuring that older people get clear and unambiguous instructions (etc) at the outset, because once a misconception has been developed or erroneous inferences drawn, it can prove extremely problematic to get them ‘back on the right track’.
26
Bi-modal augmentation/interference Several studies have found that older people have difficulty integrating and remembering information from more than one channel37, 38. Recent work suggests that this may sometimes be true even when the information on one channel simply replicates that given on the other. For example, it has been found that young adults recalled more information from a passage of text when they simultaneously read it and heard it39, 40. However older volunteers did not benefit from this replication of information. Another example that older people have difficulty integrating visual and auditory information was indicated by a study which required volunteers to watch video recordings of four successive statements, which were either all made by the same person or were each made by one of four different people28. Volunteers of all ages could recall the content of the four statements equally well in all conditions but, in the four speaker conditions, older volunteers had relative difficulty in correctly remembering which speaker had made which statement (‘source’ memory). A further demonstration of this difficulty comes from an (as yet) unpublished study carried out in our laboratory for the EC’s RACE ‘Tudor 1088’ project, examining the possible benefits of videophones to older users. One obvious benefit of a videophone is that if users can see a person they talk to for the first time, they will be able to recognise them when they talk to, or meet them again later. To examine the relative effectiveness of faces and names as cues, elderly volunteers were ‘introduced’ to sets of four ‘men’ with a slide showing a photograph of their face and/or their name (eg Mr. Walker) accompanied by a verbal description of three items of biographical information (ie their occupation, a possession and a hobby). After each set of four different slides had been presented and described, the elderly volunteers were cued to recall as much biographical information as possible about the imaginary personalities described. Their recall was cued by three different types of cue; the person’s name alone; their face alone, or both their face and name. This cued recall occurred under two conditions, in one volunteers knew beforehand which cue type would be used for recall of that set, in the other, cue types varied unpredictably. Findings from this general area of ‘dual coding’ research suggest an hierarchy of cue efficiency, with the most powerful cue being the face and name, followed by face cues, with name cues being the least effective41, 42. However, for our elderly volunteers recall was significantly better for face cues than for face and name cues, although as expected, name cues were least effective of all. This pattern held regardless of whether or not volunteers knew in advance which type of cue to expect (although the ‘informed’ condition produced better performance than the ‘uninformed’). It would seem that the additional demand of remembering both faces and names as cues (and possibly of associating these to each other), reduced the total amount of information which could reliably be reported.
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In contrast to this, are findings from studies evaluating an ‘audio-description of television’ services43. On the basis of the findings above, there was a degree of concern about the possible impact of an extra verbal channel replicating visual information, on a sighted elderly audience (although this service was primarily aimed at blind and partially-sighted people, the visual declines of the elderly population involved them as an important element of the target audience). One series of experiments indicated that in general most older people showed improved comprehension for ‘described’ rather than ‘undescribed’ (ie normal) programmes and none were found to suffer a negative impact. However, this finding is tempered by that from subsequent experiments which manipulated the amount of audio-description given. The general finding here was that the difference between ‘no description’ and a ‘minimal description’ was similar to the above. Whereas, the difference between the latter and a ‘maximal (or ‘verbose’) description’ was more complex. That is, overall performance was the same between these conditions, however, further analysis of the data showed that behind this average was a differential between elderly volunteers with relatively high or low ‘fluid ability’ scores, such that ‘high fluid ability’ volunteers showed further benefit from the additional verbal information, while ‘low fluid ability’ volunteers seemed to suffer an ‘overload’ and tended to show poorer comprehension than they had for the ‘minimal description’ version. Taken together, the above indicates the caution that is required in the amount of information that is presented to separate sensory modes, in unit time. As, on the one hand, it may well ‘augment’ understanding (etc) but can very easily ‘interfere’ with it too.
Interrelatedness of perception and cognition This and the previous chapter have described the sensory, perceptual and cognitive changes associated with ‘normal’ ageing. The distinction between these topics was maintained for the sake of brevity and ease of exposition. The sensory and perceptual aspects were presented first as, in a simple sense, these are what provide the ‘input’ for cognitive processes. However, it has been mentioned where relevant above, and is worth explicit mention here, this ‘flow’ of information from the senses to the cognitive systems is not a one -way street. One aspect of this is that varying amounts of cognitive resources can often be ‘commandeered’ for the ‘preprocessing’ of sensory information, leaving fewer available for the requirements of other concurrent processes, often of a more ‘intellectual’ nature. Further, the amount of ‘preprocessing’ required can be affected by the ‘efficiency’ of the cognitive systems which dictates the focus of attention. That is, if the cognitive systems have not capitalised on prior information in order to focus attention appropriately, then more ‘searching’ will be required which means that relatively more ‘irrelevant items’ will require ‘preprocessing’ only to be rejected. Thus, in general, greater clarity in presentation will allow greater amounts of older people’s already limited cognitive resources to be ‘freed up’ and brought to bear on the more ‘intellectual’ elements of the task in hand.
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Similarly, the more clearly an older person understands the general procedure and specific steps in an interaction the greater the chance they can ‘predict’ what will happen next, and the more accurately these expectations are met, the less the likelihood they will misperceive some important element of information. Such misperceptions, particularly when incorporated into a (subsequently erroneous) concept or ‘plan’, can also prove very difficult to correct.
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Chapter
4
other individual differences
Motor function It can generally be claimed that motor function declines with advanced age. However, like the changes mentioned so far, changes in motor function are as much characterised by wider variation throughout the population as by ‘average’ declines. A review of this area of the literature reveals that it has several limitations which reduces the amount of guidance that can be gleaned for an elderly population of users of the types of control devices likely to be associated with interactive television services. First, there is the issue of the types of bodily measures generally covered in anthropometric studies. That is to say, the standard categories of measures are not dimensions immediately relevant to the use of hand-held control devices of the type relevant here. Many of the measures included in these studies are static such as upper/lower arm length and hand/finger length, etc. It can be seen that while such measures are fundamentally important for certain aspects of design they are rather far removed from the aspects directly involved in manipulating a hand-held control device. Although some dynamic measures are also included in these studies, these tend to be equally wide of the mark for present purposes, mainly because they are based on measures important for various aspects of the (industrial) work place (eg maximum grip strength). Thus, while there is some information regarding the ‘size’ and ‘strength’ of older people, there is virtually none regarding their ‘precision’ and ‘dexterity’. Another major limitation of this corpus of literature relates to the extent to which the elderly population is represented. This situation is succinctly described thus; ‘The elderly are recognised as a distinct population anthropometrically..., but this recognition has not yet resulted in appropriate representation in anthropometric studies.’44. Further, studies which have included older people have limited the utility of their reported measures by treating all older people as one group. That is, most studies separate the population into relatively small age groups (particularly those
30
under 20 years) up to around retirement age but then tend to have a final ‘catch-all’ grouping, usually labelled ‘65 years and older’. This has several unfortunate consequences, one of which is that this helps to perpetuate the myth that elderly people constitute an homogenous group in which any older person shares much less in common with a younger person than they do with any other older person (this usually in a context of cultural stereotypes). This perspective is likely to be misleading as it is known, particularly in the areas of cognition and sensory physiology, that while there may be a decline in some ability with advanced age, this is a decline in the mean (average) score45. Although it is possible that a change in a group’s mean score may reflect the same degree of change in all members of that group, it is generally found in elderly groups that a change (decline) in the mean reflects a widening in the variance of that group’s scores with the ‘best’ maintaining a level of performance on a par with the ‘best’ in a younger group. While the ‘worst’ show a disproportionately large decline compared to the ‘worst’ of a younger group. It is also generally accepted that associated with wider variation in an elderly population is the tendency for the distribution of scores within this range to deviate from a ‘normal’ (bell shaped) curve which further limits how well a mean score represents the whole group. A final, important limitation of most anthropometric studies is that where an elderly group is represented it is usually by a sample of older male workers. This group is very unlikely to realistically represent the wider population, partly because they are very likely to differ from similar aged males who have not continued working into later life and partly because it is well established that in the wider population, there are fewer older males than females and that this imbalance becomes greater as age increases.
Cohort/cultural differences Beyond ageing per se, it is important to recognise that older people differ from younger ones because they come from different generations. One fundamental aspect of this is that the current older generation grew up with technology that was predominantly mechanical, whereas today’s younger generation are surrounded by technology that is predominantly solid-state. The extent of these differences are likely to diminish in the coming years as prospective generations of elderly people will become more likely to have grown up with information technology. The relevance of this here is that, in general, mechanical artefacts work in a way that can be ‘seen’ and fairly readily understood. In contrast to this, solidstate information technology effectively works ‘by magic’ to anyone without a relatively high level of expertise. In a sense, those brought up with this ‘magical’ technology soon take it for granted and consequently cease to see it as ‘magical’. On the other hand, those brought up with mechanical technology are much more likely to find their (often implicit) understanding (of analogous mechanical processes) at odds with a piece of modern
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technology and will thus be reminded more often that it is indeed ‘magical’ or more to the point, beyond their understanding (and control). Another aspect of this point was described in the previous chapter where it was indicated that older people can have relatively greater difficulty rejecting previously learned concepts and replacing them with newer ones. This somewhat abstract point is relevant here because it can often manifest itself as a strong inhibiting factor in elderly people using information technology. That is to say, a ubiquitous concern seems to be that if they do not carry out precisely the correct operations they will ‘break it’ (see Example C). This (generally unfounded) fear seems to be compounded by the fact that most ‘hi-tech’ equipment is specifically designed to give an appearance of complexity (ie to the older user, it is a lot easier to get something ‘wrong’ and thus ‘break’ it). This situation is further compounded by widely held stereotypes of older people (which are unfortunately often held by older people themselves), such as them being ‘technophobic’ and the belief that ‘hi-tech’ systems are really only for young people. The general idea that older people are ‘no good with’ and/or ‘not interested in’ new technology is explored more thoroughly in the next section of this chapter.
Example C: Anecdotal evidence that ‘one wrong move will break it’.
One of the present author’s first experiences of cognitive research with elderly people involved a ‘reaction time’ study. Simply stated, volunteers were required to react as quickly as possible to a fairly rapid sequence of stimuli by pressing one or other of two keys on a PC keyboard. The volunteers sat with each index finger poised above the keys in question to minimise movement time (the object of the study was to examine possible reaction time differences between responses made by the same hand as that which had previously responded and those made by the other hand to that which had just responded). One female volunteer in her mid-70s, despite repeated instructions to respond ‘as quickly as possible’, seemed to be deliberately pausing before each response. At the end of the session she was asked about this tendency to pause, and it soon became apparent that she had been a typist (and had only ever used mechanical typewriters) and that she did not want to hit successive keys too quickly in case she ‘jammed’ the keyboard. In addition to ‘ageist’ stereotypes, there also seems to be a common belief that most of the problems older people may have with ‘hi-tech’ equipment in their home can readily be solved by a younger family member or neighbour. To the extent that this assertion is true, there is a limit to how ‘helpful’ this kind of support tends to. That is to say, that while the problem gets solved for them, they will probably be in no better position to solve it for themselves next time. Thus, an (albeit small) element of dependency is maintained (which on a social basis may be desirable for the older person concerned), but perhaps more importantly, each time this happens the idea that they cannot do it is reinforced. Yet it has been shown that with a suitably designed interface and a minimum of ‘training’ older people can successfully (and enjoyably) use something as apparently complex as an internet-style information and communication system46.
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Perhaps the more important limitation of the view that ‘a younger person can help out’ is the somewhat unfortunate point that for many older people this is not an option. In general terms, the cause of this is often referred to as ‘social isolation’, however, in the social sciences this term can be problematic to use in a similar way as described in Chapter 3 for the term ‘intelligence’. Rather than attempt a definition of this term, it will suffice to present some figures from a recent review of demographic surveys involving the elderly population47. For example, it has been found that of all households in Britain, the percentage occupied by one person of pensionable age has risen from 7% in 1961 to 16% in 1989 (a trend that is expected to continue in the foreseeable future). A survey from 1988 showed that of those aged 65 to 74, some 27% lived alone (which breaks down to 17% men and 36% women) and that of those aged 75 years and over, 50% live alone (29% men and 61% women). Another perspective comes from a survey carried out in 1985, which showed that of those aged 65 years and over, 36% lived alone, 45% lived with their spouse only, 7% lived with their spouse and other family members, 3% lived with siblings, 7% lived with sons and/or daughters and 2% lived with ‘others’ (this latter mainly represents those living in institutions of one sort or another). This indicates that the vast majority of older people do not have a younger person immediately on hand to help out. Further to this another 1989 survey investigating ‘social contact’ among the elderly population, indicated that while many people over 65 were visited regularly by family or friends, 25% of them were visited either ‘less than once a month’, or ‘never’. It would seem then that while there are a ‘lucky few’ who can readily recruit help from younger people, most older people would effectively have to fend for themselves. Finally, in this section, whether or not it is related to ‘social isolation’, it has been argued that there is a relatively high incidence of depression among elderly people48. This is a debatable issue, partly because of definition difficulties (again), partly because of the wealth of issues related to its diagnosis and partly because of ‘statistical’ problems (eg women tend to live longer than men and [diagnostic issues notwithstanding] women tend to be twice as likely to be depressed as men). However, it has been estimated that around 25 to 30% of people over 65 are depressed. The relevance of this is that it has been shown that even mild levels of depression can have a negative impact on cognitive performance and that the most likely direct cause of this is reduced levels of motivation22. Reduced motivation can produce various other barriers to older people using new technology. For example, they are less likely to show levels of enthusiasm that they might otherwise. This will be a generalised phenomenon, but given the stereotypes outlined above, will likely be manifested more strongly with regard to new technology (including technology which has the potential to improve their situation, such as that used in the ‘internet’ study indicated above which showed that the elderly volunteers very much enjoyed and valued the ability to ‘email’ their friends as regularly as they liked, even if the content was generally inconsequential49. Another important consequence of depression is the tendency for feelings of self-inadequacy. That is to say, faced with an interface which is not self-explanatory, an error of some form is likely for any user. A user who has faith in their own competence will most likely react to this situation on the basis that the problem
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lies with the system and will probably persevere. On the other hand, a person with less faith in their own competence (or even active feelings of incompetence) will likely react on the basis that they are the problem (not this ‘clever’ system) and will probably give up, and will likely feel even more convinced than before, that ‘hi-tech’ equipment is beyond their grasp (see Example D)
Example D: Even apparently non-depressed elderly volunteers are ready to blame themselves rather than the system, even though most of the errors were due to inadequate on-line instructions.
A ‘natural history’ assessment carried out by the present author (outlined in earlier chapters) involved post-session debriefings to compliment objective measures of performance with volunteers’ own feelings about using this set of interactive services. The following quotes reflect the range of attitudes regarding where they felt the ‘weak link’ was (ie themselves or the system). Some volunteers reflected the stereotype that they were simply ‘not up to it’. ‘Makes me feel thick.’
‘I feel like a dunce.’
‘Is everyone as bad as me?’
‘You've got the wrong person here.’
Others indicated the same basic feeling but had a more optimistic tone. ‘I think I'll like this when I get used to it.’ ‘You need to be used to using remote controls and operating videos, I’ll have to make an effort to learn about these things and get some practice.’ Some however, did indicate the weakness was with the system rather than themselves. ‘Needs step-by-step written instructions.’ ‘Far too complicated, too much to remember at one time.’
