Text entry on handheld computers by older users - Semantic Scholar

E RG ONOMICS, 2000,

VOL .

43,

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6, 702±716

Text entry on handheld computers by older users P ATRICIA W R IG HT ² *, C H RISTIN E BAR TRAM ³ , N ICK R OGERS³ , H AZEL E MSLIE³ , J ONATHAN E VANS³ , BARBARA W ILSON ³ and STEVE BELT² ² School of Psychology, Cardi U niversity, Cardi CF 1 3YG , UK ³ M RC Cognition and Brain Sciences U nit, Addenbrooke’s H ospital, Cambridge,

UK Keywords: M obile computing; H andheld computers; Older users; Touch-screens; Pen computing; D ata entry. Small pocket computers o er great potential in workplaces where mobility is needed to collect data or access reference information while carrying out tasks such as maintenance or customer support. This paper reports on three studies examining the hypothesis that data entry by older workers is easier when the pocket computer has a physical keyboard, albeit a small one, rather than a touchscreen keyboard. U sing a counter-balanced, within-subjects design the accuracy and speed with which adults over 55 years of age could make or modify short text entries was measured for both kinds of pocket computer. The keyboard computer was the H ewlett Packard 360L X (H P), but the touch-screen computers varied across studies (experiment 1: Apple Newton [ and PalmPilot [ ; experiment 2: Philips Nino [ ; experiment 3: Casio E10[ ). All studies showed signi® cant decrements in accuracy and speed when entering text via the touch-screen. Across studies, most participants preferred using the H P’s small physical keyboard. Even after additional practice with the touch screen (experiments 2 and 3) many entries still contained errors. Experiment 3 showed that younger people were faster but not more accurate than older people at using the touch-screen keyboard. It is concluded that satisfactory text entry on palm-size computers awaits improvements to the touch-screen keyboard or alternative input methods such as handwriting or voice. Interface developments that assist older people typically bene® t younger users too.

1. Introduction The range of ergonomics problems that arise from `ubiquitous computing’ have recently been highlighted by Baber et al. (1998). Issues relating to data input are among these. Although studies of alternative ways of inputting information into computers have a long history (for a review of many of these options, see G reenstein and Arnaut 1988), technological advances supporting mobile computing have given fresh impetus to circumventing the constraints of working with small handheld computers (K awachiya and Ishikawa 1998, M asui 1998). N umerous pocket and palm-size computers are commercially available. In September 1999 the magazine HandHeld PC listed 17 companies making devices for the Windows CE operating system (Anon 1999). Between them these companies o ered 15 handheld pocket-size machines with a small physical keyboard, and 11 palm-size computers having only a

*Author for correspondence. e-mail: WrightP1@cardi .ac.uk Ergonomics ISSN 0014-013 9 print/ISSN 1366-584 7 onlin e Ó 2000 Taylor & F rancis Ltd http://www.tandf.co.uk/journals

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touch screen. Omitting the keyboard reduces the size of the computer and makes it lighter to carry. F or text entry a keyboard can be displayed on the touch-screen and this is tapped with a plastic stylus. This stylus is often referred to as a pen and so this method of text entry via a touch-screen keyboard is called pen-based computing (M illen 1993, M eyer 1995). Both kinds of handheld computer are available for several operating systems and the use of handheld computers both inside and outside the workplace is growing. The focus of this paper is to explore the relative adequacy of these two kinds of handheld computer for tasks involving short data entries. It is not being suggested that these small computers are suitable for extensive text entry since even large touch-screens are known to be error prone (Plaisant and Sears 1992). N evertheless some advocates of pen-based computing have suggested that text editing bene® ts from enabling simple gestures, such as a horizontal line or oblique stroke, to accomplish commonly used text editing functions such as delete (N oro 1995). The keyboards on handheld computers are usually too small for conventional touch typing, so they may not be more useful than the touch-screen alternatives. M oreover if held in the hand this precludes touch typing skills. So the question arises as to whether a physical keyboard will be more e ective for handheld computers than the touch-screen alternatives. Although the intended market for these small computers may primarily be the business community (Whittle 1998) there is already evidence that they are being found useful in other work contexts including sheep farming and technical fault ® nding (Lewis and D avies 1998). H andheld computers o er a range of applications but their ability to provide auditory and visual reminders enables them to serve as memory aids. These not only assist busy people but can be a lifeline for those with memory problems arising either from the ageing process (Smith and Earles 1996) or from brain injury (Wright et al. 2000). Support from mobile computers could help people with memory problems to remain employed or maintain their independence if retired. F or those who are unfamiliar with computers, especially older people, the absence of a keyboard may be an advantage because keyboards with their numerous dedicated function keys can look daunting. While making any computer suitable for older people may require changes to the interface (M orris 1994), handheld computers may need sophisticated design to compensate for visual impairments or di culty with the ® ne motor control needed to use the touch-screen keyboard (Panek 1997, Czaja 1988, Wright 1999). It has been shown that even domestic products such as microwaves that have touch-screens can be more easily used by older people if redesigned (Loring 1995). Three of the problems associated with the use of keyboards displayed on small touch-screens include modedness, size and feedback. (1) Modedness. The space available on the screen is very small so that the keyboard often requires the use of special function keys to access certain numeric and punctuation characters. It has long been known that moded styles of interaction can be confusing for users (Tesler 1981, Smith et al. 1982). (2) Key size. Studies of performance with normal size keyboards have shown that although older people are slower in key tapping and in selecting the key to tap (Salthouse 1984), especially if they are unskilled typists (Bosman 1994)