Expectations and acceptance of new technology There is a variety of research that has examined the factors influencing user acceptance of new technology50, 51. In general, the findings vary depending on the user population and the type of technology involved but in any case, the relationships that are found tend to be complex and interdependent. In the case of an elderly user population the relationship between factors such as attitudes toward technology, perceived usefulness and acceptance of that technology are just as complex, yet an overriding factor which negatively affects user acceptance has been identified52, 53. That is to say, the elderly population will show a strong tendency to reject new products which have apparently been designed to cater to some kind of ‘special need’, as many elderly people do not want to be considered as being distinct 34
from the rest of the population. This phenomenon has been called the ‘difference factor’ and is accompanied by the statement that; ‘companies must devise marketing strategies that convey the benefits of a product without giving seniors the impression that the product will make them look or feel different from others’53. Thus, provision of ‘products’ such as interactive television services is more likely to attract elderly users if it is offered with a wide choice of ‘optional extras’ from which customers can choose as they see fit (perhaps with some degree of guidance). In other words, people with no limitations in their ability could choose on the basis of purely aesthetic or other idiosyncratic criteria and although the choice of those with limitations may be rather more constrained, they are still, to any outside observer, exercising ‘normal’ consumer choice and are thus not being identified as ‘different’. Given these problems, human factor designers need a methodology to predict how well older users will accept new systems. An obvious first step is to consider precisely what sensory and cognitive demands the prospective system will make. These demands can then be assessed in terms of what is known about the incidence and relative degrees of severity of these changes within the populations for which the system is intended (see Chapters 1 to 3). This first step is essential, but insufficient. It is also important to discover what these potential users feel that they actually need and what they are likely to expect from the service being offered to them. This is also essential because even if a system can potentially meet the demands of a particular elderly population, it does not follow that they will spontaneously and completely recognise its advantages and, thus, enthusiastically welcome it. It is an unfortunate characteristic of new technology that it is almost never completely transparent to novice users. People need to invest time and effort to realise the potentialities of such systems. This indicates the necessity of a clear idea of precisely what problems potential users will have in mastering a new system. The extent to which the target population can perceive the advantages that a system offers them as real and substantial, will increase the chance that it will be seen to merit the necessary investment of time and effort to learn to use it to its full potential. It is an unfortunate axiom among designers that older people are too easily intimidated by new technology, or have grown ‘too rigid’ to use it. Beyond the general limitations outlined above, this is simply untrue. A European Commission survey, carried out in collaboration with our laboratory, examined the extent to which European Union citizens saw advantages in the new communications technologies imminently available to them52. To do this, answers were obtained from questionnaires completed by 3,229 disabled and 2,790 able-bodied elderly individuals from four member states of the European Union (Portugal, Holland, Sweden and the UK). The questionnaires were designed to elicit information about the extent to which people in different age groups, and with different kinds of physical and sensory disabilities, used the telephone systems available to them, the
35
extent to which they felt the need for currently available extensions to the capabilities of these systems and the extent to which they would welcome new technology that superseded these systems. A first discovery was that people with different types of disabilities had very different attitudes to new technology. The extent to which they looked forward to new technology, were confident of their ability to make use of it and were willing to invest resources to acquire and master it, depended, of course, on the particular type of disability from which they suffered, and also the extent of the perceived improvements that such technological innovations might offer. However, it equally depended on their current interest in, and reliance on, new technology. For example, individuals with speech difficulties, who had become accustomed to the use of new communications systems to run their lives and maintain their social contacts, looked forward very eagerly to further innovations that might also benefit them. Other groups of the disabled, who had little or no experience of new communications technology, were less enthusiastic about potential new developments although they could clearly articulate what the advantages might be. The questionnaires were also analysed to examine the common assumption that older people are not interested in new technology or are, even, ‘technophobic’ and uneasy and afraid of it. The volunteers answered questions on their potential interest in particular items of imminently available technology such as videophones and home banking systems. To interpret their attitudes in terms of their current knowledge of technology they were also asked to describe the extent of their experience with examples of recently developed pieces of electronic equipment such as compact disk players, video recorders, home computer systems and extended facilities on currently available telephone systems. Initial examination of this data from 2,180 of the (able-bodied) elderly respondents did, indeed, seem to indicate that the degree to which they consider that new technology would be useful to them, declined sharply with their average ages. However, much of this overall trend was due to the sub-group which had little or no experience with commonly available electronic equipment, while the (somewhat smaller) sub-group with high levels of experience showed no decline. Indeed, a multiple regression analysis showed that when the highly significant effect of level of experience with current technology was taken into consideration, chronological age taken on its own, did not predict attitudes to new technology. The message from this is that although most people currently aged over 60 are less interested in new technological developments than are young adults, this state of affairs will not continue for long. People who are now in their 40s and 50s already have considerable interest in and competence with information processing devices and communications systems. It seems reasonable to expect them to maintain or even to increase this interest as they pass into their 60s and 70s, and begin to experience social or functional limitations for which new devices may offer solutions.
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Because questionnaires are so easy to design and administer, and because they can give us useful information about individuals’ interests and potential capabilities (regarding systems which they may not be particularly familiar with), they seem to offer an overwhelmingly powerful and convenient methodology for human factors designers. It is tempting to assume that older people are the best experts on the difficulties that they are likely to experience. If we ask the right questions surely they can provide comprehensive and detailed information on how to design new systems for them? Limitations of questionnaire data
It has been very unfortunate that elderly and disabled people have been so excluded from active participation in the early stages of design of equipment which is intended to meet their needs. However, a large body of work shows that, when evaluating data from people of any age, the precise wording of questions is critical, and that interpretation of questionnaire data requires continual intellectual vigilance. In order to get people to reliably assess or predict their own competence, great care is required to ask them very specific questions about the particular functions or skills we wish to evaluate, rather than general questions about their global competence in everyday life. The realisation that laboratory simulations cannot accurately probe people’s competence in complex everyday tasks led psychologists to develop ingenious questionnaires designed to elicit self-reports of lapses of memory or attention in everyday life54, or the relative frequency of specified categories of cognitive failures55. It did soon become clear however, that while these questionnaires had reasonable reliability, in the sense that individuals tended to give the same answers on separate occasions, their validity in predicting actual performance, was questionable (and no apparent improvement over that of laboratory experiments). That is, there was no evidence that the levels of everyday competence that people expressed in these questionnaires predicted their performance on global tests of everyday memory and cognitive competence56 or, indeed, on more specific laboratory tasks57. The lesson from this is not necessarily that people’s self-evaluations are unreliable, but rather that human competence is intensely domain specific. A person may have remarkable ability on one task but perform poorly in other, apparently quite similar, situations. A different and much more general problem is that people can never make absolute judgements about their own abilities. They can only make relative judgements, gauging the degree of success with which they meet the demands of tasks which they know others can accomplish, or by comparing their own performance directly with that of colleagues, spouses or acquaintances. In other words, people’s knowledge of their own abilities depends entirely on their degree of experience with the particular situations and tasks about which we question them. It also depends on the extent to which these tasks or situations can give them accurate feedback about
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their own levels of performance. Finally, even when accurate feedback is available, it depends on how accurately they can assess and remember it. Further postgraduate work in our laboratory has found that a crucial determinant of accurate self-prediction is the degree of specificity and familiarity of the particular task on which people are asked to predict their performance, and also the degree of precision and explicitness of the feedback that they obtain from it58. Elderly volunteers rated their ability at solving cryptic crossword clues and were then given a suitable objective test of this ability. As the volunteers in this study all claimed to be crossword enthusiasts, they would all have received frequent and unambiguous feedback about their performance. This was reflected by the fact that their selfratings were strongly (and highly significantly) correlated with their objective performance. It does, therefore, seem that when we probe their competence on very familiar tasks, older people can be very accurate judges of their own performance. Thus, if appropriate precautions are taken, subjective self-ratings can greatly contribute to good system design. There are however, further problems related to subjective evaluations given by older people. An example of this comes from further experiments carried out during the evaluation of the audio-description of television service, mentioned above21. As described, these experiments showed that objective performance significantly declined as the bit-rate reduced (9.4kbps to 6kbps), yet the volunteer’s subjective decisions about which bit-rates were clearest or were same/different were all found to be around the level of chance. This indicates that differences in speech quality which significantly affect objective intelligibility may, nevertheless, be subjectively imperceptible. These and other similar results show that while it may be useful to obtain subjective judgements, it is always also necessary to make objective tests. The converse it also true, because, for example, alterations in speech quality that do not affect objective intelligibility may, nevertheless, prove so subjectively irritating to some listeners that they are unacceptable in practice.
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Part Two Relating human factors to interface and interaction elements
Chapter
5
static elements
This section of the Style Guide addresses aspects of the interface between a human user and an interactive system. As with the first section, the division of the subject matter among discrete chapter headings is somewhat arbitrary. However, no clear-cut distiction is implied and any relevant connections between topics will be described within the discussion as appropriate. This chapter and the subsequent one have been distinguished along the lines of ‘static’ and ‘dynamic’ elements of the interface, respectively. In this context ‘static’ elements are those which relate most closely to the format of any individual presentation of multimedia information, whether this be a ‘stand-alone’ presentation of a single ‘screen’ of information, or part of a series of such ‘screens’ which form an interactive dialogue. Whereas, ‘dynamic’ elements are those which relate most closely to connecting those ‘screens’ together in a coherent and meaningful way. In somewhat simpler terms, it could be said that the former is primarily concerned with ‘spatial layout’ and the latter with ‘temporal layout’. One benefit of this separation is that it loosely parallels the distinction between the perceptual and cognitive human factors described in Chapters 1 and 2, respectively. That is to say, the constraints upon the static elements of an interface are generally due to the age-related limitations of the perceptual system, whilst the dynamic elements are generally constrained by attenuated cognitive processes. The bulk of the present chapter then, deals with visual aspects of the interface although attention will be paid to aural aspects too. The latter will also include a section on the presentation of speech, which although stretching the definition of ‘static’ outlined above, seems to fit more comfortably among the perception related issues than it would among the more interactive issues covered in the following chapter.
Visual Chapter 2 described some of the key changes in vision experienced by many older people. The following sections will relate these changes to the various elements involved in presenting visual information to users of interactive systems. Perhaps the most ubiquitous form of visual information is text, which will initially be addressed at
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the level of characters and words. This will be followed by a section covering the level of larger bodies of text and their layout on the screen. Subsequent sections will describe other elements of screen layout, such as icons, pointers and highlighting. Text
There is a large body of literature about the legibility of text on the printed page59. However, there is also evidence that very little of this can be validly applied to television/computer monitors because of the differences in resolution, such that a character on a page is a solid pattern with a clearly defined boundary, whereas a character on a monitor is composed of a matrix of pixels and so has a less well defined boundary60. There is a similar disjoint between findings from studies of coloured text. This is mainly due to the differences in producing colours with passive light (print) and active light (monitor). Thus, only work on text and colour produced by active light will be referred to here. A variety of research has examined the effects of different letter sizes. It is apparent that anywhere other than in an experimental setting, it is not the letter’s size per se that is important, rather it is the visual angle it subtends at the eye of the viewer (and as such will vary in relation to viewing distance, see Example E). The general recommendation for optimum legibility seems to be between 20 minutes of arc61 and 24 minutes of arc62. In addition, it has been found, that volunteers’ time to complete a variety of reading and search tasks was significantly increased as the visual angle of letters was decreased from 29 through 25, 17 and 13 minutes of arc (as a trade off between better performance and efficient screen use, they recommended 25 minutes of arc63). However, these figures are based on findings from a predominantly young population, suggesting that a somewhat larger minimum would be required for an elderly population. Bearing in mind that interactive services will mainly be accessed in the home environment there is little utility in trying to recommend an absolute minimum letter size as the visual angle subtended by any letter size depends ultimately on the distance of the viewer from the screen. Obviously, given the setting there is no way of controlling this variable. Also, it has been shown that it is virtually impossible to meaningfully describe average viewing distances of people in their homes for any group of people, as it is influenced enormously by many other factors and, thus, has a great deal of (mostly unexplained) variation64. Even if a useful average viewing distance did exist, this would ultimately be confounded by the variability in screen sizes. This study also showed that there is an almost equally wide variation in the lateral angle from which people view the screen with apparently few sitting directly in front of the screen (0°) and the average viewing angle they found was 23.3° (standard deviation 15.3°). It is interesting that so few view from 0° as this is the assumption made in most studies involving people viewing monitors and it is apparent that (regardless of letter height) a deviation from 0° will make letters effectively thinner (and 41
presumable less legible). In addition to this, various other factors have been indicated that can affect the visibility of a television screen, such as ambient light levels, glare from lights and the general quality of the screen in question, including its size, quality of contrast and the accuracy of the electron gun65, 66, 67 . Thus, the ‘ideal’ character size becomes a relative issue. For elderly viewers it could be said ‘the bigger the better’, however, there will be numerous constraints on this heuristic, not least of which is limited screen size, and the importance of having as much as possible of a coherent ‘message’ available on-screen at a given time.
Example E: The effective size of a character varies with viewing distance.
These schematic illustrations demonstrate how the image of a character projected to the retina diminishes in size with greater viewing distances. It should also be noted that, due to limited numbers of receptor cells, a reduction of size also means a reduction of resolution. (NB: Actual retinal images of readable characters are considerably smaller than those below.) For example, referring to the recommendations outlined in the main text above, 30 minutes of arc is equal to half of 1º. Relating this to the smallest retinal image shown below (approximately 4º of arc) gives a flavour of the importance of the clarity of characters.
A A
A
Regarding more qualitative aspects of texts, another issue at the level of characters is font design. It is reasonably well accepted that in general, ornate fonts should be avoided partly because they are more susceptible to degradation (both objectively and subjectively) and partly because they present less familiar letter and word contours68, making their perception relatively more difficult 42
(see Example F). Research into printed text has generally indicated that seriffed fonts (such as Times Roman presented here), tend to be more legible than sans serif fonts (such as Helvetica presented here) on the basis that the serifs enhance the termination of strokes in the letter making it more distinct particularly for small sizes of text59.
Example F: Examples of some of the font characteristics which can affect legibility.
Ornate fonts are more easily degraded and present less familiar word contours. Ornate fonts become particularly difficult at smaller sizes (especially with limitations of on-screen resolution.
The importance of familiar word contours becomEs aPparent in this example of ran omizeD font styles and upper and lower cAse ch racters. Less so on the printed page, ‘fat’ fonts tend to blend together on-screen.
Charactersplacedtooclosetogethercanalsomakewordsandthespacesbetweenmoredifficulttoidentify. Insufficient contrast with the background also causes difficulty. Patterned or pictorial backgrounds can interfere with character and word contours. Combinations of the above can multiply the negative impact on legibility (see below). Combinationsoftheabovecanmultiplythenegativeimpactonlegibility.
However, for screen presentations there is less of a consensus about this issue and it would seem (particularly at smaller sizes) that seriffed fonts are more likely to blur rather than enhance stroke terminations and the letter’s contour. This type of effect is likely to be increased for an elderly population who will tend to have reduced visual acuity. The potential benefits of sanserif fonts for on-screen presentation have recently been realised by the development of the Tiresias screenfont which has been rigorously evaluated by the RNIB and found to be of great utility to people with a variety of visual impairments, including the elderly69. This typeface has also been specifically developed to be ‘compatible with current screen generation technologies’, and as such ‘has been adopted by the UK Digital Television Group as the resident font for interactive television’. Thus, it is strongly recommended that the above reference is followed up and this resource is seriously considered by the developers of any interface involving text.
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Another factor that will affect the distinctiveness of text is the relationship between the text and its background. One aspect of this is the contrast of brightness or luminance. The uncertainties of screen quality and glare limit the effectiveness of any kind of minimum requirement set at source. In general though, the consensus seems to be for a luminance contrast of 2:1 or 50%65, 70. The ‘direction’ of this contrast has also been investigated. Some have found no significant differences between negative (light text on dark background) and positive (dark on light) polarities71, but where differences are found the tendency is for the positive polarity to be better72. Further support is offered for this option on the basis of uncertain screen quality in that imperfectly defined characters are more likely to be (perceptually) more blurred by their brightness68. This effect on the visual system will also make characters appear larger than they are, increasing the likelihood that they will run into each other. However, it is apparent that if character strokes are relatively thin, presentation in the positive polarity could mean that the relative perceptual enlargement of the bright background will make the characters less distinct. It is also worth noting that development of the Tiresias screenfont included equally legible versions in both, positive and negative polarities. In addition to simple luminance contrast, the prevalence of colour monitors has made colour contrast an important factor. Some studies have demonstrated that high levels of reading performance are possible with chromatic contrasts at equiluminance73. However, it is also indicated that performance with any colour combination will almost invariably be improved if the luminance contrast is increased (to around 50%). This suggests that the actual colours used are fairly irrelevant except with regard to subjective preference. It has further been found that subjective ratings of colour combinations showed a tendency toward preferences for desaturated combinations rather than saturated ones71. In addition, it was found that some desaturated combinations were felt to be more vivid than black/white (however, these combinations were presented in the context of luminance contrasts well above 50%). Further, preferences for colour combinations showed very broad variation which indicates notable individual differences, which in turn suggests the possibility of allowing the user to choose their own combinations. This suggestion should be treated with caution as this study found no clear relationship between ratings of subjective legibility and objective measures of performance. In addition, it has been demonstrated that ‘expert’ judgements of ‘good’ combinations are not reflected in people’s performance68. There is also evidence from various other cognitive domains that older people are particularly ‘disconnected’ in this regard (see limitations of questionnaire data, Chapter 4) and, thus, may not be the best judges of which colour combinations would be most suitable for them. Another issue of colour combinations for older people is the tendency for the lenses of older eyes to yellow which will filter whatever colours are presented to them and is, thus, likely to alter the perception of the colour combination6. Other types of ‘filter’ may have even more dramatic effects on the intended
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colour contrast, such as colour blindness which in its various forms affects around 5 to 10% of the population with a tendency for this proportion to increase beyond the age of around sixty years74. This may be related to the finding that the ability to discriminate hues decreases with age75. For any interactive television service there is also the fact that many people (particularly less well off elderly people) may still have monochrome televisions. Although the author does not know the actual extent of this, it has recently been indicated that 40% of the elderly population are effectively on the poverty line76. Such findings further emphasise the relative importance of maintaining a good luminance contrast between text and background. The relationship between text and background becomes further complicated by the availability of textured and photographic backgrounds. Little research seems to have been carried out which directly address this, however, studies (cited in68) have demonstrated a decrement in legibility when black text was presented against a white background ‘patterned’ with random black dots (ratio not given). This seems to be another manifestation of the kind of factors mentioned above which interferes with the distinctiveness of character boundaries and word contours (see Example F). It seems reasonable to extrapolate a similar negative effect for text presented against pictorial, photographic, video, or other ‘busy’ backgrounds, which could act as localised ‘noise’ against the characters and words. It is apparent that more research is needed to keep up with these kinds of graphical technologies. However, if these kinds of background are considered aesthetically important for a particular application, legibility would likely be improved by the use of localised backgrounds (eg ‘boxes’ or ‘strips’) in high luminance contrast to the text. It should be noted that the discussion above relates primarily to reading continuous text. Thus, the more ‘critical’ the information conveyed by the text, and the more complex or convoluted this ‘message’ is, then the more important it becomes to present the text with as much clarity as possible. This is because even a slight attenuation in clarity can have a ‘knock-on’ effect and detract from subsequent understanding (see Chapter 3). On the other hand, while the factors outlined above should always be considered to some extent, the necessity for ‘absolute clarity’ of text is somewhat diminished in the context of brief and simple statements. Thus, for more explicit and straightforward messages it is the more apparent issues of legibility per se that becomes the main consideration. Similarly, single words (eg headings and labels) need to be legible but will generally be less sensitive to the factors outlined above. However, other factors are involved in presenting single words, these will be dealt with in the Icons and logos section below. Screen layout
There are also a variety of literatures relating to the layout of text. This includes examination of differences between left, right and both sides justified
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text77, fixed versus variable character spacing78, full page versus two column layouts67 and the effects of chunking lines of text into semantic or syntactic units79 and other, similar formatting techniques80. However, the effects of such factors (where there are any) depend greatly upon other factors, such as content and the reader’s familiarity with it81, also the relative amounts of explicit and implied information82. The intentions and expectations of the reader (ie what they want to ‘get out of’ the text) will also affect optimal layout. That is to say, a passage of text will be approached differently if it is a fictional story, a news article or instructions for carrying out a task. Also, as has been mentioned above, virtually none of this work directly addresses the requirements of older people, so only a few relatively general considerations will be outlined here. Some of these considerations can be extrapolated from those at the level of characters. That is to say, sufficient space should be placed between lines of text so that adjacent lines do not interfere with the contours of the line being read. This issue is particularly important if information is to be presented in tabular form. It has been found that on-screen tables can be relatively difficult to scan, usually because too much information is condensed onto one screen83. This situation can be improved by ensuring that grid-lines (which are useful for orientation) are kept relatively fine and are presented in a distinct (and relatively subdued) colour to that of the content. Information ‘traditionally’ presented in tables (eg train times) can often be presented in more ‘userfriendly’ ways by capitalising on the interactivity of the system (more will be said of this in the following chapter). Another factor related to adequate spacing between lines of text is the ease with which a reader can proceed from the end of one line to the start of the next. It has been found that relatively small gaps between lines can disrupt this transition67. As with many of the aspects outlined above, no absolute minimum can be indicated as such studies which have addressed this issue suggest that the optimum gap depends on the length of the lines, the extent (expanded/condensed) and type (proportional/constant) of character spacing and whether or not the text is right-justified. Important elements of a particular text can be highlighted or emphasised (eg bold, distinct colour). However, these should be kept to a minimum and, unless absolutely necessary, only one ‘level’ of emphasis should be used. Also, such emphases as are used should be kept as consistent as possible throughout the text concerned (and beyond, so that the scheme [s] used can become familiar enough to be understood ‘automatically’). Texts that become too ‘busy’ in this way are very likely to distract rather than orient older readers. Issues related to the use of highlighting will be discussed further in the Highlights and pointers section below and in Chapter 6. In general, research into reading suggests that when space is at a premium text should be blocked into meaningful (and preferably succinct) ‘messages’68. If
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the message to be conveyed is beyond the capacity of a single screen then particular consideration should be given to connecting the messages on each screen. For example, the final sentence from one screen could be duplicated as the first one of the next, or a sentence summarising the previous screen could ‘introduce’ the next. Alternatively, each screen could be numbered (eg 1 to 4) and the reader given the ability to go back and forward as often as necessary. It may be tempting to sidestep these issues by presenting text in a scrolling window. However, this approach should only be adopted with extreme caution and can only be considered potentially viable if the user has control of both the speed and direction of scrolling. Beyond this, it has been found that young people with slight visual impairments need a significantly larger amount of scrolling text available at any given time (ie a larger window) than their normal seeing counterparts, to reach comparable levels of reading performance84. It seems reasonable to assume that the additional cognitive limitations of elderly people would mean the need for a larger window still. Again, these considerations become less problematic if the information is relatively succinct. However, it is known that for larger bodies of text (on the printed page) most readers (and particularly older ones) will often rapidly review words and sentences several lines prior to their current one in order to grasp inferences81. It is likely that scrolling text would make this activity difficult if not impossible. Such difficulty with reviewing previously read text may underlie the finding that given scrolling text, young volunteers demonstrated reading speeds around 35% slower than for equivalent static text85. Although slower reading speeds usually relate to improved (or maintained) comprehension, it was found that levels of understanding for scrolling text were still only about 85% of those for the static equivalent. Finally, the area of explicit, specific instructions (eg for system operation) is worth addressing again. The importance of giving elderly people clear and easy to understand instructions was discussed in Chapter 3 and a further aspect of this is relevant here. Studies have been carried out on the efficacy of additional textual instructions associated with television advertisements. These have shown that, although the wording of the instructions was carefully chosen by experts, around 35% of the volunteers demonstrated completely inaccurate comprehension of the message and that of those remaining, 45% demonstrated ‘partially’ inaccurate comprehension86. Further to this, it has been found that older people are prone to such miscomprehension87. Thus, the researchers involved in these studies strongly recommend that, rather than rely solely on experts with ‘inside knowledge’ of the topic in hand, the wording of such instructions should be agreed with groups of naive volunteers so as to minimise the possibility of miscomprehension. The danger of basing such instructions on ‘inside’ knowledge is that those on the ‘outside’ may well draw very different and unexpected inferences and conclusions from their reading of the text.