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P. W right et al. there is no loss of accuracy. G iven su cient experience with the task there is evidence that older people may be able to use compensatory strategies to maintain their performance (Salthouse 1987, Bosman and Charness 1996). H owever, with palm-size computers the limited screen width means that when displaying the QWER TY keyboard on screen, the space available for each key is very small. This will slow performance (Sears et al. 1991) and may also give rise to legibility problems with di culty in discriminating between some letters such as `u’ and `v’ . The lack of space also results in a lack of any gap between adjacent keys. This necessitates ® ne motor control by those making text entries. The theory underlying keyboard movements has been well articulated (D rury and H o man 1992) and task analyses of typing skills o er a powerful account of the performance of older users (Salthouse 1984, 1986). H owever, tapping the keys on a touch-screen is not a highly learned skill. M oreover, empirical evidence supports the recommendation that the gap between keys should correspond to the width of the tapping device, whether ® nger or pen (H o man et al. 1995), but the allocation of such interkey space on the screens of palm-size computers would involve reducing the size of the keys themselves, which would further impair legibility. (3) Feedback. With both kinds of pocket computer the skill of touch typing is not an option, and because writers are looking at the keyboard while tapping keys, errors of text entry may not be noticed. Such errors may be more common with touch-screen keyboards because they can easily arise from the pressure needed to activate a key (Logan 1985). F or example, if too much pressure is applied or for too long then a tap on the screen can be misinterpreted by the computer as a double or triple tap. The tactile feedback received when activating a physical key makes such errors less likely to occur. Touch-screens also require calibration so that they respond appropriately to the angle of contact that the pen makes with the screen. This in turn means that users need to maintain a fairly consistent writing angle, so creating another opportunity for error that is not present with the physical keyboard.

All three of these drawbacks of touch-screen keyboards may be exacerbated by the e ects of age. Consequently the participation of older people in these studies can serve as a magnifying glass for examining the problems of using palm-size devices with touch screens. One practical consequence of these studies could be evidence that older people ® nd it more satisfactory to use the bulkier handheld machines that have a keyboard rather than the smaller pen-based machines. In this respect the participation of older people may indicate one important design boundary for developments in mobile computing, a boundary that is growing in importance with the convergence of the technologies of mobile phones and handheld computers. The following studies examine the performance and preference of older people when using handheld computers to make short text entries, such as might be made with a personal organiser or when ® lling in an electronic form. 2. Method 2.1. Design There were two independent groups, di ering in which pen-based computer they were given. F or each group a within-subjects design was used in which all participants worked with both the H ewlett Packard 360/LX and a pen-based