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It is apparent from the above paragraphs that the interdependence of so many elements of textual layout disallows a simplifying list of ‘dos and don’ts’. However, the overriding principle that emerges is that very careful consideration needs to be given to the information the text is intended to convey, its relation to any other elements of the on-screen display and the likely expectations, requirements and relevant knowledge of the reader. Beyond the format of on-screen text there are numerous other issues related to screen layout. Some of these issues will be addressed in the following sections of this chapter. Other aspects of screen layout are more related to the human factors of attention and working memory, these will be addressed in the relevant sections of the following chapter. Icons and logos
It is apparent that many of the factors relating to the legibility of text (particularly at the level of characters) will have similar effects with regard to the legibility of icons and logos. However, the fact that icons are discrete entities which represent their own meaning (function, etc) raises further considerations to ensure their usefulness for older people. The extent to which an icon represents its meaning is important for all novice users, regardless of age. For example, representations of a limited set of editing operations (eg delete) were used in a choice reaction study88. That is to say, following an initial training period, volunteers were presented with an on-screen written instruction which was followed by a set of representations, from which they had to choose the appropriate representation as quickly as possible. The types of representations involved were, meaningful icons, arbitrary icons and words. Perhaps, not surprisingly, they found that fewest errors (2.8%) were made selecting from sets of words (which simply duplicated the original instruction). Regarding the icons, the meaningful icons produced significantly fewer errors (3.9%) than the arbitrary ones (7.9%). In contrast to this, the words took longer to find (3.9sec) than both the meaningful icons (2.9sec) and the arbitrary ones (3.3sec). Perhaps even more relevant here is the finding that when one week later the volunteers were tested for recognition of the icons (the words were not included in this as it makes little sense to have a volunteer identify the word ‘delete’ as representing the delete operation), it was found that accuracy for the meaningful icons was very high in an absolute sense (97.1%) and in relation to that for the arbitrary ones (70.6%). A broadly similar finding was presented by a study which used a test of recall rather than recognition, with volunteers reproducing meaningful icons more accurately than meaningless ones89. It is also worth noting that the most accurately recalled characteristic of all the icons was shape (ie line pattern) rather than colour or location. This memorability aspect is particularly important for icons used in any service likely to be used only occasionally. The studies mentioned above generally employed young rather than old adults as volunteers. However the general finding for better memory for meaningful, rather than meaningless material is supported by more theoretically oriented research with young adults90 and older ones91. Further, it has been argued that this difference is exaggerated with advanced age, with memory for meaningful material showing
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relatively less decline than that for meaningless92. In simple terms, this is claimed to be due to the relatively richer semantic context related to meaningful material and that anything related semantically to an item is a potential memory cue. It was described in Chapter 3 that the memory performance of elderly volunteers tends to be improved with more or better cues (eg recognition ‘copy’ cues compared to cued or free recall). Thus, it would appear that icons which represent their meaning as clearly as possible are more likely to be initially understood by elderly novice users and are more likely to be remembered should they be encountered only occasionally. As was advocated for written instructions above, it is worth checking the meaningfulness of any proposed icons with a sample of naive volunteers who again may not share the same ‘inside knowledge’ as the designer. Depending on the context, it is also worth considering the provision of both pictorial and textual representations as there is some evidence that people tend to be either verbal or visual thinkers and have a preference for one or the other type of representation83. In some situations it may be more suitable to present icons and labels together, but in other situations it may be better to allow alternate routes to the same function. An example of the latter is common in many PC software packages such as word processors which often have iconic ‘toolbars’ and textual menus giving access to the same operations. However, beyond the needs of the user per se, decisions about icons and/or text may also be suggested by the nature of the task the interface is being designed for. Thus, icons (and logos) if carefully chosen (or designed) can be useful elements of an on-screen display, although it is very important that they meaningfully represent the associated ‘object’ or action. This means it is also important to ensure that each of a set of icons on a particular screen (or involved in a particular task which may span more than one screen) are as distinct from each other as possible. Other possibilities have been suggested for enhancing the clarity and meaningfulness of icons83. For example, giving an icon a 3D appearance (with suitable shading and/or offset shadow) is claimed to enhance clarity. However, it is important to ensure that the (pseudo) light source is consistent throughout, otherwise the result is more likely to be a loss in clarity rather than a gain. Another possibility is the use of animation, which can both enhance the meaningfulness of an icon and distinguish it from other, potentially similar ones. These possibilities should be approached with extreme caution, as there does not appear to have been any research to establish the benefits of these techniques with regard to elderly people. A method that should help anyone who is designing icons (or an interface which uses them, or indeed, text) has been used with substantial success in the redesign of Canadian traffic signs. This method has been shown to generalise to on-screen icons10, and it involves designing the icons (screen layout, etc) while viewing through a ‘low-pass’ visual filter (described as ‘strong positive-sphere lenses’). In the context of traffic signs, this approach produced symbolic signs with visibility distances 50% greater than the previous ‘standard’ ones. Such an approach should at least ensure that the clarity of icons is ‘in the right ballpark’ before they are checked with a representative user group.
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Highlights and pointers
Some of the issues relating to the use of highlighting were touched upon in the earlier section on text. Obviously the use of highlighting can relate to other aspects of screen presentations. In this broader context, a useful distinction can be made between two (functional) aspects of highlighting. That is, highlighting can be used to draw the users’ attention toward a particular area of the screen (exemplified by the type indicated in the section on text above), although highlighting can also be used to indicate ‘active’ screen elements. Some aspects of both these forms of highlighting will be discussed here. However, other aspects function in a more dynamic way and will thus be addressed in the following chapter. Analogous to the highlighting of text, more graphically oriented screens can use highlighting to draw users’ attention to an important area of the screen. However, given the pictorial nature of such screens, highlights such as ‘bold’ and ‘underline’ are much less likely to be useful. Of more use in this context is ‘active’ highlighting. One example of this is movement such as: a small movement up/down or left /right or, a ‘throbbing’ icon (ie expanding and contracting in size) or some other type of animation. Another approach is to use changes in colour and/or luminance (ie ‘flashing’ or ‘blinking’). It is worth noting that these forms of highlighting are less suitable for text as they are likely to have a negative impact on legibility. It is just as important, however, to minimise the number of highlighted areas on a single screen to avoid confusion (and the possibility of visual discomfort).
As mentioned above, one form of highlighting is to indicate ‘active’ elements of a screen display. To some extent the definition of an ‘active’ element depends upon the type of task being carried out (eg ‘form fill-in’ transaction, information search, etc) and on the input options available to the user. Regarding the former of these, issues relating to interaction ‘tasks’ contained within a single screen will be discussed below and some of the points made will be expanded upon and related to interaction ‘tasks’ spanning more screens in the following chapter. The issues of ‘active’ elements as dependent upon input options will be indicated as appropriate and also related to the use of ‘pointers’ and other forms of ‘cursor’. Some types of task involving a single screen are very basic, such as ‘selecting’ a single item from a set of options. In general, the role of highlighting for such tasks depends upon whether ‘selection’ is a one- or two-step process (this depends to some extent on the type of control device used, see below). Onestep selection, most commonly involves a numbered list of options any of which can be selected with the relevant numbered key (see Example G). Thus, the option is ‘selected’ and ‘activated’ simultaneously. In this situation, ‘highlighting’ can be useful as a form of feedback to the user, such that the list item selected might flash (or similar) briefly before the list is replaced by the next on-screen display (more will be said on the importance of this in subsequent chapters).
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Example G: Various keypad arrays commonly used on ‘standard’ remote control handsets.
Numerical
1
2
3
4
5
6
7
8
9
Arrows
Video/Teletext
3 3
4
4 4
3
g
4|
||
G
Y
B
|
Select
R
Select
Note that the numerical keypad pictured represents a ‘telephone’ layout93 and seems the most common layout for TV handsets. Perhaps the next most common is the ‘adding machine’ layout (ie with keys in ascending order, left to right and bottom to top). However, other layouts also exist and can cause confusion with older people if it is not ‘what they are used to.’ Also, the bottom row of the Video/Teletext panel (ie ‘fastext’ keys) is normally presented in their relevant colours (here represented by initials: Red, Green, Yellow and Blue).
Two-step selection separates ‘selection’ and ‘activation’, by requiring discrete button presses. In this situation, two distinct forms of ‘highlighting’ can be helpful to the user. First, one type of highlight can indicate the currently selected item. This may initially appear on any item, given an exclusive relationship with a particular key, for example, a numbered list and numerical keypad or, for small sets of options, the ‘fastext’ keys. Alternatively, an item may be initially highlighted ‘by default’, from which the highlight can be moved ‘step-by-step’ to other items in a relative relation to the keys. A common example of this is an ‘arrow keypad’, although systems evaluated by the present author have occasionally utilised certain of the video function keys (eg using ‘search’ forward/backward keys in relation to next/previous item). This type of highlight makes it clear to the user which option is ‘ready’ to be activated. Indication that the selected option has been ‘activated’ by another key press can then be given by a different form of highlight. An example of this may be that the ‘selected’ item is distinguished by a different coloured, localised background, then on ‘activation’ of that selection, this background could blink briefly before the subsequent screen appears. Suitably highlighted two-step item selection is beneficial to users as it limits confusion by making it clear to them not only which option is to be selected but also that it has been selected. Evaluations carried out by the present author suggest that older people prefer the two-step selection process as it limits the extent of problems due to inadvertent errors. Such errors are increasingly likely for older people due to difficulties in shifting vision and attention
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between handset and screen and these issues will be discussed in more detail in subsequent chapters. In addition to straightforward item selection, there are many, more complicated interaction tasks which can be carried out on a single screen. In these situations various forms of highlighting can be beneficial to the user. However, successful implementation of them can be quite demanding of the designer. Ultimately the ‘correct’ use of highlighting depends entirely upon the specific nature of the interaction task and its goal(s). Therefore, by necessity the following discussion will only address general issues and principles, however, some illustrative examples will also be given. Much of the following discussion will describe ways of using highlighting to ‘guide’ the user through the steps of an interaction. However, it should not be forgotten that these forms of guidance will not replace the need for explicit instructions, but can be very useful as a subsequent ‘aide-mémoire’, particularly for older, novice and/or occasional users. While highlighting is useful for guiding users through a task, it may often be worth considering constraining the stages of a task in a more absolute way so as to minimise or completely avoid errors. One approach to this is to ‘force’ the user through the appropriate sequence of operations by imposing a temporal order of active and inactive fields. Approaches of this sort also introduce the option of ‘lowlighting’. Examples of this can often be seen in dialogue boxes of various PC software applications, wherein available options will appear as normal but currently unavailable options will be ‘greyed out’. This ‘greying out’ means the option can be seen (and so is potentially available in other circumstances) but is distinguished from the other items by its ‘lowlighting’. An example of an interactive task that would likely have benefited from ‘highlighting’, ‘lowlighting’ and a constrained order of operations is given in Example H and will be discussed further below. Most of the difficulties the elderly volunteers had with this task could have been eliminated if the interface had given them more guidance. The following discussion will address the main difficulties encountered and describe possible solutions.
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Example H: An illustrative example of an interaction task which may have benefited from more considered use of ‘highlighting’, ‘lowlighting’ and constraint of operations.
This illustration represents the screen display for the interaction described below, apart from the lack of colour and a slight variation in the fonts used, it faithfully reproduces the interface used. The volunteers used a remote control handset containing all the keypad arrays illustrated in Example G.
Car Hire Group
red
Collect Drop off Days Quote
: Saloon : London : London :1 £25.00
press SELECT to finish
One of the services available in the simulated interactive system mentioned previously, allowed users to obtain a quote for hiring a car. Elderly volunteers involved in the evaluation were given task instructions which specified the type of car (‘Group’), the collection and drop off locations and the number of days required and they were asked to write down how much this would cost (‘Quote’). In order to get the appropriate quote the user must select the correct options from each of the four ‘fields’ (ie ‘Group’, ‘Collect’, etc.). To achieve this the user must first have a concept of ‘fields’ and realise that this screen is an instance of this convention. Given this ‘baseline’ understanding, the user must then identify which is the ‘active’ field, how to move between ‘fields’ and how to select a particular option within a chosen ‘field’. In this instance, the active field is indicated by a red ‘cursor’ adjacent to the field’s ‘window’. To proceed, the user must recognise that the red ‘cursor’ means that ‘Group’ is the (default) active field and that to select an item in this field the left/right directional arrows on the handset must be used to scroll through the options (Saloon, etc), until the desired one appears in the ‘window’. Once this has been achieved the user must then use the up/down directional arrows on the handset to select another field and then use the left/right arrows to select an option, and so on until all fields display the desired options at which point the ‘Quote’ field will show the relevant figure for that set of options (note that the figure in the ‘Quote’ field is constantly updated as different options are selected). Many of these volunteers had difficulty even getting started with this task and hardly any completed it successfully.