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computer in counter-balanced order to edit text on the computer. F or one group the pen-based computer was the Apple N ewton [ and for the other group it was the 3Com PalmPilot [ . The main measures were accuracy and speed of input, together with preference for input method. 2.2. Procedure Before using either computer a variety of measures were taken that would allow analysis of likely predictors of performance if only some people found the pen-based computer di cult to use. An interview assessed factors likely to in¯ uence their performance, such as their experience with computers and other forms of technology. As a performance measure of keyboard dexterity, participants completed ® ve arithmetic additions using a small pocket calculator. These additions were presented simultaneously on a card and participants spoke the total that they had reached for each sum. R esponse times and accuracy were recorded. This task was presented to participants as an evaluation of the ease of using a small calculator keyboard. The green numbers of the calculator’s LED display a orded a contrast with which the LCD displays of the small computers could later be compared. Visual acuity was assessed using a form of the Lighthouse N ear Visual Acuity Test [ (2nd edition) in which people read as far down the chart as they could. They were also asked to select the print size that they felt would be most comfortable when reading. 2.3. T ext entry The experimenter read a short phrase, typical of diary appointments, and participants entered this into a horizontal slot that simulated the space available in a template form being completed or in a diary or scheduler. This task had the advantage of being readily understood by the participants, and also being similar to short text entries that might be made in work contexts where handheld computers were being used to collect data or issue search commands to a database. Before using each computer, participants underwent a brief training in four basic text entry functions. They practised moving the cursor, text entry via the physical or touchscreen keyboard, use of the space bar and the delete key. This introduction was followed by 11 timed text entry trials for which the experimenter either spoke the phrase to be entered, or the text was already on the screen and participants were asked to modify it in speci® c ways. When changes were required, printed cards showed the text to be inserted printed in red and the remaining text in black. Participants were asked not to correct any errors made. The time comparisons reported below are conservative, being shorter than they would be if people corrected errors in actual usage. This constraint seemed desirable since tapping the small touch-screen keyboard might encourage participants to sacri® ce accuracy for speed, and relatively separate measures of speed of text entry and accuracy would reveal this. 2.4. Attitude ratings After the text input trials, participants made four ratings each on the scale from 1 ± 10 for the adequacy of: (a) the size of the letters on the screen; (b) colour of the letters on the screen; (c) the keyboard; and (d) the computer’s overall ease of use on text entry. After using the second computer and completing the attitude ratings, participants indicated their preference between the computers and the likelihood that they would use either computer if they won it in a competition.

706

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3. Experiment 1: keyboard vs touch-screen 3.1. Materials The keyboard machine was the H ewlett Packard 360LX. This was chosen because its keyboard characteristics were in the mid-range for such machines. The keys were labelled very legibly and were separated from each other by physical space, but they did not o er the scope for touch typing that some handheld computers aspire to (e.g. the Psion Series 5). The H P also has a touch screen and a stylus but this was not used in the present experiment. One pen computer was the Apple N ewton 100, chosen because it was similar in size and weight to the keyboard machine and so any di erences obtained would relate to the di erences in method of input rather than overall di erences in physical characteristics. H owever, the bulk and weight of the Apple N ewton might make it unrepresentative of the range of small pen-based computers. So the other pen-based computer was the PalmPilot [ manufactured by 3Com, which at the time of data collection was the market leader in the ® eld of pen-based personal digital assistants (Orlowski 1999). It can easily be held in the hand and therefore it o ers more scope for readers to adjust the angle of view to maximize legibility (Schultz 1998). M oreover it is known that people reduce their viewing distance for handheld displays, compared with viewing screens on the o ce desk (Trautman et al. 1995). Enhanced legibility together with any changes in the sensitivity of the touch-screen may reduce errors when entering text. On the other hand the stability o ered by using the heavier pen-based machine on a table top may give more accurate performance. 3.2. Participants Sixteen volunteers from the panel of the M edical R esearch Council (M R C) Cognition and Brain Sciences U nit in Cambridge were paid for taking part. Eight volunteers used the Apple N ewton 100, 3 men and 5 women. Their mean age was 62 years (SD = 4.6 years, range = 57 ±68 years). Eight volunteers used the PalmPilot, 4 men and 4 women. Their mean age was 62 years (SD = 5.3 years, range = 59 ±69 years). 3.3. Results 3.3.1. Accuracy: The error frequencies for both groups with each machine are shown in table 1. Pooling across both groups, 15 people made more errors with the pen-based computer than with the keyboard machine (N = 15, x = 0, p < 0.01). One person in the PalmPilot group made more errors with the keyboard. The errors were not con® ned to particular text entries. Comparison of the same phrases being entered on both machines con® rmed that pen input was more error-prone (Apple N ewton group: Wilcoxon T = 4.5, p < 0.01; PalmPilot group: Wilcoxon T = 2, p < 0.02). The most common error was to omit spacing between words, and the computers did not di er in the frequency of these errors (pen = 23 [13+ 10], keyboard = 18 [10+ 8]). Such errors may re¯ ect the unfamiliarity of these participants with the use of keyboards. In contrast, errors resulting from wrong pressure (e.g. double letters) were more common with pen input (13+ 2) than with the keyboard (1+ 0). So too were errors from tapping the wrong letter (Apple N ewton 7, PalmPilot 19, keyboard = 0 and 3 from the Apple N ewton and PalmPilot groups, respectively). These mistakes may indicate di culties in visually discriminating among certain letters on the touch-screen keyboard.