The ‘cursor’ used on this screen caused two distinct types of difficulty. First, being the only coloured object on the screen it stands out more than any other item and given no other instructions as to how to proceed (including the fact that this was effectively a ‘place marker’), it seemed to be considered by some as a ‘good starting point’. About 25% of the volunteers tried to relate this starting point to the keys on the handset and focused on an ‘obvious’ mapping. That is, the handset contained a red, square key which maps very directly to the red, square entity on the screen and 53
thus they assumed that pressing this key ought to ‘do something’. Given the lack of any other information this direct mapping seems a reasonable assumption, but it failed to produce any response from the system. A similar number of volunteers simply ‘got stuck’ at the outset of this task and needed varying amounts of prompting from the experimenter before they could proceed. The others felt confident enough to proceed on a ‘trial and error’ basis. However, many of these soon lost confidence and also needed prompting from the experimenter. A few did realise the role of the arrow keys although some misread or misinterpreted ‘press Select to finish’ and used this button to ‘input’ their first selection, and becoming confused when they were taken back to the previous screen. The others did manage to ‘complete’ the task, although only three managed to record the correct quote. So, although around 10% successfully completed this task, approximately 60% ‘gave up’ in frustration, and perhaps worse still, the remaining 30% thought they had completed the task correctly but had not. It is apparent that many of the difficulties these elderly volunteers experienced could have been eliminated with a few lines of relatively simple instructions on how this interface operated, or the option of an animated preview example similar to the ‘answer wizards’ increasingly common in PC applications. However, even ‘ideal’ instructions would likely have only a limited impact on the ultimate accuracy of those volunteers who thought they got it right. That is to say, the errors these people made were mainly due to inadvertent key presses. For example, inadvertently hitting a left/right key (ie changing their previous selection) while hitting an up/down key in order to proceed to the next ‘field’. Part of this problem is the design of the handset and this issue will be addressed in Chapter 7. However, regardless of the particular handset used, much of this difficulty could be removed by constraining the task so that the user deals only with a single step at a time. For example, the initial screen presentation could contain an instruction to press a certain key to start. Once this has been done the first field could become active and be indicated as such with some form of highlight. A possibility for this might be a flashing ‘box’ around this field or it may be sufficient to ‘lowlight’ the other fields. Also, the original instructions could be replaced (with suitable highlighting to indicate this) with ones indicating the left/right arrow keys to scroll through the options and the Select key to choose the one desired. When an option has been selected the highlight can move to the next field and so on until all required fields have been selected. Another possibility would be that when the ‘start’ key has been pressed, the first field is highlighted and flashing arrows appear either side while the available options automatically scroll past a ‘window’ to suggest the underlying selection method (it is worth noting that the original interface did not use an apparent ‘window’, also, the text did not scroll into view, which may have made the use of the left/right arrow keys more meaningful). Once all the required options have been selected, then the quote could appear. As the goal of this interaction task is to get a quote for a specific set of options, it makes little sense to show the Quote figure being constantly updated in respect of sets of options not required by the user. Several of the elderly volunteers experienced a variety of types of confusion because their attention was drawn to this area of the screen by the ‘flickering’ of the numbers changing. In general, the basis for this confusion can be characterised as ‘Why are things changing down there when I am trying to change things up here’. Confusions like this are likely to be drastically
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reduced if presentation of irrelevant information is avoided and if the users’ attention is focused on one screen location at a time. Any similar interaction task which has the aim of producing a goal based on a set of specified criteria will benefit the user if the goal is presented along with confirmation of those criteria (and would have undoubtedly reduced the number of elderly volunteers who erroneously thought they had completed the task successfully). In the context of the original screen layout it may have been beneficial if, on completion, the quote had appeared in a highlighted fashion and subsequently each of the selected fields blinked briefly in succession so that the users’ attention is drawn to each as a ‘reminder’ to check for errors. Another possibility would be for a new and distinct screen to appear (which would help to suggest completion of the task) which presents confirmation of the criteria in a more personally engaging way. For example, the screen heading could be ‘Your quote’ which could be followed by text along the lines of: ‘To hire a Saloon car, collected from our London branch and dropped off at our London branch, for a period of One day will cost £25’. Providing confirmation of details like this is a useful ‘safety net’ for the user to catch inadvertent errors before it is ‘too late’. Such errors are likely even if the interaction is ‘perfectly’ designed as the user may experience any amount of distractions unrelated to the interaction per se. Also, assuring error free interactions become crucial where the interaction involves a financial transaction. That is to say, consider the different implications (not only for the user but also for the service provider) of an error occurring when a user simply wants a quote for hiring a car and when a user is actually booking the hire of a car. Given that errors are virtually inevitable and assuming that the best efforts have been made to ensure that the user can become aware of such errors as they have made, the next important step is to ensure that corrections can be made in as straightforward and efficient a manner as possible. In some circumstances it may be sufficient to provide a ‘cancel’ option with the confirmation message, followed by ‘exit’ (to leave the current service) and/or ‘return to start’ options. However, this kind of approach is only viable if relatively few criteria need to be specified. That is to say, the ‘car hire’ interaction requires specification of only four criteria. Yet it is likely that the user would find it markedly less preferable to ‘start from scratch’ because of one error than to simply correct that error. The magnitude of this difference in preferences would likely increase with the number of criteria to be specified. An example of a service requiring more criteria also comes from the evaluation of the simulated interactive system outlined above. This service allowed users to book cinema tickets in advance. In this case, selection of the criteria was done in a more step-by-step/screen-by-screen manner than was the car hire quote. To achieve the goal of this interaction the following selections were required. First, the desired film had to be selected from a list of 12. Then, the required day was selected from (mostly) the next 14 days. Following this, the time of the screening was selected from (up to) four options. The number of seats required was then specified and finally, the position of the chosen seats could be specified on a plan of the available seats (see Example I).
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Example I: Booking cinema tickets: the importance of easy error correction.
Cambridge Cinema Please select your seat:
SCREEN
Key:
= blue
= red
= grey
Although this interaction task required specification of only one more option than for the car hire quote, the selection procedure was notably more demanding of the user. That is, the film was selected from a numbered list using the numerical keypad (and ‘Select’). The day and time were selected using the arrow keys (and ‘Select’). The number of seats required was entered as a numerical value (numerical keypad without ‘Select’) and, following this, the user was presented with the seating plan illustrated above (note that this is not to scale and the matrix of seats in the on-screen plan was 20 by 9 rather than 13 by 5). Regarding the key, the blue squares are ‘your’ seats (the task required the volunteers to ‘Book three seats for....’), the red squares are seats already booked and the grey squares are available seats. The block of ‘your’ seats could then be positioned using the arrow keys, followed by the ‘Select’ key (though no instructions indicated this). After this final key was pressed, a screen appeared telling the user ‘Your tickets are ready for collection at the box office’. This interaction gave no confirmation of what had been booked, allowing inadvertent errors to go unnoticed. Further, from the first selection of a film, to the final positioning of the seats, there was no opportunity to either ‘retreat’ one step or to cancel and start again from the beginning. The only errors that could be amended were those that could be spotted (and changed) prior to pressing the ‘Select’ key. It seems reasonable to accept that the user would be much better served in an interaction of this sort, if it were possible, to retreat through the steps and amend or recap on their input during the interaction; to receive a detailed confirmation at the end of the interaction and to make individual changes to criteria ‘directly’ via the confirmation screen. The ability to retreat through stages is important, not only to limit the frustration from inadvertent errors which are noticed ‘too late’ (eg just at the moment the ‘Select’ key is pressed), but also to allow the user to alter criteria on the basis of information gained during the interaction. An example from the cinema booking context might be of users who have selected the film they want, the day they want to see it and when selecting the screening time, discover that their desired time is fully booked. While some people may simply select a different time, some may prefer to stay with that time but on a different day. A similar scenario would be a family of four or five getting successfully to the stage of positioning their seats but finding that while there are sufficient seats available, there is not a big enough row of adjacent seats for their group. Again for some groups, sitting separately may be acceptable but for others 56
sitting together is more of a priority and they may rather prefer to change the time, the date or even the film. The importance of allowing such ‘back tracking’ is somewhat diminished if the user is aware that there will be a final confirmation screen that will allow them to make similar changes if necessary. One approach to this would be that, assuming the cinema interaction concluded with a confirmation message similar to that for the car hire task, that the (highlighted) criteria could be scrolled through and when one is selected, the user could be presented with a ‘drop down’ menu presenting the other selectable options. Whether just one change is made or a whole sequence (depending on the priorities of the individual user and how well they are catered to at the particular time of the interaction) the user can then complete the transaction by selecting an option that clearly indicates this function. It is apparent that interactions contained within a single screen and those spanning across more screens have different strengths and weaknesses. That is, presenting all the information on a single screen has the potential to ease the demands on the user’s memory. However, a relatively high number of criteria and the possible need for explicit instructions increase the likelihood of the screen becoming too ‘busy’ and thus potentially confusing for the user. On the other hand, separating the task into a sequence of screens reduces the likelihood of over-filled screens and will generally be beneficial for (particularly older) users as they only have to deal with one operation at a time. This latter approach does, however, run the risk of over-taxing an elderly user's memory (ie which steps have and have not been completed and which criteria were specified in those steps). Yet, in general, the extra screen space made available by a sequential approach allows more room to ameliorate this problem by providing reminders and other forms of guidance for the user. In contrast, it will often be relatively more problematic to provide adequate instructions while avoiding a presentation that is ‘too busy’ when the task is confined to just one screen. Presenting interactions on sequences of screens does raise various issues related to the disjoint between successive screens and ways of assisting the user across them. These topics will be discussed in more detail in the following chapter.
The discussion above covered highlighting and the selection of options in the context of indicating a single item (ie numbered lists) or ‘jumping’ between discrete items (arrow keys). However, there are also interactive systems which adopt a presentation style involving ‘free ranging’ on-screen pointers. In addition to those outlined above, the use of pointers raises other issues related to ‘highlighting’ in its broadest sense, and these will be discussed below. It is also apparent that the kinds of ‘standard’ keypad handset mentioned so far (including those with arrow keys) are generally not amenable to controlling such a pointer, however, Chapter 8 will discuss a wide range of possible control devices and their use by elderly people. Perhaps the most important aspect of an on-screen pointer for older people is that it is clearly visible. The first step towards ensuring this is to consider the size of the pointer. In a sense (as with text) it could be said ‘the bigger the better’, although generally, the larger the pointer the greater the chance that it could obscure important elements of the presentation. As with many of the issues addressed above, guidance on this can be provided by careful
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consideration of the nature of the particular interactive task being designed. If use of a pointer is a major element of an interactive service it may be worth considering giving the user the ability to customise the pointer according to their own preferences/requirements. Allowing customisation however, should not be considered an ‘easy option’ mainly because users are unlikely to have adequate knowledge of the presentation styles and layouts used throughout the available services, to judge the potential impacts of their choice. A simple example of this might be that a person chooses a blue pointer because they like the colour, only to find that a service they later want to use employs a blue background. This kind of problem may be limited if the customisation option is always available, although it may become frustrating for the user if they constantly need to change their options to suit local presentation styles. Thus, careful consideration is also needed to decide which set of options should be made available to the user is this way. Perhaps the most useful customisation parameter for older people would be the size of the pointer. It seems likely that most needs would be met by providing a small set of sizes within reasonable limits. For example, Windows 95 provides three size options of ‘Standard’, ‘Large’ and ‘Extra Large’ (reproduced approximately to scale in Example J, 1). The use of an arrow design as an on-screen representation is very widespread. However, it is worth pointing out that several of the system evaluations carried out by the present author have provided strong (albeit incidental) anecdotal evidence that many elderly people experience a certain amount of confusion due to their interpretation of this representation. That is to say, those who are familiar with this convention have implicitly learned that with this representation the screen location being indicated is that which is at the point of the arrow. However, for those not so familiar with this convention (ie many older people) this interpretation is by no means intuitive. Rather, the arrow is more likely to be interpreted in terms of its directional connotation of indicating the position of something at a different location, which in general terms is a far more common use of arrow symbols. This ‘misinterpretation’ combined with general uncertainty about other aspects of an interactive task caused several elderly volunteers enough confusion that it seems likely that, had they not received encouragement and prompts from the experimenter, they would have given up. During debriefing sessions, many of the elderly volunteers suggested other representations which they felt would make more sense as something that needs to be placed on the target (see Example J, 2 and 3).
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Example J: Alternative on-screen pointer options.
It is very common for free moving, on-screen cursors used in interactive services to be presented as arrow style ‘pointers’. It is likely that this has been adopted as a convention from ‘common practice’ in the personal computing environment. 1) Standard
Large
Extra Large
However, depending upon the situation it may often be worth considering other forms of representation, such as ‘Cross-hairs’ 2)
Or possibly, ‘Bomb-sights’ (these latter two are from sketches made by some of our elderly volunteers). 3)
Further to this, careful consideration of the design of a ‘pointer’ in light of knowledge about all of the on-screen environments it will operate in, can also limit the extent to which its ‘size’ relates to the amount of screen obscured. It seems apparent that modern graphical techniques open up an entirely new range of possibilities in this regard. However, virtually no human factor research has been carried out into the possible benefits such recent developments may provide for people with poorer than average vision. Thus, the importance of appropriate user testing of on-screen ‘pointers’ (as with most of the other elements of screen content discussed previously in this chapter) cannot be emphasised enough. Despite this paucity of data, some speculative, though potentially useful, approaches will be outlined below. The assertion that ‘larger’ pointers obscure more screen area, rests entirely on the premise that the pointer is entirely opaque. Given current graphical technology, this need not be the case. That is, it should be feasible to create designs (along similar lines to those depicted above) that are effectively line drawings, but with the lines made to contrast with the background as distinctly as possible. For example, the lines could consist of two adjoined bands of colour which represent high levels of (luminance and/or colour) contrast with each other. Thus, if local changes in the background mean that one band tends to ‘blend in’ then there will be a good likelihood that the other band will remain distinct. Another possibility might be to programme the on-screen representation with a ‘smart’ colour palette, such that any section of the line
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will appear in high (colour and/or luminance) contrast to the background immediately adjacent to it (‘reverse video’). Assuming the technical feasibility of an on-screen pointer which can respond to various aspects of the background suggests other possibilities of making the pointer easier to use. One important area regarding elderly (and novice) users is ensuring that they know when the pointer is on a target item. One approach to this (as mentioned above) is to highlight the selected item itself (or its immediate background, etc). Yet there may be additional benefits by highlighting this event with some change in the characteristics of the pointer. Example K illustrates a simple, monochrome scenario using changes to both the target item and the pointer. There would also appear to be scope for approaches involving animation and quasi-3D effects.
Example K: Various elements can be altered to make it clear when a pointer is on a target item.
The pointer approaching the target item is shown in 1 and 2. When the pointer is in suitably close proximity a highlight appears round the target item indicating it is ‘available’ (3). As soon as the pointer is within the target area, certain of its characteristics change (adding to the ‘highlight’ effect) and it becomes ‘centred’ round the target (4) and remains stable as long as the ‘pointer’ is within the target area. This allows a greater amount of tolerance (and a minimum of distraction), should the pointer be inadvertently moved slightly while the user tries to press the ‘select’ key. 1
Option
2
3
Option
Option
4 OPTION
Separate but related highlighting of foreground and background allows a distinction of the information to the user about when the pointer is on the target, and about what the target ‘has to offer’. In a simple sense this may be the difference between the target being ‘available’ (pointer highlighted and background highlighted) and it being ‘not available’ (pointer highlighted but background not highlighted [or possibly ‘lowlighted’]). Beyond this, there could be occasions when ‘available’ items could be distinguished on the basis of different ‘functions’. For example, an on-screen television listing service could indicate the availability of a written preview (eg red background) or of a video excerpt (eg blue background) or both (eg alternate red/blue ‘flashing’ background). Such 60
differentiation along a single dimension (ie colour) is obviously limited, yet this scope can be increased (within realistic limits) by adding other dimensions to the changes involved in the highlight. One possibility would be for the highlight to include symbols adjacent to the target (see Example L) which can themselves be ‘selected’ by the pointer.
Example L: The ‘highlighting’ of a target item could include symbols denoting different ‘functions’.
Including ‘coded’ symbols as part of a highlighting scheme should be based upon careful consideration of the whole service, the interaction tasks involved and their layout. The examples below show symbols distinguished by colour and shape (1 and 2 respectively). However, it should be borne in mind that arbitrary coding into colour or shape requires that the user ‘learn’ these codes. Thus, even though a scheme may appear to the designer to be very straightforward it will be necessary to provide explicit instructions. In part this is because (as mentioned above) the user is unlikely to have a similar level of tacit knowledge about the system as the designer and, thus, the former may not grasp what the latter sees as ‘obvious’. Also, it may well be the case that similar but conflicting codes are used in other services involved in the same system. While from a human factor point of view it would be desirable for such elements to be standardised across all the services in any interactive system, it is likely that achieving this in practice would prove problematic. Another approach might be to use meaningful icons as the associated symbols (3 below uses loose analogies, relating a ‘monitor’ icon with a video excerpt and a ‘document’ icon for a written preview). 1)
Option
2)
Option
3)
Option
Another potential benefit of a free moving pointer is that it can be used more readily (than the other indirect methods of ‘cursor control’) with more graphically oriented presentations. Wherein items, rather than being presented as discrete items in ordered lists, can be ‘hot spots’ which are ‘embedded’ in a pictorial scene. These ‘hot spots’ can indicate themselves as such when pointed at in ways analogous to those described above. However, relatively greater care is needed in designing ‘highlighting’ schemes in the relatively more distracting context of graphical and/or pictorial screen presentations. For example, the general visual ‘richness’ of such presentations tends to emphasise the use of ‘lowlighting’, such that if the background is colourful, items highlighted with colour will be relatively less distinct. Finally, the concept of a ‘software magnifier’ seems to have great potential as a ‘highlight’ element94. The magnifier was originally recommended for older people to use when browsing through on-screen displays (and depending on the type of service being developed this could be well worth considering).