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3.3.2. T imes: It might have been the case that people made errors with pen input because the interface enticed them to tap quickly. H owever, the mean time per trial was signi® cantly longer with the pen (Apple N ewton group: pen = 21.5 s, SD = 2.7; keyboard = 15.8 s, SD = 2.9; Student’ s t = 2.56, df = 7, p < 0.05; PalmPilot group: pen = 18.8 s, SD = 5.3; keyboard = 14.0 s, SD = 2.9; Student’s t = 2.42, df = 7, p < 0.05). This pattern of pen input being slower remained even when the analysis was con® ned to trials on which there was a low error rate. 3.3.3. Attitudes: Asked to say which computer they preferred, 15 people chose the H P. Only one person, in the Apple N ewton group, chose the pen-based machine. Pooling across the four ratings given to each computer immediately after using it (maximum score = 40) showed that 15 participants gave higher ratings to the keyboard (mean = 31.6) than the pen computer (mean = 23.1), indicating a more positive attitude towards keyboard entry (table 2). This was also evident in the frequency of ratings below the mid score of 5 for each feature rated. Only two people gave such a low rating to the H P whereas 10 people (5 in each group) gave low ratings to pen input, mostly for the keyboard and overall ease of use. Table 2 shows that the discrepancy in attitude to the computers existed for all characteristics rated and in both groups. When asked if their attitude towards computers had changed as a result of using these computers, 12 people gave a rating (out of 10) that was 7 or higher, indicating strong positive change (7 in the Apple N ewton group, 5 in the PalmPilot group). Similarly many comments during the interview period after using both computers re¯ ected a positive change in attitude towards small computers. N evertheless, when asked if they would personally use computers such as these if they won one in a competition, 5 people (4 from the Apple

Table 1.

Errors with the keyboard and pen-based computers in experiment 1.

Group using speci® c pen-based computer

Errors with the pen-based computer

Errors with the keyboard computer (HP)

Keyboard advantage

32 27 59

11 11 22

21 16 37

Apple Newton PalmPilot Total errors

Table 2.

M arks out of 10 for interface features in experiment 1 (higher values= better). Apple Newton group