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However, in addition to its use as a text browser, this idea would seem to offer benefits if used in combination with some of the approaches to highlighting outlined above. For example, the approach depicted in Example K could include an element of magnification, enlarging the ‘active’ target area and allowing greater tolerance of inadvertent movement of the pointer. Alternatively, the pointer could be centralised within a magnified area (like that used for browsing) ensuring that all users can see all items on the screen accurately.
Aural Chapter 2 described the general changes older people experience with their hearing ability. The following sections will relate the effects of these changes to the use of sound in interactive services. Audio prompts and ‘earcons’
In the context of the visual highlighting schemes outlined above, the additional use of sound to indicate ‘events’ has potential to benefit older users. However, changes in older people’s hearing ability means that great care is needed in the design and implementation of such audio prompts (or ‘highlights’). As a general principle, pure tones should be avoided, particularly ones from higher frequencies (ie 4kHz and above)95. If a ‘tone’ is deemed most suitable for a particular purpose then it should be designed to be ‘richer’ than a pure tone, so that there is a lower chance of it being entirely ‘masked’ by incidental noise. An example of this comes from studies of older people working with interactive systems in the work place, where the recommendation is for warning sounds to be between 1 and 2kHz and that the sound should have reverberation in ‘emergency situations’ on the basis that it adds a physical sensation of vibration and makes the sound more complex, making it more robust regarding its detection96. An example of the use of high frequency sound comes from a system evaluation involving elderly users, mentioned above. The system in question employed a series of consistently laid out screens which allowed the user to navigate to and between the various (and somewhat less consistent) services. Having ‘logged on’ to the system the user was presented with a ‘home’ screen, from which selection of an option took the user to the next level of a branching hierarchy toward the desired service. Following each selection, the current screen would ‘scroll away’ (bottom to top) to reveal the next screen. This screen transition was accompanied by a ‘page turning’ sound effect (ie ‘wshshsh’). Subsequent questionnaire responses indicated that many of the volunteers noticed this sound effect and found it useful (by indicating a screen change even if they were looking at the handset as the change occurred). However, it was also found that of the older volunteers (aged 70 to 80 years)
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about half were unaware that the sound had occurred. It is highly likely that this is a particularly conservative finding in relation to the ‘real world’. That is, the volunteers involved tend to represent the more able end of their age group (on the basis of their regular visits to participate in research) and the evaluation was carried out in a quiet room devoid of any distractions. Thus, given an ‘average’ elderly person in an ‘average’ living room, it is likely that a much higher percentage would miss this potentially useful audio prompt. Another difficulty related to using audio prompts (and any other sounds which occur ‘automatically’ and for only a short duration) is setting an appropriate volume level. That is to say, it would need to be quite loud in order to be heard by most people but on the other hand if it is too loud many other people may be ‘startled’ by it or even find it painful. This difficulty can be somewhat limited if the sound is given a relatively longer duration. Another approach to producing sounds ‘richer’ than pure tones come from the development of ‘Earcons’97. Earcons, in this particular sense are synthetic sounds (‘tunes’) constructed using ‘structured combinations of notes’. Thus, differing earcons are distinguished on the basis of ‘rhythm, pitch, timbre, scale and volume’. This allows the potential to generate a wide range of different sounds, and development of such sets of earcons have been used with some success in simulated work tasks. However, such success has followed significant amounts of training with the set of earcons concerned. This training is required because ultimately these sounds are abstract and as such can only be mapped arbitrarily to a particular function. Although relatively small sets of earcons could reasonably be developed for particular interactive services (in which case the above reference and related articles would be strongly recommended), their use would always require suitable instructions and examples to inform the user of their role. A related though distinct concept refers to ‘auditory icons’98. Auditory icons can be distinguished from earcons on the basis that they are generally made from ‘natural’ sounds. The strength of this approach is the possibility of the sound relating to an ‘action’ in a more meaningful way (eg the ‘page turning’ sound mentioned above). However, there is also the limitation that relatively few of the ‘actions’ in an interactive service will lend themselves to being represented by a sound. Another possibility would be ‘spoken labels’ whereby an item when selected could have its name spoken to enhance the visual highlighting of this event. Such ‘spoken labels’ may be useful in a variety of situations, however, if they are presented as isolated words it is vital that they are very clearly articulated and any other forms of degradation avoided if the words are to be heard by older users. Perception of such spoken words will be aided if they coincide with a written version of the same word (such as the item labels mentioned above) on the basis of bi-modal augmentation. Another possibility (if appropriate to the task and its layout) would be the simultaneous presentation of a ‘talking head’ (or possibly, mouth) to aid perception with lip reading99. The following section will address some of the particular difficulties older people have in listening to speech but it is worth bearing in mind that all of these will apply in even greater measure to words spoken in isolation.
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Speech and ‘noise’
The discussion in Chapter 2 indicated that any alteration (degradation, addition of noise) to even the most well articulated speech is very likely to cause elderly people relatively greater difficulty (compared to younger people) hearing and understanding it. Hence, a simple principle in this regard is to ensure that no other sounds are presented at the same time as speech. For example, it might be decided to add some background ‘mood’ music for aesthetic reasons. However, even if the music is set at what the designer considers to be a suitably low level, it will very likely interfere with older people’s ability to hear the speech. In the context of television broadcasts, this aspect of background music is the focus of an increasing number of complaints from older viewers. If however, the presentation of simultaneous music is considered important then rigorous user testing with an appropriate sample of volunteers would be necessary. At the very least, the user should be allowed the ability to remove the music if required. Thus, if ‘clear’ speech has been recorded for presentation then it should be presented in ‘clear’ with no other audio. Ensuring that the initial recording of speech is ‘clear’ is also very important for older listeners. This refers to both extraneous background noise and alteration of the original spoken message. That is to say, all efforts should be made to avoid any other noise being recorded with the speech. Another example of this comes from a much complained about aspect of television programmes. A common scenario would be a reporter giving an outside broadcast as part of a news bulletin and the message is recorded beside a busy city street, so that traffic noise is recorded along with the speech. As previously mentioned any noise competing with speech is disproportionately detrimental to older people and should thus be avoided where at all possible. At the time of writing this, the present author is involved in the initial stages of a research project co-ordinated by the ITC with the aim of developing processes which, given such ‘noisy’ recordings, will reduce/eliminate the level of noise and/or enhance the speech itself. It is hoped that the results will benefit older and deafer viewers, although it is apparent that the need for these processes is dramatically reduced if initial recordings of speech exclude other noise. The other main aspect that can make speech difficult for older people to hear is if the original ‘natural’ speech wave is distorted in any way. As described in Chapter 2, processes such as frequency band limitation, peak clipping and reduced information transmission rates can cause older listeners difficulty. Often these degradations are imposed by limitations of the technology employed (ie commercial/economic constraints such as self-imposed limits on ‘storage space’ or ‘bandwidth’). If such factors should require some compromise in the quality of recorded speech, several options are possible. One would be to produce the best quality possible and test it with elderly volunteers (preferably in comparison to ‘hi-fi’ speech). Should such tests prove positive then it would be reasonable to proceed. On the other hand, if there is
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any indication of difficulty, then other approaches should be followed. This is on the grounds that the actual service will operate in people’s living rooms where it will generally be inevitable for other sources of noise to interfere and further degrade the clarity of the speech and be likely to make ‘slight’ difficulties (in the laboratory) into significant ones. Another approach (mentioned above) would be to show the speaker’s face (although this would likely place an even greater processing load on the system). Thus, if speech is considered necessary then the best possible quality should be used. If speech is not considered to be vital in the particular circumstances then it may be best to simply present the message as text. If the context of the speech is to augment a written message then it should precisely duplicate the text. Given this situation, some compromise in quality may be acceptable as the information in the two messages will have increased redundancy and should be mutually supportive. However, it would still be necessary to test the particulars of any approach like this with an appropriately representative group of users. Finally, it is important to remember that the combined effects of noise and degradation on older people’s ability to hear and understand speech, tend to be multiplicative rather than additive100. Thus, if there is any doubt about the quality of speech when it reaches the user, the importance of suitable user testing cannot be emphasised enough.
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Chapter
6
dynamic elements
As mentioned at the beginning of the previous chapter (which addressed perceptual abilities), this chapter will cover issues of interface design more associated with older users’ cognitive abilities. That is, the discussion will focus more on the layout of interaction tasks which are beyond the bounds of a single screen presentation and require more of a sustained effort from the user. Also, as has been mentioned previously, very little research exists which has addressed issues of people and interactive systems which can be usefully generalised beyond the specific (and often work place oriented) task and system examined, and virtually none which has involved older people. Thus, the following discussions will be to some extent, necessarily speculative, although research that is relevant will be referred to as and when appropriate
Searching and navigation There is a large body of literature associated with performing searches, mainly with reference to particular software applications and other, more generalised situations in which the main aspect of the task is to identify, locate and/or retrieve specified information within a large database. Much of this work presents only a very loose analogy to the use of interactive television systems. That is to say, much of this work examines issues relating to specific forms of information search dialogue, rather than searching in general. However, some studies have been general enough in their design to offer potentially useful insights. For example, a comparison of the usefulness of an alphabetical subject index with a keyword search method on a variety of information retrieval tasks, found the latter to be both quicker and more accurate101. Similarly, it has been found, for novice users, that a keyword search was superior to using structured menus, especially if it incorporated an allied prompting system102. Findings such as these suggest that keyword searches may be a very useful approach for any interactive service involving a large catalogue of products or services. Anecdotal evidence from studies carried out by the present author add further support to this view (see Example M).
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However, the provision of any keyword search facility will require careful consideration to design efficient methods for users to input the search terms. That is to say, the studies mentioned above generally used a desktop PC with a full alphanumeric keyboard, an input device likely to be considered somewhat unwieldy in most television viewing environments. This and other issues related to input devices will be discussed further in the following chapter.
Example M: Searching a simulated interactive television service for Films and TV programmes.
A sample of 50 elderly volunteers took part in a ‘natural history’ study of a simulated interactive television service, with the aim of identifying the strengths and weaknesses of the interface with regard to elderly novice users. One element of this service was the provision of films and television programmes ‘on-demand’. Access to these was provided via a hierarchy of menu lists. In certain contexts this approach is appropriate on the basis that it requires recognition rather than recall (see Chapter 3). However, despite the fact that this simulation contained only about 12 films and 20 programmes, a sizeable number of volunteers expressed some irritation that the system’s allocation of items to categories did not necessarily match their own (ie one person’s action/adventure may be another’s comedy). It seems highly likely that such difficulty would become significant, given a larger size of catalogue. On the basis that a similar ‘real world’ service would be likely to offer a range in the order of hundreds (or even thousands) of items, it is likely that not only would this source of irritation be exacerbated but there also seems an increased likelihood that even a ‘perfect’ search would become overly time-consuming and cumbersome. A small number of the volunteers spontaneously suggested keyword searches, based on their experience of IT developments at their local libraries. Most of these also recommended the utility of different search ‘fields’. Given individual differences such as those indicated above103 and others, there does seem to be potentially great benefits in carefully considered ranges of search fields, but the ‘best’ approach will ultimately depend on the content of the catalogue and the needs, preferences and likely knowledge of the user. Using films ‘on-demand’ as an example it would be helpful to offer search fields which cater to people more interested in particular directors or actors or categories of films. Further, consideration of the user population as a whole may make it viable to offer fields such as, year of production, language.
Other work in this area has looked at differences in the structure and presentation of the database itself. For example, one study compared spatial and tabular presentations of two databases one involving airline routes, schedules and facilities, and the other, a thesaurus103. The volunteers in this study were given a variety of information retrieval tasks, the answers to which were designed to lend themselves more to one data presentation format than to the others (eg ‘How many flights depart at 10:45’ emphasises a tabular format and ‘which cities do you pass through between X and Y’ emphasises a spatial format). The general finding was (perhaps not surprisingly) that ‘spatial’ questions were answered better with the spatial format than with the others and vice versa. However, it is worth noting that in this context, it was also found that there were marked individual differences across these presentation formats,
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with different volunteers showing better performance for one particular format that was stable across all question types (ie there appear to be ‘spatial’ people and ‘tabular’ people). Other studies have produced analogous findings which support this idea104. These findings may be relevant to various aspects of interactive services. As a simple example, it may be appropriate to present bus timetables in a tabular format (the potential benefits of a more interactive approach notwithstanding) but it may be useful to also present the bus routes in a spatial format. In more general terms it raises the importance of giving careful consideration to the structure and presentation of any large corpus of ‘data’ (be it a library of films, an on-line shop’s product range or other information), and the ways in which users (with their own preferences, priorities and idiosyncrasies) can ‘see’ and access it. Other studies in this area may offer useful insights for those developing services which involve large databases. However, because of fundamental differences in content, the tasks and users involved, a comprehensive coverage of the findings is beyond the scope of this report. Thus, only a very brief overview and a few potentially useful source references are given here for those involved in such an endeavour. For example, studies have examined whether people’s search strategies in large databases are generally random or systematic105 and others have examined and described the preferred search patterns (and their efficacy) of people in databases with differing content, structure and interfaces106, 107. Various other studies have examined similar issues but in relation to different types of menu use, which may offer findings relevant to those involved in these aspects of interface design108, 109, 110, 111. Some work of this type however, has produced findings which can be generalised so as to offer some potentially useful suggestions. For example, various studies using a variety of materials, have indicated the general usefulness of ‘look ahead’ help fields112, 113, 114. That is, the availability of (usually fairly brief) additional information which expands upon the meaning of a menu item (or similar), with particular reference to the implications or outcome of selecting it. Thus, such ‘look ahead’ information helps users to understand where they are going with regard to their progression toward their goal. It seems likely that this kind of assistance will be of particular help to older users. In a similar vein, older users may also benefit (in some types of ‘search’) from ‘look behind’ information which may support their relatively poorer memory, with regard to previous aspects of their progress. Depending on the nature of the particular search task both of these types of information could be very useful. Similar research has been carried out in the area of Hypertext (also referred to as Hypercard) which has some useful analogies to the structural and functional ‘layout’ of many interactive television services. One example of this used a simulated tele-shopping system with tasks involving comparisons of prices and the availability of products across a variety of ‘virtual shops’. The findings of this study further supported the idea of the importance of relieving memory
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load in tasks such as these, with regard to both speed and accuracy of task completion115. In this experimental study the memory load was reduced by the provision of an integrated ‘notebook’ for recording information for later use and similarly a ‘planner’ for initially recording information about ‘what needs to be done’. However, these memory aids proved helpful in the context of a carefully structured simulation which ensured that all the necessary information could be entered by mouse clicks on a desk top computer. Thus, applying similar facilities to other ‘real world’ interactive services may require careful consideration of how their utility for the user may be maximised in a similar way. A similar but more general principle (based on findings from a variety of more theoretically oriented research) is the idea that whenever possible the screen should be used as an adjunct to working memory116. This includes elements such as the overt types of memory aid indicated above and also less apparent (to the user) techniques. Examples of this include, constraining progress through a task to minimise the amount of irrelevant information encountered by the user, presenting appropriate prompts and reminders, and basing as many as possible of the user selectable operations of the system on recognition, ensuring that any particular array of options used, are as distinct from each other as possible as this reduces the chance of false recognition (most of these issues have been mentioned in slightly different contexts in the previous chapter). Along similar lines to the work recommending ‘look ahead’ help fields (above), in the context of Hypercard applications, research findings have indicated that it is important, in this form of interface, that at any given point the screen display should clearly indicate the possible responses available in terms of both, where it will take you and what the consequences of that will be117. Other studies have described the utility of a ‘browser’ as a navigation aid within Hypercard type environments. In this context ‘browser’ refers to a variety of methods whereby users can access some form of overview of the network (complete or partial as appropriate) and their present location in it. This recommendation is qualified by the point that there will often be a need for a compromise between the amount of detailed information presented in the overview and the proportion of the network presented by it, due to limitations such as screen size. For example, one study examined four ‘browser’ formats (schematic and spatial, in two and three dimensions) in the context of an ‘academic department information system’ and the general conclusions reflect the findings mentioned above103, such that the degree of aid the different ‘browsers’ offered differed depending upon the type of task and the particular user involved118. Further, the findings suggested that in relatively small and simply structured networks a two-dimensional overview is appropriate while a three-dimensional one seemed to be more of a hindrance. Conversely, for relatively large networks with more complex structures a two-dimensional overview may have been
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inadequate to suitably represent the network’s structure. In general, the factors indicated above for aiding navigation through electronic networks are further supported by another study which developed a taxonomy of the types of problems faced by novice users, based on observations of their performance with an interactive database information retrieval task119. Thus, it is difficult to be prescriptive in this regard other than to reiterate the importance of giving careful consideration to the nature of network available to users, the ‘tasks’ which people are likely to carry out during their navigation and the particular abilities or expertise (or lack thereof) which users are likely to have. Differences of ‘network’ connection structure
Beyond the issues mentioned above, it is likely that the ability of users to navigate through an electronic network will be generally enhanced if the design of the interface is informed by knowledge of the structure of ‘network’ involved. That is, Example N shows some schematic illustrations of differing network structures, each contains a shaded ‘node’ which represents the default ‘start point’ or ‘home page’.
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Example N: Simplified illustrations of different types of ‘network’.