F eatures Letter size Letter colour Keyboard Ease of use Total

PalmPilot group

Pen-based

Keyboard

Pen-based

Keyboard

7.9 7.0 4.6 5.3 24.8

7.6 8.0 8.4 8.5 32.5

6.1 6.1 3.8 5.3 21.3

7.5 7.1 8.1 8.1 30.8

708

P. W right et al.

N ewton group) said `N o’. This answer may have been speci® cally coloured by the task context of diary entries since many of these participants felt that they had no personal need for a computer-based diary. The auditory alarm was of no bene® t since most of their personal reminders had a wide time frame (e.g. buying a birthday card). In the terminology of Ellis (1988) their prospective events were steps rather than pulses. If the task had been presented as a di erent computer application, perhaps one having database characteristics, then the apparent contradiction between people’s increase in positive attitude to computers and the perceived personal usefulness of these handheld devices might have not arisen. 4. Experiment 2: extended practice 4.1. Materials The ® ndings of experiment 1 showed that the problems of text input to pen-based computers are not speci® c to one machine. H owever the amount of practice in experiment 1 may not have been su cient. It is possible that the errors would disappear as people become more familiar with the characteristics of touch-screen keyboards. This possibility was examined in experiment 2 and the opportunity was taken to extend the comparison to a third pen-based computer, the Philips N ino [ , this being the ® rst of the commercially available Windows CE palm-size computers in Britain. The procedure for the ® rst part (phase 1) of experiment 2 was identical to the previous experiment. In the second part (phase 2) of experiment 2, participants entered 24 short phrases in two sets of 12 phrases with a 10-min interval between sets. Each phrase was read and entered before the next phrase was read, and the interval between sets was ® lled with a discussion of computer facilities such as voice annotation. The two sets of phrases were matched for length (51 characters) and included similar frequencies of those letters that had been found to be most troublesome in the previous experiment. 4.2. Participants Two men and six women from the same volunteer panel as in the previous studies were paid for taking part. Their mean age was 52.8 years (range = 56 ±68 years, SD = 4.4 years). 4.3. Results 4.3.1. Accuracy and times during phase 1: An analysis of the ® rst part of the experiment enables comparison with experiment 1. N early twice as many errors were made with the pen-based computer (27) as with the keyboard machine (15) (Wilcoxon T = 3.5, p < 0.05), which replicates the previous ® ndings. Similarly text entry was signi® cantly faster with the keyboard machine (12.2 s) than with the penbased computer (15.7 s) (Student’s t = 2.93, df = 7, p < 0.05). 4.3.2. Practice in phase 2: In order to gain insight into the e ects of additional practice, the data were contrasted for the ® rst and second sets of 12 entries. It was found that everyone made more completely accurate entries during the second set of phrases (mean 7.5 accurate = 63% ) than during the ® rst set (mean 4.6 accurate = 38% ) (Student’s t = 4.71, df = 7, p < 0.01). The total number of errors also dropped signi® cantly in the second set (total errors of ® rst set = 13.9, second set = 8.3; Wilcoxon T = 0, p < 0.01). H owever, the accuracy level remained

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disappointing. D uring the second set of entries, errors were made on every trial by at least one participant and no-one achieved 9 entries (75% ) without error. Although six of the eight participants improved in speed for the second set of phrases this was not statistically signi® cant (Student’s t < 1, ns). This lack of improvement in speed is further evidence that the problems of entering text into pen-based computers do not rapidly disappear with practice. These practice data are summarized in table 3. Of course it is possible that even greater practice would have been bene® cial, but even when the analysis is con® ned to the last three trials no-one entered all three phrases correctly. The mean number of errors per trial was 7.3 and the mean number of people making an error was 4 people per trial (i.e. 50% participants). 4.3.3. Attitudes: As in experiment 1 everyone preferred the keyboard computer (N = 8, x = 0, p < 0.05) and pooling across the four sets of ratings everyone gave it higher marks (30.4) than the pen-based computer (17.1) (N = 8, x = 0, p < 0.05). The mean ratings on each of the four features are shown in table 4 where the biggest di erence was on the rating of the keyboard. As in experiment 1, several participants (6) said that they would not use computers such as these if they won one in a competition. It is possible that the problems of text input with pen-based computers that have been observed in these two experiments are not speci® c to older people. They may hamper people of any age when doing text entry. To check this possibility the procedure of experiment 2, with its extended practice, was repeated for participants from three age groups in experiment 3.

5. Experiment 3: e€ ects of age 5.1. Materials The test materials and two data collection phases remained unchanged from experiment 2 but the opportunity was taken to extend the comparison to one more

Table 3.

E ect of practice on accuracy and speed with pen-based input in experiment 2. Accurate entries (Max= 12)

Order of phrases F irst set Second set Table 4.

Characters wrong per person

M ean times (s)

M ean

%

13.9 8.3

2.93 2.91

4.6 6.5

38 54

M arks out of 10 for interface features in experiment 2 (higher values= better).

F eatures Letter size Letter colour Keyboard Overall ease of use Total

Pen-based computer (HP)

K eyboard computer (Nino)