(1)
(2)
(3)
(4)
Illustration (1) shows a ‘simple hierarchy’, navigating through this sort of structure will be relatively straightforward to the user, however, it is also apparent that if a ‘wrong turn’ is made, retracing one’s steps and ‘returning’ to the correct place can easily become a time consuming process. Another limitation of this structure is that ‘expert’ users may find it excessively time consuming to progress in single steps and may prefer to go ‘straight there’. The extra connections in illustration (2) allows greater flexibility in the ‘routes’ that can be travelled (limiting the problems identified with the previous structure), but this is at the cost of an increased likelihood that users will need some assistance in order to avoid ‘getting lost’. However, this structure retains some of the elements of a hierarchy which makes it relatively straightforward to ‘retreat’ back to the ‘start point’. This becomes much less straightforward in the case of illustration (3) which represents a ‘fully connected network’. This is analogous to the ‘world wide web’ and it is worth noting that the applications giving access to this network all have a (constantly available) ‘home’ button which at least allows users to retreat to the ‘start point’ should they ‘get lost’. If however, the
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interface for this kind of network is more like a Hypercard environment (ie page based) rather than the ‘navigation toolbar’ environment common with the world wide web, then users will more likely need additional assistance to keep track of ‘where they are’. Illustration (4) shows the kind of structure that is most likely to be found with interactive television services. That is to say, it is a combination of the other types of structure. Such that some connections are for navigating between different services, while others are for navigating within services (eg carrying out an interactive task). Further, some sets of connections may represent ‘services’ connected to other parts of the network (eg a television programme listing service with connections to a separate ‘celebrity magazine’ service), while other services are totally self-contained. Taken together this indicates the importance of considering both ‘global’ and ‘local’ aspects of the network being provided in order to decide how best to offer ‘guidance’ to users.
Transactions Very little research seems to have been carried out in the area of electronic transactions (outside of specialised work based systems). Some work has, however, been reported on the effects of different types of response frame associated with electronic home shopping. Many of these are based on a study which indicated and described the three most common types of response frame in use in ‘real world’ applications at the time. These are labelled as ‘tailored’, ‘menu’ and ‘generalised’120. Briefly, tailored response frames relate to a single type of product, menu response frames relate to a limited number of similar products and generalised response frames relate to relatively large ‘catalogues’ of a wide range of products (the latter also tends to require specific knowledge on the part of the user, such as item reference numbers, etc). These types of response frame have been experimentally compared in terms of their usability for novices121. Perhaps not surprisingly, it was found that in a ‘single item purchase’ condition, performance was faster and more accurate with the tailored frame than with the others. The ‘multiple item purchase’ condition produced rather ambiguous results. However, it is apparent that these different frame types (like other aspects of layout, above) are suitable for different types of product purchase in different contexts. That is to say, a tailored frame is most suitable for a ‘one off’ purchase of a product that requires a relatively large number of attributes to uniquely specify it (eg a washing machine). A menu style of frame is more suitable for more generic items that tend to be purchased in groups from a limited set of categories (eg ‘staple’ groceries with options such as, milk [skimmed, semi-skimmed, full cream], butter [salted, unsalted], etc). A generalised style of frame could be suitable for either of these but in the context of a larger selection of items, however, as indicated above, this would require an additional body of information to help the user make their selections (eg indices, reference numbers, etc).
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Another form of transaction that has been studied is flight reservation and ticket booking122. However, the emphasis of the study was not the transaction per se, rather the method of information entry. In a sense this study examines another type of response frame. In this case the product is a ticket for a particular air flight, which will generally have to be selected from a very large database. This study indicated that the problem of various item selection methods for this kind of application was the very wide range of options in any particular field. Such that however the presentation was organised, it was always a somewhat time consuming operation. For text entry methods, the quickest and most preferred involved ‘autocompletion’ which offered an option as soon as it had been specified by the letters entered so far. The two other text entry methods took significantly longer than ‘autocompletion’ (and also slightly longer than the selection methods, although this simulation used a database smaller than would generally be used in a genuine application). However these other methods were clearly distinguished on grounds of preference. That is to say, one (‘immediate’ entry) received a preference rating intermediate between ‘autocompletion’ and the selection methods and significantly better than the other (‘delayed’ entry). The difference between these was that the ‘immediate’ method informed the user of ‘no match’ (due to incorrect spelling or the correct specification of an item not in the database) on completion of that field. Whereas, the ‘delayed’ method did not inform them of this until they had completed all fields. This strongly suggests that the lower levels of preference for this ‘delayed’ method are due to frustration. This also supports the points made in the previous chapter regarding suitable feedback about ‘errors’ (and easy methods of making corrections and alterations thereof) and other aspects regarding ‘progress’ through an interactive task. Another relevant study used a simulated car purchase task with volunteers basing their selection on a computerised database containing information about 10 different attributes of six different cars (eg fuel economy, purchase price, etc)123. Again the emphasis of the study was not on the transaction per se, rather on the use made of the information provided (it is explained that the information presented was designed so that there was no ‘best buy’). However, the main relevance of the study here is that it involved comparisons of old and young volunteers. The main findings were that there was no difference between old (mean age 65.7 years) and young (mean age 18.7 years) in the overall time taken to reach a decision. However, the older volunteers examined less information than the young (24% of all available compared to 33%, although it is worth noting that the data from around 20% of the older group was excluded from these figures as they only examined one item of information before making their decision). However, the older group spent more time viewing such information as they did examine (15 seconds per item compared to 7 seconds). Also, they re-examined less information than the young (two items compared to seven). Although it is unlikely that these findings would generalise to real purchases (particularly of something as expensive as a car), it
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does indicate that elderly people may benefit from being explicitly prompted to check and compare all the salient aspects of an electronic transaction before they commit themselves in any significant way. This general point is supported by further general recommendations from a review article which indicates the importance of presenting (non-expert) users with explicit information about the important aspects of a transaction (or other sequence of operations) before they commence116. Another recommendation is for the presentation of a summary of what has been done (and where appropriate, how) after completion of a ‘fatal’ operation (ie any operation that is effectively irredeemable and thus means the user is ‘committed’). These recommendations are given in the context of the work environment but it seems reasonable to accept the general similarity between an office transaction and a consumer one. This again, suggests the importance of giving useful ‘feedback’ which helps to ensure that the user (regardless of their level of expertise) knows what they are doing. Studies have also been carried out employing another form of interactive service which offer findings that seem relevant here, that is automatic teller machines (ATMs). Regarding ATMs it seems well substantiated that the elderly population tend not to like using them124. However, this is mainly due to fear of crime and feelings of vulnerability at the locations of many ATMs (hence the relatively recent move by many banks to offer ATM services in a secure lobby area). A task oriented study of ATM use has been carried out and the main emphasis was on comparing different methods of training older people to use them, some of the findings from this study are relevant here125. The first finding bears on the fact that the elderly sample were selected on the basis of having never used an ATM before. When asked why this was the case, the most popular answer (fear of robbery came second) was that they did not need them and were organised enough not to need banking services out of hours. It is however, likely that attitudes towards home banking are likely to be very different to those of ATMs (particularly for the less mobile) as it involves the added ‘convenience’ of not having to leave the house. However, it should be borne in mind that another popular reason for having not used an ATM was a preference for personal contact with the teller. At present it cannot be said whether this preference for personal contact or that for the ‘convenience’ of not travelling to the bank is the more powerful. Thus, it would be important for anyone planning such a service to examine such issues carefully. Another main finding was that those volunteers whose performance benefited the most from training showed a marked improvement in their attitude toward ATMs in general and in their intention to use them in the future. This is another illustration of the importance of a positive initial experience with novel technology (mentioned in Chapter 4). Further to this and regarding the training methods compared, it was found that ‘passive’ training was generally unsuccessful but that the ‘active’ methods both produced similar significant
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improvements. The ‘passive’ form of training in this case consisted of simply showing a demonstration of the system being used. The two ‘active’ forms of training involved the following. One was a ‘flash card’ training session using a progression of questions and (prompted) answers to guide the volunteer through the meaning and the steps of the various transactions. The other ‘active’ method used a ‘hands on’ interactive task involving an interface physically laid out in a very similar way to the actual ATM and with equally similar procedures, but with a content that was related to ordering a specified meal. These findings seem to offer a useful insight into the possibilities for helping older people overcome the initial ‘fear of the unknown’ regarding an interactive system so that they are more willing to experience and subsequently appreciate such benefits as it can afford them. Another informative study has been carried out involving younger and older users of an ATM126. The main emphasis of this study was the view that ATMs should be ‘walk up and use’ and the findings generally support some of the points made above (and in the previous chapter). Briefly summarised, the main findings were as follows. They found that the elderly users made disproportionately more mistakes following screen presentations containing more than one instruction, leading to the recommendation ‘One screen frame, one instruction (one sentence, one meaning).’ In a similar vein (and emphasised by the latter part of the preceding quote), was the finding that the instructions which caused the elderly (and some younger) users the most difficulty were those containing any ambiguity, both of these issues have been addressed in the previous chapter. Of somewhat more relevance here is the finding that many of the mistakes made by all users (but particularly the elderly ones) were due to the system imposing an order of operations which did not match that which made sense to the user. This suggests that the designers of the system did not address the expectations and ‘mental models’ of prospective users and instead seemed to have been guided by what was ‘efficient’ for the system itself. Related to this, was the finding that some of the imposed ordering was not made apparent to the user with ‘highlighting’. This problem was most apparent in the task involving transferring funds from one account to another. That is to say, confusion began because the system imposed an order of events where details of the account the funds were going to were input first, followed by details of the account the funds were coming from. Perhaps not surprisingly, the volunteers in this study expected this order to be the other way around and entered the details accordingly, even though information was available on the screen to indicate that this approach was wrong. Despite the mismatch with the users’ expectations it seems likely that the number of ‘errors’ made in this task would have been reduced had the on-screen instructions been appropriately highlighted (eg ‘details of the account funds being transferred to.’ and ‘…transferred from’). Finally, they found that many of the errors made, particularly by the older users, stemmed from varying degrees of disorientation
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when a new screen was encountered. Although such errors occurred in differing contexts, the impact of new screens per se, was indicated by tracking the on-screen locations viewed by the volunteers. On the bases of these types of difficulty the experimenters indicate the importance of guiding the users’ gaze (and thus attention) to the relevant ‘start point’ of any new screen. This and related issues will be addressed in the following section.
Screen transitions As indicated above, and elsewhere in this Style Guide, it is apparent that older people can be relatively much more disoriented by screen transitions than younger people (who also tend to be more familiar with the general ‘computer’ environment). In general, it would only be cases of extremely bad design which could make the screen transition itself disorienting enough to cause an older user to terminate the interaction and ‘give up’. However, bearing in mind that during an interaction, the user will need to hold a variety of different information in memory, even a slight degree of confusion or disorientation when a new screen is initially encountered can be enough to disrupt their memory and it is this ‘knock-on’ effect which is most likely to interfere with completion of the interaction. Much of the discussion in the following sections of this chapter covers issues which have been addressed in differing contexts previously in this Style Guide, but the aim here will be to describe useful approaches in more general terms. Prompts and reminders
The first general approach involves explicit forms of guidance, such as giving particular prompts and reminders. As indicated previously, the particular way in which these are most suitably presented will depend entirely on the amount and type of the cognitive demands being placed on the user at the point in the interaction when the new screen is encountered. In simple terms, at the early stages of an interaction the emphasis will be on prompting the user with the aim of matching their expectations (and intentions) about what they will have to do and in what order, with the relevant requirements and constraints of the system. Toward the latter stages of an interaction the emphasis moves more onto reminding the user about what has (and has not) been done so far (particularly if previous operations can place constraints on subsequently available operations), and the presentation of any other information that would otherwise have to be ‘recalled’ or ‘calculated’ by the user (with these terms defined in their broadest senses). In order to decide the best way of presenting explicit information of this kind it is first necessary to have a clear understanding of the ‘abilities’ of the interactive service. That is, the actual ‘service’ being provided and the particular way(s) in which the system has been designed to allow users to access it. If this design has been usefully informed by prior knowledge of the ‘abilities’ of potential users, then it is likely that the overall necessity for prompts and reminders will be reduced, it is very unlikely however, to have been eliminated. If, on the other hand, the design of the service has
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not been so well informed about the ‘abilities’ of the users, then it is vital that the design of the prompts and reminders employed are. Thus, it seems to be basically inevitable that all interactive services require prompts and reminders to some extent. In other words, no interactive service is immediately transparent to a user. Therefore, it seems reasonable to assume that the most relevant aspect of the ‘abilities’ of potential users is a lack of specific knowledge about the functioning of the particular system in question. Thus, those with sufficient knowledge or ‘mental adaptability’ to successfully complete the interaction unaided (ie ‘expert’ users), can simply overlook such ‘irrelevant’ information without any inconvenience. Which means that this kind of information can best be presented by considering the needs of those users with the most limited ‘abilities’ in this regard. With regard to knowledge of the particular system, those most limited in this include the following. There are ‘novice’ users who have no previous experience with this particular system and may or may not have had experience with other similar systems, or even other similar ‘services’ (ie in the ‘real world’). Similarly there are ‘occasional’ users, who may have used this particular system before, but may be equally (if not more) familiar with other similar systems (or equivalent ‘real world’ services) and thus may confuse similar but distinct procedures, and will be more likely to do so the longer it is since this particular system was last used. Regardless of the other limited abilities of older people described in earlier chapters, and in relation to electronic interactive systems, they are more likely to fall into the latter two categories, and thus are the best group of potential users to consider for the specific design of prompts and reminders. Also, the tendency for limitations in longer term aspects of memory in older people increases the likelihood that although they may use a particular service often enough to be described as a ‘frequent’ user (which may often imply an ‘expert’ user), they may actually continue to behave more like an ‘occasional’ user (or even a ‘novice’ user). Guiding attention
The previous section related to presenting (mainly) written information to explicitly inform and guide users through an interaction. Another explicit approach to this is the use of highlighting, some aspects of which were outlined in the previous chapter. This approach is related less to the overall interaction and more to the actual transition from one screen to the next. That is to say, highlighting is most useful for drawing users’ attention to the most salient (informative, introductory, etc) element of a new screen. In other words, each new screen indicates its own ‘start point’. The amount of highlighting needed may often be limited by consideration of certain characteristics of the new screen and the one(s) immediately preceding it. For example, if prior screens have generally been of textual layout then the user will most likely attend to the top-left portion of a new screen. If this ‘expectation’ is realised (either with another instance of textual layout, or with the placement of some other form of ‘start point’), then the need for specific highlighting is meaningfully reduced. In this sort of situation such highlighting may ‘bow out’ if in competition with another highlighting scheme related to the content of the surrounding screens.
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It will most often be the case however, that the designer does not have such a basis for assuming which particular screen location will be attended to in this way. In these situations many of the uses of highlighting described in the previous chapter are relevant. However, because of the almost unlimited range of possible pairings of screens on either side of a transition, it is worth describing some of the main aspects of highlighting needing consideration, in more general terms. For example, it is useful to consider the ‘scale’ of a highlight in relation to the relative ‘precision’ required to unambiguously indicate the position of the target location. That is to say, bearing in mind the content of the current interaction, and given the layout of the new screen, it is important to decide whether it will be most beneficial to draw the users’ attention to a very specific screen location (eg a small and otherwise unobtrusive ‘instructions’ button) or to a more general area (eg a panel of introductory text or an array of ‘headings’ or similar). In a similar way it is useful to consider the relative ‘importance’ of a particular ‘start point’ in relation to the general ‘impact’ the highlight is designed to have. For example, it might be considered important in some circumstances to ensure that one particular screen location is attended before any others, in which case it would be most suitable to design the highlight with a relatively high level of impact. In other circumstances it might be that it is important that a screen location is attended to at some point but that it is inconsequential if other locations happen to be attended to first, in which case, somewhat less impact is necessary. In other circumstances still, a certain location may be considered interesting (rather than important, per se) to the user and so would be best indicated by a highlight with relatively low impact. Another potentially useful approach to guiding users across screen transitions is ‘pre-highlighting’. That is, there may be situations where the user is best served by having their attention drawn to a particular location on the screen immediately before the new screen appears. For example, an area could be briefly highlighted by a localised ‘flash’ of colour during the transition, such that by the time the user is looking there the highlight is gone and the relevant ‘highlighted’ area appears at the fixation point. Another possibility would be to use some kind of animation as the transition, which has the added benefit of making the change between two screens less abrupt. For example, the ‘old’ screen could ‘shrink’ (revealing the new screen from the edges in) and finally disappear at the required position. Alternatively (and possibly most useful for textual layouts), the ‘old’ screen could be scrolled away like a page, with the bottom right-hand corner being ‘pulled’ to the top left, to draw the users’ attention there for the next page. These explicit approaches to orienting users during interactions are important and will often be necessary. However, the need for these can be limited if the
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user has accurate expectations about what is coming up. As mentioned above, an example of this is that while reading text a user will expect the text on the next screen to start in the ‘usual’ place. It is apparent that this expectation is based on familiarity with the general conventions of text layout. It is also apparent that such conventions develop because they are consistent examples of how something is done. Thus, ensuring consistency in an interactive system will likely benefit all users but particularly older ones. Some of the relevant aspects of consistency will be discussed in the following section.
Consistency Certain aspects of consistency have been addressed previously in this Style Guide. However, it is worthwhile describing some of the main considerations in more general terms. In a sense the key point here is that consistency breeds predictability. As indicated above, if older users of interactive systems can predict what is likely to happen next, then many of the difficulties they may otherwise experience can be overcome. Consistency (and thus, predictability) plays a role at all levels of a user’s interaction with a system. To give an idea of some of these levels, some very general examples will now be outlined. An example of a ‘local’ consistency issue can be related to the cinema booking service indicated in Chapter 5. As described, the user selected from a sequence of criteria but this relatively straightforward task was made difficult by the inconsistency that some criteria were selected from lists with one button press and some by two (ie ‘select’ then ‘activate’), additionally, one of the criteria (ie number of seats required), rather than being selected from a list, was directly entered as a numerical value. It is likely that less confusion would have been caused if each set of criteria used the same selection method. Such that each set of criteria could be laid out in similar ways so that the desired choice could be ‘highlighted’ and then ‘entered’. Similarly, beyond a single ‘interaction task’ consistency may be helpful at a slightly broader level. For example, if a significant part of an interactive system is an ‘infrastructure’ which allows users to navigate to a variety of different services, it would be helpful to older users if the selection methods of the different ‘routes’ were similarly consistent. That is to say, depending on the context it may be considered more suitable to use numbered lists with numerical selection (preferably two-step) or just headed lists with arrow key selection (again, two-step). Each of these approaches will have different strengths and weaknesses depending on the situation (ie the relatedness or diversity of the services offered, the number of options available on each screen, and so on), however, it should always be possible to organise the presentation of options so that one consistent method of selection can be used throughout.
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At a broader level still, there may be situations where an interactive system includes differing services, which (despite their apparent differences) involve similar interactive operations. An example of this could be a ‘films on demand’ service and some form of ‘home shopping’ service. The main similarity between these services is that the user will need to search through a relatively large catalogue for a particular item. Thus, it would likely be beneficial for users if these ‘search interactions’ were presented and operated in generally similar ways. It is apparent that this latter example may be more difficult to implement than the others as the differing services involved may be provided by entirely separate organisations, each of which may feel that their approach is ‘best’. Although by no means a simple solution, the decision as to which approach should form the basis for a consistent ‘model’ ought to be based on suitable user testing. Depending on the situation, this could indicate that one or other (or some alternative) approach is ‘best’ or it may be possible to weigh up the benefits of two ‘good’ approaches against the extent of any negative impact caused by the inconsistency between them. Further to this, the ability to harmonise services in this way may be even more problematic in the case of separate organisations which provide essentially the same service. Because of the inherent competition that is likely to exist between such services, it is even more likely that the organisations involved will be resistant to such suggestions. However, in such situations it is important to point out that consistency in this sense does not have to equate to ‘sameness’, and it should always be possible to present the user with the benefits of predictable operation sequences, while at the same time giving a particular service a distinct ‘lookand-feel’ based on the preferences of its provider.
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Chapter
7
input elements
Previous chapters have mentioned that, for many interactive tasks the most suitable on-screen layout is, to a greater or lesser extent, determined by the input method available to the user. This chapter will discuss issues related to the use of various input devices by older people. First, standard or ‘traditional’ devices will be addressed, followed by some of the possibilities offered by more novel approaches. The chapter will conclude with a discussion of some of the general issues surrounding the provision of suitable devices for differing ranges of interactive service.
‘Traditional’ remote control devices It would appear that currently the most common approach to user input for interactive services is based on the ‘traditional’ type of TV/VCR remote control. In some cases the unit will have additional keys for use in interactive services, while in other cases, the remote control will have a ‘standard’ layout of keys, some of which are assigned additional functions for interaction purposes (ie numeric keys, see Example G). The following discussion will cover some of the main issues involved in using these types of devices for user input by elderly people. Subsequent sections will then discuss some of the general issues involved in using other, rather more novel methods and devices for user input. Several of the system evaluation studies carried out by the present author have indicated some general difficulties older users tend to have with these kinds of ‘traditional’ devices. Some of these difficulties were most directly related to uncertainties about the mapping between available and desired functions and the particular key presses required (see Chapter 5). There are also a variety of difficulties related to using the handset per se. These included problems for some older users of the buttons being somewhat too small, too close together, with unclear labels and lacking in sufficient tactile feedback to indicate that the button had been pressed ‘properly’. Unfortunately, little specific guidance can 81
be offered on these issues as there appears to be virtually no anthropometric or other human factor data related to older users of such devices. One report of an observational study was found in the literature, which indicates similar difficulties to those mentioned above and also decries the paucity of relevant ‘background’ measures127. In a similar vein, an article has been published which specifically (and in great detail) argues for the need for such data44. In general, the conclusions from this article are that what little data exists regarding elderly people are generally based on older (working) males. This is poorly representative of the older population because of sex differences in mortality rates, such that for those aged around fifty, for every 10 women there are only nine men, for those in their 60s this drops to about seven and in their 70s and 80s there are only about half as many men as women. This is compounded by the tendency for elderly people to be grouped into a ‘catch-all’ category usually labelled ‘65+’ or similar. This is particularly unhelpful as it is generally accepted that there are many meaningful differences in ability throughout this older age range (some of these are described in Section 1 of this Style Guide). Related to this is the fact that any particular age group of older people (compared to similar age range of younger people) will tend to show broader variation along many dimensions, which blurs the boundary between what is normally considered anthropometrically ‘normal’ and ‘extreme’. The issue is also raised, that the type of measures employed in standard anthropometric studies does not include ones relevant to many aspects of modern technology. For example, data will exist about measures such as ‘arm reach’ and ‘arm strength’ but not about more ‘dynamic’ aspects such as manual dexterity or sensitivity to the ‘resistance’, ‘give’ and/or ‘click’ of a button. It is hoped that such gaps and weaknesses in these areas of research will soon be improved. Subsequent editions of this Style Guide will include any such updates as they emerge. During the interim however, this situation further emphasises the need for suitable user testing. Beyond the difficulties older people have with the physical handling of ‘traditional’ remote control units, the relatively large number of buttons involved presents a further barrier to ‘effortless’ interaction. That is, several problems have emerged in our system evaluations because the number of buttons on the handset (in this instance, 36) effectively prohibited the possibility of memorising the location of each. The consequence of this being that, regardless of the user’s knowledge (or not) of which particular key to press at a particular time, the user must switch (both visually and attentionally) from the screen to the handset in order to locate and press the required button. In other words, users of this system are in effect dealing with two separate interfaces, both of which are involved in the performance of the same task. In terms of cognitive ability it has been established that this kind of situation is detrimental to levels of task performance of many elderly people128, 52. This ‘two interface’ situation also causes various pragmatic difficulties. For example, many older people require different corrective lenses in order to focus
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on things within arm’s reach (ie the handset) and at significantly further distances (ie the television screen). Our system evaluation studies have produced a variety of different difficulties for some of the elderly volunteers. For example, there was the difficulty of putting on and taking off up to two pairs of spectacles and, particularly in the case of two pairs, ensuring that the pair currently not in use were placed somewhere safe yet easily accessible for when next required. It must also be remembered that the handset itself is also part of this juggling act. In a similar vein, some volunteers (regardless of corrective lenses) would raise the handset up towards their face in order to read the button labels, locate the appropriate button and press it. This often meant that the handset was pointing up at the ceiling rather than at the set-top-box, so that the keyed command was often not received by the system. Thus, the volunteer, believing they had input a command, would return their attention to the screen only to find that they had to go through the whole process again. These issues argue for the general benefits (particularly for older people) of simplifying the handset, preferably to an extent where after only brief familiarisation a user’s attention need not be drawn away from the main, onscreen interface. One approach to simplifying a handset may be to reduce the number of buttons, but assign relatively more functions to each. In some circumstances this approach may be suitable although it should only be pursued with great caution. That is to say, although this approach may reduce the memory load regarding where each function/button is on the handset, it will likely increase the load regarding which function relates to which button and when. If an interactive environment can be designed where this trade off works in favour of the (older, novice and/or occasional) user then such an approach may be suitable. However, it should be remembered that (other difficulties notwithstanding) if the location of a button is forgotten it can relatively easily be found by looking at the handset, on the other hand, it is likely to be somewhat more problematic to find a suitable memory cue if what has been forgotten is a ‘rule’ about which button will produce a required function at a certain time. Another possible limiting factor in how far a control device for this kind of system can be simplified would be if substantial alphanumeric input were required. The systems evaluated by the present author have indicated only a very limited need for this, with the vast majority of input being the selection of one from a set of options. The only alphanumeric input required in these systems was occasions of entering a four digit PIN (personal identification number) required to ‘log-on’ and for certain on-line purchases. However, as noted above, it is likely that future developments may require more alphanumeric input, for example as archives of films and programmes available to ‘view on demand’ grow in size, finding the desired item via option selection will become increasingly cumbersome and problematic. It is, therefore, likely that some form of ‘key-word’ search facility would be more suitable, but this
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would require alphanumeric input. However, as the amount of such input would still be relatively limited it could well be suitably achieved by locating and selecting items from an on-screen (or ‘virtual’) keyboard. This kind of input is commonly used for entering the highest scoring names in video arcade games. Thus, assuming the feasibility of using on-screen keypads, the main requirements of a simple control device for a system like this, is that it can indicate any on-screen location and indicate when that particular location has been ‘selected’ (see Chapter 5). In the context of desktop personal computing there are a wide variety of such devices currently available with many variations on existing themes emerging on a regular basis. It is also extremely likely that future innovations will further add to this diversity. As new and relatively distinct control devices have emerged there has been a tendency for ‘usability’ type studies to compare several such devices with the apparent aim of indicating which is ‘best’129, 130. More recently, however, there has been greater acceptance of the view that it is somewhat inappropriate to describe control devices along a generalised, single dimension of ‘good’ and ‘bad’. This view stems mainly from the emergence of various conflicting findings from such studies. One review of this research area succinctly summarises this finding by stating that: ‘The simple reason for the conflicting conclusions is because no single device is better than any of the others. Differences in the experimental task, the environment and the particular design of the input devices used have a large effect on the findings’131. In other words, it is currently more accepted that whether a device can be considered ‘good’ or ‘bad’ ultimately depends upon what it is being used for132, 133, 134 and who is using it94, 127. There is a further aspect regarding what the control device is to be used for, which deserves explicit mention. That is, much of the research that has examined control devices, has done so in the context of ‘the work place’, which generally assumes a desk-top PC, with the screen in close proximity to the users’ face and some amount of free desk space for the control device(s) to be placed and/or used on. It is apparent that this represents a somewhat different ‘environment’ to that of a television viewer sitting in a comfortable seat in their living room. This ‘work place’ perspective also carries with it an implicit acceptance for some degree of training leading to proficiency. Whereas, in a ‘home entertainment’ context it is much less likely for there to be such acceptance, to the extent that the most likely expectation will be for a system that is ‘walk-up-and-use’. Input devices which can specify an on-screen location and select it fall into two basic categories on the basis of whether they allow direct or indirect control. Direct control indicates that specifying an on-screen location is achieved by
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indicating the position on the screen itself with some form of stylus (eg light pen) or with the finger (eg ‘touch screen’). In one sense this method of control is ideal for elderly, novice users as it eliminates the difficulties of attending to a secondary interface. It is probably for this reason that touch screens are so popular with designers of public access systems83. However, the necessity for the screen to be comfortably within arm’s reach means that this form of control would generally not be particularly suitable for a home television viewing situation. Indirect control, on the other hand, allows specification of an on-screen position from a location (and often in a plane) physically separated from the screen. A common example of this is the ‘mouse’ which can be moved around in a horizontal plane on the desk while the co-ordinates of such movement are translated into the vertical plane of the computer screen and the position indicated by a graphic ‘pointer’ or ‘cursor’. A variation on the theme of the mouse is the ‘track-ball’ which in a simple sense is a mouse turned upsidedown. Thus, instead of the whole unit being moved around on a surface, the track-ball housing remains stationary and the ball rotated in the required direction(s) by the users’ hand or fingers. Joysticks also fall into this category and there is also a wide range of variations on this theme. For example, there are ‘absolute’ and ‘isometric’ versions. With absolute joysticks, control is similar to the mouse and track-ball inasmuch that movement of the joystick’s arm (relative to its central location) is mapped directly onto movement around (the centre of) the screen. Isometric joysticks, on the other hand, translate force into motion, such that the unit’s arm does not move but the pressure against it is measured and translated into on-screen motion. This translation can be either; ‘rate (or velocity) controlled’, wherein the direction of pressure on the arm only is detected and on-screen movement occurs at a fixed rate in the appropriate direction; or the direction and the degree of force are measured with the latter being translated into relative speed. Control similar to a rate controlled joystick can be achieved with a set of directional arrow (or cursor) keys, although this method often has fewer degrees of freedom and will tend to require some period where the keys need to be attended to until their locations can be memorised and located with no need to switch attention away from the screen. Many home video games consoles now use a controller that is midway between a joystick and cursor keys. That is to say, instead of (four or eight) separate keys there is one ‘rocker’ switch, the user places their thumb centrally on this switch and ‘rolls’ it in the required direction. Other key-press methods of control are also available but generally relate to screens on which movement is constrained in some way. For example, many of the studies comparing control devices (mentioned above) did so before high resolution graphic monitors were as widely available as they are today and thus, used screens constrained to the presentation of alpha-numerical displays only. Thus, the screen was effectively divided into a grid of cells each the size of one character. In this context cursor keys worked in discrete steps, with
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each key press moving the cursor from one cell to the next. Under these constraints (and with the accompanying emphasis on text presentation) keys could be assigned functions such as: (move to) top/bottom of screen, next/previous paragraph, next/previous word, etc. It can be seen that this form of control involves somewhat less spatial mapping and relies more on semantic mapping. Current software allows graphic screens to be constrained in analogous ways. Although this would likely limit the ease of spatial (and directional) control, it would allow any form of semantic control which was appropriate to the context. An example of this would be to assign on-screen locations different labels so that the user indicates the required one by pressing a key with the same label. A commonly used method of this type is to associate a number with the ‘label’ of on-screen locations (‘items’) and ‘move’ the cursor to that position by pressing the appropriately numbered key. Similarly, arrow keys could be used to ‘jump’ between constrained screen areas on the basis of being ‘close to’ the direction specified, rather than using the arrow directions in a precise way to ‘aim’ a pointer over the required item. Another general method of indirectly indicating an on-screen position is similar to the direct methods mentioned above except that the position is (directly) indicated on some form of panel (separate from, but generally the same shape as the screen) and the position indicated on the panel is translated to an analogous position on the screen. Comparisons have been carried out between on-screen and off-screen ‘pointing’ tasks and while each method has different (again, mainly context dependent) strengths and weaknesses129, both seem to allow equal speed, accuracy and general ease of use for simple spreadsheet editing tasks135. When separated, the relative sizes of panel and screen may vary widely depending on the context of their use. Graphics panels (‘tablets’) generally used with a stylus, are often a similar or larger size than the screen, whereas ‘touch pads’, usually operated with a fingertip, tend to be smaller than the screen. It is apparent that of the devices outlined above, some are more suitable for a home television viewing environment than others. Until recently most of them would be unsuitable due to the necessity for cables to connect the device with the computer/television. However, recent developments to a large extent have done away with this necessity, as many of the devices mentioned are now available in versions which transmit information via an infra-red (or other ‘wireless’) connection.
‘Novel’ approaches to user input Recent technical developments have opened the door to the possibility of new types of control device which effectively blur the distinction (made above) between direct and indirect control. That is, unlike the devices described so far
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which record movement (etc) themselves and transmit this to ‘the system’, these newer devices come in two parts one (the ‘sensor’) is placed near (or around) the screen and the other (the ‘device’) is held in (or attached to) the user’s hand. At present there are a variety of aspects of the device that can be measured by the sensor. That is, it may detect the position of the device in an invisible, delimited plane projected somewhere in front of the screen (ie as if this plane were a ‘virtual’ graphics panel). Alternatively, it may detect the relative motion of the device in a (non-delimited) plane; an example of this may be the identification of ‘directional gestures’. It is also possible for the sensor to detect the position of the device, its distance from the screen and its orientation, and thereby calculate the on-screen position being ‘pointed at’. Many devices of this kind are readily available at present, ranging from versions about the same size as a computer mouse which will sit comfortably in the hand to ones around the size of a (large) finger ring. ‘Data glove’ input
A development stemming from similar approaches has yet to become as widespread but undoubtedly will become so as the technology becomes more economically viable. Generally, this type of device is referred to as a ‘data glove’, and, in addition to information about position and orientation (as above), can input information about the ‘posture’ of the hand. It is apparent that in this context the relative complexity of the sensor system will determine the range and diversity of ‘gestures’ which can be distinguished. This form of input seems to have great potential for improving many of the difficulties inherent in the ‘two interface’ situation, mentioned above. That is, it allows the provision of ‘virtual’ (on-screen) ‘control devices’ and thus integrates the two (handset and screen) interfaces into one. The only significant drawback of this approach is that it raises the relative emphasis on careful use of screen space and design of the layout to take into account the virtual controls. Depending upon the nature of the overall interactive system involved and the services provided within it, two general approaches toward efficient use of screen suggest themselves. The first of these could be a ‘ubiquitous’ set of controls which could be either constantly present on the screen or ‘called up’ when necessary. An example of this approach could be something similar to the ‘toolbars’ presented in world wide web browser software. A major consideration for this approach is whether all the required functions could be adequately represented on the ‘toolbar’ whilst maintaining enough screen space for the ‘main’ presentation. Also, a particular strength of this approach (particularly for elderly, novice and/or occasional users) is that it has the general benefit of identifying buttons on the basis of recognition and that, given consistent placement, it should allow the possibility of implicitly learning the locations of them, meaning that more cognitive resources are freed for the interaction task itself.