K eyboard advantage

4.0 4.9 3.6 4.6 17.1

7.5 6.4 8.4 8.1 30.4

3.5 2.5 4.8 3.6 14.4

P. W right et al.

710

pen-based computer, the Casio E10. The machine had the appearance of being smaller and lighter than the N ino, although the actual di erence in physical characteristics was slight. The data were collected in a 2 h session involving several other experiments unrelated to handheld computers. One consequence of this was that the interval between sets 1 and 2 of the extended practice lasted 20 min rather than 10 min. Since the main purpose of experiment 3 was the comparison across age groups, not a comparison with the N ino, it was felt that this increased interval would heighten rather than reduce the di erences between younger and older participants. 5.2. Participants Twenty-four participants from the volunteer panel of the M R C H ealthcare Information Project at Cardi U niversity were paid for taking part. They came from three age bands that were designated Younger (18 ±25 years, mean age = 20.4 years, SD = 1.1 year); M id (35 ±45 years, mean age = 38.6 years, SD = 3.9 years), and Older (55 ±65 years, mean age = 60 years, SD = 2.9 years). There were four men and four women in each age group. 5.3. Results 5.3.1. Accuracy and times during phase 1: Table 5 summarizes the errors made on each computer by those in di erent age groups. On average all groups made more errors with pen input than when using the keyboard machine (pooling across age groups, Sign test N = 19, x = 4, p < 0.02). Of the four people who made more errors with the keyboard, two were in the M id group and two in the Older age group. Although table 5 suggests that age had less e ect on accuracy of using the pen-based computer no comparisons were statistically signi® cant (M ann-Whitney tests, p > 0.5). On average all age groups were slower using the Casio (Sign test N = 24, x = 4, p < 0.01), with the four exceptions spanning the age range (one person from each age group and two from the Older group). Pooling across computers showed the expected trend of accuracy and speed decreasing with age (table 5). H owever, the di erence in times between the age groups was signi® cant only for the comparison of Younger and Older, where it was signi® cant for each computer (F isher-Yates Exact tests, p < 0.05). Analysis of the di erence in time taken by people when using the two computers showed no e ect of age (F < 1). These accuracy and time data suggest that the performance impairment associated with the pen-based computer was no greater for the Older group than for those in the Younger group.

Table 5.

Performance on both computers in experiment 3.

Entries wrong (max= 13) Age group Younger M id Older M ean

M ean times (s)

Pen-based

Keyboard

Total

Pen-based

K eyboard

Total

2.4 2.5 2.8 2.6

1.1 1.8 2.1 1.7

3.5 4.3 4.9

1.1 1.3 2.1 1.3

0.8 1.1 1.4 1.1

1.9 2.4 3.0

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5.3.2. Attitudes: Table 6 summarizes the ratings given to each computer. As in both previous experiments the keyboard machine received higher ratings, but across the three groups the column totals in table 6 show that the preference for the keyboard machine grew stronger with age (mean di erence between H P and Casio was: Younger = 1.4, M id = 6.3, Older = 8.4). Table 6 also shows (ratings for K eyboard and Ease of use) that the pen-based input was not as irksome to the Younger group as to the other groups. This more positive attitude to the pen-based computer was also evident in participants’ answers when asked which computer they preferred. All of the Older group preferred the H P, as did seven people in the M id group, but only four of the Younger group. This may be related to people’s estimate of the personal usefulness of the machines. When asked whether they would use a computer such as one of these if they won one, all eight in the Younger group said `yes’, whereas only four in the M id group and ® ve in the Older group said `yes’. 5.3.3. Practice in phase 2: The aim of experiment 3 was to see if di culties in using the touch-screen keyboard would disappear with practice at a similar rate for all age groups. The e ects of practice are summarized in table 7 where it can be seen that in the second set of phrases more than one-third of diary entries were wrong for all age groups. This set of entries showed no age-related di erences in the number of accurate entries but the Younger group were signi® cantly faster than each of the other two groups (F isher-Yates tests p < 0.05). This is consistent with the ® ndings of H artley et al. (1984) who used normal keyboards and reported that after 12 h of practice on a word-processing task the main di erence between younger participants (18 ±30 years) and older participants (65 ±75 years) was the time taken to complete tasks. As in experiment 2, performance remained error-prone even on the last three phrases entered, where 83% of participants made errors. Of the four people who

Table 6.

M arks out of 10 for interface features in experiment 3 (higher values= better). Pen-based computer (HP)

Letter size Letter colour Keyboard Ease of use Total

Table 7.

Younger

M id

Older

Younger

M id

Older

5.5 6.8 6.0 6.1 24.4

5.9 6.5 5.0 4.6 22.0

5.5 5.6 5.0 5.6 21.7

5.4 7.0 6.4 7.0 25.8

6.3 7.0 7.6 7.4 28.3

6.9 7.6 7.7 7.9 30.1

E ect of practice on accuracy and speed with pen-based input in experiment 3. Characters wrong

Age group Younger M id Older M ean

K eyboard computer (Casio)

M ean times (s)

Accurate entries (max = 12)