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Another approach would be the presentation of a variety of ‘context specific’ sets of ‘virtual controls’. This approach would be most beneficial if different services within the same interactive system required very different (and nonoverlapping) functions, so that only buttons representing immediately relevant functions need be displayed at any one time. Again, depending on the circumstances it may be appropriate to present the controls for all of the time they are relevant or allow them to be ‘called up’ by the user as necessary. Because of the electronic nature of these controls they can be designed to be highly specific to their immediate context. An example of this could be that any time a user selects a sound recording, a set of suitable audio controls could be presented. Similarly, selection of a video, could be followed by presentation of suitable video controls and audio controls. The layout of each set of controls should remain as consistent as possible so that users can capitalise on their familiarity, whether they appear alone (ie audio controls) or as an element of a ‘compound’ set (ie audio/video controls). Also, the potential diversity of the sets of controls used means that it is extremely important that not only are they relevant to their context but also that the nature of their relevance is made clear to the user. The potential ‘richness’ of the information a ‘data glove’ can provide should allow the designer more scope for making the function of controls more apparent to the user. One example of this might be that ‘pointing’ at an item brings up a description of its function (or content) and that another ‘gesture’, such as ‘grabbing’ the item could ‘activate’ it. In addition, the control could suggest its function in a more ‘natural’ way, such that audio volume could be indicated by ‘twisting’ a ‘dial’, or the screen (page) could be changed (turned) by ‘picking up’ its ‘corner’. It would seem that only imagination (and the results of suitable user testing) would limit the range of possibilities in this regard. Although many older people will have the extent of their hand movement limited by factors such as arthritis and would be likely to tire relatively quickly, input approaches analogous to a ‘data glove’ could well prove very beneficial. One very important consideration in this regard would be how the ‘virtual hand’ and its diverse ‘gestures’ would be represented on the screen. In general, the principles described in Chapter 5, regarding aspects of on-screen pointers, would apply. Such that the pointer is clearly visible (without obscuring too much background), can be easily ‘aimed’ at targets and can clearly indicate to the user when they have achieved a particular ‘gesture’. Voice input
One of the studies comparing control devices cited above, concluded that none of the devices used seemed suitable for elderly people136. On the basis of this the researchers recommended voice input as suitable for older users. However, this cannot be considered as a simple solution to the problem of elderly users’
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input. In part, this is due to technical limitations. That is to say, despite undoubted progress in recent years, voice recognition software is still somewhat limited, mainly in regard to the size of vocabulary and/or the range of different speakers that can be effectively handled. Regarding elderly users, there is the additional difficulty (for the software) that they will tend to present relatively greater variability in a variety of their voice characteristics, mainly due to age-related changes to the vocal chords and other articulatory mechanisms22. This can include the voice ‘cracking’ which can make the fundamental and other harmonic frequencies change suddenly, similar but much more widespread is for the voice to ‘waver’ which involves less dramatic, but similarly unpredictable changes in frequency. These kinds of change are most apparent over short durations such as during a single utterance. However, it is also the case that analogous changes can occur over longer periods, for example, between similar utterances made on different days. This latter will probably prove particularly problematic in the context of systems which ‘learn’ voices on the basis of ‘training’ material spoken by a particular person. Other factors could also be important, such as the tendency for the older population to have relatively strong regional accents and/or dialects. It is likely that continuing technological development will overcome or at least limit the extent of these problems. However, there are other difficulties related to using voice input for interaction tasks. Some of these stem from age-related changes in memory. For example, voice input will generally offer little memory support as available commands will need to be recalled, although recognition could be used for simple selection of items from lists, wherein the item’s label (or associated number) could be seen on the screen and spoken. If voice input was to be used for item selection in this way it would be very important to make it a ‘two-step’ selection process (see Chapter 5), with appropriate highlighting, in order to avoid the frustrations attached to inadvertent errors. To achieve the variety of operations and functions available to the other types of input control outlined above, it seems likely that voice input would need a sizeable vocabulary of commands to be learned by the user, which may prove to be problematic in practice. Another aspect of this involves the problems related to the type of operations which require information based on a ‘sliding scale’. An example of this would be adjusting a volume setting, in other contexts this would be achieved by turning a dial or similar. For televisions a key can be pressed, either once and held with an on-screen indicator adding/subtracting increments on a scale, or each increment can require a separate key press. For voice input the only analogy to these would be the latter with a command per increment (eg ‘up, up, up,’) which may not be considered desirable by users. Another likely problem for voice input is that voice recognition systems (analogous to older people themselves) tend to have difficulty dealing with competing ‘noise’. Given that the context here is interactive television systems, it seems likely that there will often be situations where commands given to the system will have to compete with sounds being produced by the system. Even if a microphone is placed near to the user there is still a chance of interference. A rather extreme example of this would be that the user has selected a video to watch and has given the voice command to ‘play’, when the video runs it is immediately apparent that the volume is too loud, but because of this the system cannot ‘hear’ the command to turn the volume down. 89
There is also the possibility of similar difficulties due to other ‘noise’ sources not related to the system itself, for example it would be particularly frustrating for users who happen to live near busy roads or rail lines, to only be able to interact with their system when there are no cars or trains passing. Thus, while there are certain possibilities that voice input may realistically play a role in interactive television systems it is by no means a universal panacea for older users. Even if technological advances continue to improve regarding speech recognition to a point where systems can be claimed to deal with ‘natural language’, there will still be a host of difficulties regarding, information systems understanding ‘real’ natural language (including all the ‘errs’, ‘uhms’ and ‘you knows’) and users’ ability to understand precisely what they do (and do not) need to ‘tell’ the system. The above discussion indicates that although many of the input devices described have some potential to be beneficial to older users, most also tend to have significant limitations regarding the range of situations to which they can be usefully applied. This suggests the possibility of combining aspects of different input types into more suitable (for the whole system and the user) devices. Some of the main implications of this will be briefly discussed in the following section.
‘Specialist’ vs ‘Universal’ input devices It has been mentioned above and in earlier chapters and in a variety of contexts, the need to consider the ‘needs and requirements’ of the interactive system (that is, the whole set of services and their required operations) and to combine these with the ‘needs and requirements’ of all potential users, particularly older, novice and/or occasional users. It is only on the basis of this knowledge that a decision can be made about the most useful and ‘easy to use’ devices for that set of services and that set of users. Throughout most of this Style Guide the focus has been on the diversity of needs and requirements of older people regarding the most suitable screen presentation layouts, interactive task layouts and input devices. Regarding the latter, the extent of this diversity means it will most likely be best to offer a range of control devices, from which people can choose the one that capitalises on their capacities and avoids the limitations of their incapacities. To illustrate this, assume an interactive system which only requires ‘selection’ of an onscreen location and ‘activation’ of the indicated item. It is apparent from the above that there will be a range of potentially suitable control devices some of which will suit the abilities of some older people while some will suit the (different) abilities of others. Such as, a person with limited movement in their wrist may find it relatively easy to use a joystick that is large enough to be operated by arm movements (with an easy to press select button either on the hand grip or on the base). Another person may have trouble making such large arm movements and would perhaps prefer a small joystick (or rocker switch) which only requires finger movement. Yet another person may have difficulty
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with the kind of (relatively precise) mapping required (between hand movement and on-screen movement) with a joystick and may find it easier to use a keypad (using direction buttons or similar), while someone else with a similar mapping problem and arthritic fingers may prefer a device that allows them simply to point (or gesture) at the screen to select an item and to possibly (should a button press be difficult) give a spoken command to activate it. It is apparent that some interactive systems will involve services which require input which lends itself less readily to simple ‘point-and-click’ (the impact of ‘virtual’ control devices notwithstanding). This sort of situation may impose some lower limit on how simplified the required control device may be. Perhaps the most extreme scenario for this is the personal computing interactive environment. In this context, the standard keyboard and mouse (or equivalent) allow interaction with an almost limitless range of ‘interactive services’. Obviously a keyboard with around a hundred keys would generally not be considered appropriate for a living room environment. However, by far the most necessary aspect of the keyboard is rapid alpha/numeric input (ie typing and data entry), whilst most other input can be made via the keyboard or the mouse. The point here is that having a keyboard and a mouse is not necessary for all interactions, rather it is significantly more convenient. Thus, using a word processor with only a mouse would likely be very unpopular with most people, even though all the same tasks could be completed. On the other hand, many people would likely be quite happy to use drawing software with only a mouse (although those familiar with ‘short-cut’ keys may find a keyboard an important addition). In other words, careful consideration of all the input operations involved in all the services being offered, should help to indicate the most convenient ways for users to transmit that input. This convenience will generally be a trade off between the ‘simplicity’ of the device and the ‘simplicity’ of carrying out the interaction with that device. In general then, a service which can be designed so that all operations can be ‘point-and-click’ and is offered with a range of ‘point-and-click’ devices, would likely be convenient. However, a service (for example) offering access to ‘email’ would likely need an alpha/numeric keyboard to be considered convenient. In more specific terms, the interactive system evaluated by the present author (and referred to throughout this Style Guide) involved a wide range of services provided by a variety of different organisations. Mainly because it was a ‘pilot’ service no overarching ‘authority’ was in a position to consider all the services as a whole in the way outlined above. Thus, the handset provided with this system (described in earlier chapters) was something of a compromise with regard to ‘convenience’. This led in various ways to many of the difficulties the elderly volunteers experienced. However, all the required operations could be carried out (given suitable instructions) with this ‘universal’ handset. This was because a requirement for services to be included in the system was that the interactive software could interpret input of the type the specifications of the handset provided. Given a similar set of
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services with an overarching ‘authority’ it is possible that the handset itself may have been simplified. Beyond this, it is even more likely that carrying out the interaction tasks with the (possibly improved) ‘universal’ handset would have been more ‘convenient’ for the elderly volunteers. A very useful framework for considering the issues involved in matching differing system requirements with differing physical input devices is available, and anyone involved in this sort of decision is strongly urged to make full use of it134. Due to the commercial context in which such systems are produced there will likely be factors which will constrain the extent to which this aim can be realised. However, there is good reason to believe that aiming for an ‘inclusive’ approach will be more fruitful in opening up access to interactive services for more users than would an approach which provides only what product designers consider to be the control device for all users. This is particularly so in light of the impact of ‘the difference factor’ described in Chapter 453. It may well be, of course, that an interactive system effectively involves only a single service. In this case there is the possibility of providing a ‘specialised’ input device which is tailored precisely to the system and user requirements. A general example of this comes from another interactive system evaluated by the present author which has not been explicitly referred to in this Style Guide. In simple terms this service allows users to participate in various ‘quizzes’, either just against other members of their household, or against all other subscribers. Of the ‘quizzes’ involved, some are ‘stand-alone’ while others incorporate and are superimposed upon, broadcast television programmes. Thus, this service involves a ‘programme guide’ which indicates the broadcast and ‘stand-alone’ quizzes which can be interacted with, and when they are available, and this listing also gives direct access to them. The layout of this lends itself well to simple point-and-click input. In general, the ‘quizzes’ are constrained to (up to four) multiple choice responses which lends itself well to a set of response buttons. Accordingly, the handset provided with this system provides suitable methods (and appropriate instructions) for interaction in these different environments. That is to say, the handset can be comfortably held (horizontally) between the hands. Next to one hand is a ‘fan’ array of response buttons which (depending on user preference) can be operated by the thumb (ie with fingers under the handset, the thumb can ‘sweep’ over the button array) or by the fingers (some find it easier to turn their hand the other way so that each finger can be comfortably associated with a button). Next to the other hand was the pointand-click device, which in this case was a ‘mechanical’ touch pad. This was operated by placing a finger (or thumb) tip onto a concave ‘button’ attached to a lever arm (which transmitted information regarding the button’s position within a screen shaped recess) and moving it to the desired position. The associated ‘select’ button was over by the other hand, but spatially separated from the four response buttons. This button was further differentiated from the array by the fact that they were blue and oval shaped whereas the ‘select’
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button was round and grey, which matched (and thus helped relate it to) the touch pad ‘button’. In general, the elderly volunteers using this system liked this control device and had very few problems using it. Taken together, the above suggests that while there may well be many (and occasionally intractable) difficulties designing the ‘software’ aspects of interactive services to cater to the cognitive and perceptual requirements of older people, it is also apparent that the availability (or not) of suitable input devices will have a major impact on how ‘convenient’ (or not) users find the actual interaction to be.
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Chapter
8
guidelines
It has been mentioned in various contexts throughout this Style Guide that prescriptive guidelines regarding the design of interactive services for older people are not likely to be particularly helpful and may even prove to be misleading. Therefore, despite the heading of ‘guidelines’, this chapter can be more accurately characterised as presenting a list of brief summaries of the main issues that have been described in the preceding chapters. The following list will generally present these issues in the order of their appearance in the Style Guide. Page references will also be given for easy location of the associated detailed discussions.
Characteristics of older users •
Older eyes undergo a variety of changes with advanced age which tend to degrade the accuracy of the visual information transmitted to the central nervous system. (p. 6 to 8)
•
Older ears also undergo changes with advanced age which degrade the accuracy of the auditory information transmitted to the central nervous system. (p. 9 to 11)
•
Older people’s central nervous systems tend to be ‘slower’ at processing information received from the senses, which means that varying amounts of information can be effectively lost. (p. 8 and 9, 12 and 13)
•
Information that is not lost can be ‘altered’ by factors such as the expectations of the viewer or listener, given a certain context. (p. 14)
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•
If ‘slower’ processing in the central nervous system results in a loss of auditory information, the negative impact can be relatively greater (than for any loss of visual information) due to the transient nature of sound. (p. 13)
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In any given listening situation, older people tend to experience relatively greater difficulty hearing sound compared to younger ones. The extent of this ‘greater difficulty’ is markedly enlarged when listening to speech. (p. 13 to 15)
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Speech must be presented as clearly and accurately as possible, as any degradation (or additional noise) will have a further, disproportionately negative impact on older listeners. (p. 14 and 15, 59 and 60)
•
Regarding touch and manual dexterity, older people experience a wide diversity of age-related changes, leading to an equivalently wide diversity of ‘user requirements’. Such that in many contexts the elderly population cannot be considered an homogenous group. (p. 15 and 16, 27 and 28)
•
Older people tend to be relatively slower mentally than younger ones. Such ‘slowness’ will be most apparent in novel situations, but can be compensated for by experience in more familiar situations. (p. 18 to 20)
•
Older people can have difficulty ignoring irrelevant information. Therefore, care should be taken to present only information that is immediately pertinent to the task in hand. (p. 20 and 21)
•
Older people can find it difficult to switch their attention between different things. Perhaps most notable is switching visual attention between different locations. (p. 21 and 22)
•
Older people’s working memory tends to be relatively more ‘fragile’. Such that information may more easily be forgotten if concurrent mental demands require more resources. (p. 22 to 25)
•
Today’s older generation was not ‘brought up’ amongst electronic devices in the way more recent generations have been, which makes it more likely for them to be intimidated by the idea of using such equipment. (p. 28 to 31)
95
•
The intimidation older people can feel about using interactive services can generally be eliminated if they have an understanding of the personal benefits which they may obtain from them and a successful and generally positive early experience with using them. (p. 31 to 34)
96
Elements of design •
Text should be presented as large as is reasonably possible. (p. 38 to 40)
•
Text presented as single words generally only needs to be satisfactorily legible for older viewers. Whereas text presented for continuous reading needs to be relatively clearer than simply legible to ensure adequate understanding of the content and its inferences. (p. 40 to 42)
•
On-screen presentations should not be overfilled with information or otherwise ‘busy’. Ideally, a single screen should contain a single ‘message’ or a single ‘activity’. (p. 42 to 44)
•
The layout of a screen presentation should be designed to make what it has to offer easily understandable to the user. This may also involve the use of explicit instructions. (p. 44 and 45)
•
The ‘meaning’ of any explicit instructions used should be checked with ‘naive’ users. (p. 44)
•
Icons that are ‘meaningful’ are more beneficial than abstract or arbitrary ones (although the ‘meaningfulness’ should be previously established with users). (p. 44 to 46)
•
Designers of screen layouts and their elements, should consider using a simulated reduction of visual acuity to check the clarity of their design. (p. 46)
•
Various forms of ‘highlighting’ can be useful for drawing users’ attention to ‘important’ areas of the screen. But care is needed to ensure that the ‘highlight’ is suitable, given the context. (p. 46 to 48)
•
‘Highlighting’ (and ‘lowlighting’) can be useful for ‘guiding’ users through a sequence of operations (locations) on a screen. (p. 48 to 50)
•
Some interaction tasks that can fit onto one screen may be easier for older people to deal with as a succession of screens containing one operation (and possibly associated instructions) on each. (p. 50 to 52)
•
A variety of techniques can be used to constrain progress through an interaction task, which can also ‘guide’ users and will generally minimise errors. (p. 52 to 54)
97
•
It is vital that users are given the opportunity to notice any mistakes they do make and are given the ability to make appropriate corrections or alterations in as efficient a manner as possible. (p. 53 and 54)
•
If an on-screen ‘pointer’ is used it must be clearly visible to older users and easy to use accurately. (p. 54 to 58)
•
Visual ‘highlights’ and other ‘events’ can often be usefully augmented by sound, which ought to be ‘rich’ (ie not pure tones) and preferably ‘meaningful’. (p. 58 to 60)
•
Consider allowing a certain amount of personal customisation of some presentation characteristics. (p. 54)
•
When providing access to large ‘catalogues’ of items, careful consideration should be given to the overall suitability of ‘menu’, ‘keyword’ or other forms of search method. (p. 62 to 64)
•
Older users will find it helpful if they are given an (suitable) overview of any large body of information (including the ‘network’ they are navigating through). (p. 64 to 67)
•
Whenever possible relieve the burden on older people’s memory by providing equivalent information on-screen. (p. 68 to 72)
•
For inherently involved or complex interaction tasks, consider providing an ‘interactive demonstration’ to ‘train’ novice users and prepare them for ‘the real thing’. (However, every effort should have already been made to ensure that the interactive service is effectively ‘walk-up-and-use’ regardless of the level of ability or knowledge of the user.) (p. 70)
•
All effort should be made to ensure that the presentation of interactive services and the operations involved in using them throughout a particular system, are as consistent as possible from the user’s point of view. (p. 74)
•
Give very careful consideration to the control device intended for use with the system, on the basis of easy use by all users (given the operations required of it). (p. 76 to 79)
•
Consider the benefits of providing a range of different control devices which are all equally compatible with the system. (p. 79 to 84)
98
Finally •
Consider the older user (you may be one yourself in the future).
99
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