1st set

2nd set

1st set

2nd set

1st set

2nd set

6.5 5.1 2.4 4.7

9.9 6.8 6.0 7.5

2.2 4.0 5.0 3.7

4.5 7.7 8.1 6.7

7.4 7.7 10.0 8.4

6.7 7.4 7.5 7.0

P. W right et al.

712

made no errors, one came from each age group and two came from the M id group. On the ® rst set of phrases the Older group were signi® cantly more accurate than the M id group (F isher-Yates p < 0.05). Others have reported that older people are more likely to emphasize accuracy than younger people (Salthouse 1979); however, comparison with the data from experiment 2 (table 3) shows that all age groups were more accurate than participants in experiment 2, particularly the Older group who were of a similar age in both experiments. The most likely cause for this di erence is that the preceding activity in experiment 3, making judgements about risk, in¯ uenced the speed-accuracy trade-o people adopted in the direction of making accuracy more salient. This was a transient e ect and by the second set of phrases performance was comparable in experiments 2 and 3. H owever, this does highlight the possibility that people could be encouraged to be more accurate with pen-based entry in some working contexts. The similarity in performance on the second set of phrases between experiments 2 and 3 would mean that it is essentially the di erence on the ® rst set that needs accounting for. N evertheless the task occupying the gap between the sets of phrases may also have contributed to the performance decrement observed for all age groups between these sets, instead of the increment observed in experiment 2. In experiment 2 this task, although not involving keying data, remained focused on the topic of handheld computers, whereas in experiment 3 the interval was 10 min longer and involved rating the informativeness of video clips that had no relation to handheld computers. This longer task may have been more demanding and participants may have felt more tired by the second set of phrases. If so, the patterns in these data may be a fairer re¯ ection of performance during a working day than those of experiment 2. Yet in spite of di ering slightly from the patterns found in experiment 2, these data from experiment 3 show that problems with accuracy in using pen-based computers are not con® ned to Older people and do not disappear with the amount of practice given here. People could make more than one kind of error on a trial, so for ease of comparison the summaries shown in table 8 pool across the 24 phrases entered in phase 2 to give the percentages of trials within each age group where errors of a speci® c kind were made (i.e. each percentage is based on a maximum error of 24N = 192). Table 8 shows that the pattern of errors was very similar across age groups with the most frequent mistake being to mis-key a character, i.e. entering a letter from a keyboard location close to the target key (e.g. typing `ib’ for `in’). The next most frequent category of errors arose from using the wrong pressure. This resulted in text with the wrong number of double letters (e.g. `boook’). Some of these mistakes (e.g. only one p in appointment) may have been spelling errors that also occurred with words such

Table 8. Age group Younger M id Older M ean

Percentage trials during practice in experiment 3 on which speci® c kinds of errors were made. M is-keying

Wrong pressure

Spelling

24.5 17.2 10.9 17.5

19.3 10.4 8.8 12.8

5.2 5.7 3.1 4.7

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as lasagne and even `docter’ and `tennice’. The use of auditory presentation rather than a copy typing task gave rise to a fuzzy border between the pressure and spelling categories. N evertheless table 8 shows that tapping the right key and doing so with appropriate pressure were the main causes of errors with the touch-screen keyboard. 6. General discussion Across all three studies people overwhelmingly (88% ) preferred using the small computer keyboard to pen-based input. The question therefore arises as to whether pen-based computers are worth considering further. The big advantage of the penbased device is its portability. It is lightweight and easily slips into a pocket. The present studies were all conducted in a single location where portability was not an issue. The pen-based computer was more acceptable to the younger age group and this may have been because they could envisage themselves carrying it around. (F our of the Younger group said that they would use the pen-based device if they won it.) Other factors in the workplace may in¯ uence the trade-o s people make when expressing a preference between these two kinds of computers. In a clinical study where 12 people with memory problems used the Casio and the H P for successive, counterbalanced 2-month periods, they were asked at the end of the second period which machine they would want to retain if they could keep only one. Seven participants chose the Casio, two people had no preference and only three people preferred the H P (Wright et al. 2000). F or personal diary entries the accuracy of the typing may not matter since the meaning of the entry often remains clear. N evertheless these ® ndings indicate that the touch-screen keyboards of pen-based pocket computers are not ideal for alphanumeric entries, even when the text is limited to short phrases such as diary appointments. It therefore seems essential to explore alternative input methods. One design alternative that addresses the problem of pressure errors is for letters to be selected by removing the pen from the screen rather than by tapping. G iven that more than a decade ago Potter et al. (1988) found that this method of text entry improved accuracy it may seem surprising that none of the commercial palm-size computers with touch-screens has adopted this style of interaction, or even o ers users the option. H owever it was found to be slower than tapping and might become more error prone in working environments where people need to use both desktop and handheld machines. A compromise might be worth exploring where light contact between pen and screen highlights the key beneath the pen, but ® rmer pressure is needed for selection. Intelligent software that prompts users with possible words has been found to be helpful in some contexts (M asui 1998) and might be well suited to constrained work environments such as warehouse stock control. Where text entries are short, this reduces the contextual information that intelligent software will use to o er word choices, and so other design options are needed. Software that enables voice commands to be issued to pocket computers is commercially available and there is evidence that combining voice and touch-screen can be successful in work environments where issuing commands is the main task (N akagawa et al. 1995). H owever, this does not o er a solution for tasks requiring the entry of alphanumeric text.

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Voice annotation is already available on several pocket computers allowing speech to be captured and played back later as in a dictaphone. While this may circumvent problems of input, it can lead to retrieval problems if many annotations are made. Attaching text labels to the voice annotations reduces these retrieval problems but creating the text labels may require a touch-screen keyboard. Speechto-text software is becoming more sophisticated and could potentially o er an attractive solution but is not yet available on pocket computers and even on desk top machines the software usually requires a headset with microphone attached, which can reduce its usefulness in some contexts of mobile computing. Several handwriting recognition systems are available for pocket computers (e.g. Calligrapher [ , G ra ti[ , Jot [ ). These di er in the amount of learning they require by the user and the amount of training needed by the computer. H andwriting may o er a viable solution in the longer term, but in some preliminary studies with Calligrapher, which interprets cursive script without special training, the authors have found that accuracy was no higher than with the touch-screen keyboard, and the study was abandoned when it was seen that phrases selected for input were critical determinants of the apparent accuracy of the software. Choosing not to convert the handwriting but leaving it as a bit-mapped `inky note’ has the twin disadvantages that such handwriting needs to be large to be legible, and computer-based tools for searching and sorting cannot be applied to the information. Therefore pen-based computers may be most useful when providing information to be read rather than when entering text. The writing could be done by docking with another computer, either laptop or desktop. This is the solution adopted by credit-card sized computers such as the R ex[ . Another solution is to link the pen-based computer to a physical keyboard when wanting to write, which was the solution adopted by Apple for the N ewton [ . H owever, this solution is feasible only where data entry is done in intermittent phases (e.g. at the beginning or end of a work period), not where it is interspersed throughout the day. There is evidence that adding non-speech sounds can enhance the usability of numerical keypads on small computer touch-screens (Brewster and Cryer 1999) but the acceptability of a noisier keyboard may depend on the working environment. Another possibility is to improve the touch-screen keyboard itself. Improvements to the size and font of the letters may await technical advances in screen resolution, but other possibilities include individual keys that zoom larger as the stylus hovers over them thereby enhancing legibility and o ering a larger target for the pen. The ® ndings from the present studies suggest that there is an urgent need to ® nd an accurate means for entering text into the pen-based computers if they are going to be useful in the workplace for those who do not have access to other computers. One by-product from these studies concerns the data entry task used. Although accurate text entry was a problem, mastering the task was not. Pocket computers can be simple to use and highly informative reminding devices, and as such could o er useful support to older people at work and elsewhere. Of the 32 older participants in these studies, 16 (50% ) said that they would personally use a small computer such as this if they won one in a competition. This is counter-evidence to the claims that older people have no interest in information technology and supports other evidence that many older people can acquire new complex skills, they just take a little longer than younger people (R abbitt 1997). H owever, before computers relying on touchscreens can adequately serve the needs of older people inside and outside the workplace, design solutions to the problems of accurate text entry are required.

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Acknowledgements This study was made possible by grant PCD 2/A1/215 from the N H S N ational R &D Programme for People with Physical and Complex D isabilities. The authors would like to express their thanks to Professor William M arslen-Wilson for permitting access to the volunteer panel of the M R C Cognition and Brain Sciences U nit, and a very special thanks to Sue Allison for so helpfully facilitating access to older participants. The authors are also grateful to Elizabeth Caddy for turning thoughts on tape into words on paper and to H ilary Williams for assistance with data analysis. References

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