on the screen, they read laboriously. Reading is facilitated by appropriate .... Reading (Massachusetts),. 1992. Van Nes, F.L., Juola, J.F. and Moonen, R.J.A.M.,.
Screen Usability Guidelines for Persons with Disabilities Monique Noirhomme-Fraiturel, Facult&
Universitaires
Notre-Dame
Jean M. Vanderdonckt2 de la Paix, Institut dhformatique
Rue Grandgagnage, 21, B-5000 Namur (Belgium). Fax. : +32 (0)81-72.49.67 - Telex :59.222 FacNamB leMail 2eMail
: MN01~OM~@l~0.~~PoAC6BE
. Telc : +32 (())8 1.72.49.79
: JVA~E~ONCKT@~Oo~~PoA~,BE
- Tel+ : +32 (0)81.72.49675
ABSTRACT
This paper presents lessons learned from implementing interactive applications for adults persons with moderate mental disabilities.
Guidelines
lity have been drawned plementing
for improving
screen usabi-
from the experience gained in im-
and using such softwares.
KEYWORDS: Analysis and Evaluation Techniques, Guidelines, Persons with Disabilities, Software Ergonomics, Usability Testing. INTRODUCTION Many studies have been achieved Machine gonomics,
Interaction cognitive
in the field
human factors and from
the
technical point of view of specifying, designing and automatically generating user-interface. These works deal mostly with interactive applications which are appropriate to valid persons: office automation applications, word processing, spreadsheet,.. .Unfortunatel y, few has been already said for Motor Cerebral Disabled (MCD) persons and for mentally handicapped one. Such interactive applications have been implemented sity of Namur,
as a collaborative
Swiss Federation
work of Univer-
of Telethesis
capped vision
[2]. Moreover,
when they are able to read
something on the screen, they read laboriously. Reading is facilitated by appropriate enlarged characters size. This aspect is not obvious when implementing applications with HyperCard@ or Ms-WindowsT~: the standard matrix of menu items and icons are too narrow to be legible. Magnifying characters size reduces the screen capacity so that same information must be spread on different screens.
of Man-
from the point of view of software ermodels,
Chamcters size should be appropriate to vision disability. Choosing the right typogmphy is an acute problem not only for normat users but also for many persons with handi-
and MCD
specialized service in Pediatrics Department of H6pital de Bic~tre. These applications help the person with disabilities in common daily tasks (home banking, menu management) or have educative goals (knowledge of human body, graphical expression, puppet-show game) [3]. SCREEN USABILITY GUIDELINES Eight kinds of guidelines emergd to be fundamental
when
designing screens usable for persons with disabilities. Some of these guidelines have already been introduced by different authors [1,2,6,7]. The aim is to tailor these guidelines for persons with mental disabilities and to render them more explicit.
Provide high quality graphics Sometimes black and white graphics with high quality
grey
shades are more legible than a too colourful illustration. Such graphics we also preferred for technical reasons: coIour display devices do not render all the colours as intended by the graphical expert and freehand drawings are not imported in the software as equally as well. Icons can be abstract and are preferable than too complex digitalized images. Guidelines about icons [1,2] recatl that icons provide more concise and more rapidly assimilable information, especially for persons with difficulties to read. In order to minize semantic
distance [4] between the task to be accompli-
shed and the representation, icons must be close of user’s mental representation. Despite that statement, abstract icons are more recognizable by the users than their concrete counterparts which are less readable. This idea is similar in the domain of word processing [1].
:J=-J Figure
1.
l!!!!i
Asbtract and concrete icons.
For example, a simple bank-note icon is proved to be more readable than the complete image (fig. 1) Icons
must
convey
a clear
imagery,
without
ambiguity.
Ambiguity was identified between icons meaning a user’s choice confirmation, negation, going to next or previous
25
screen, undoing
some action and quitting
the application.
nu selection also requires no mental navigation the short-term
“~g~~
$~~ge8&#E&&h Use mouse buttons carefully Assigning two different actions to two buttons of the mouse promotes a high error rate because mental disabled persons
m=Figure
2. Ambiguous
Ambiguous
to reduce
memory load.
icons (fig.
icons 2) were rejected
for unambiguous
icons (fig. 3) found by progressive refinement.
do not differentiate
the mouse buttons. The same action
should be assigned to all the mouse’s buttons. operations
based on the number
impractical
because users cannot remember
Moreover,
of mouse cliking
are
actions asso-
ciated to one, two or more clicks on the buttons.
Colour selection shoud focus on user guidance. Searching word in a text is three times faster when the searched item is coloured wiLh a formerly-known, rarely
FUTURE WORKS These guidelines will be formally validated as experimental tests to be conducted with a screen evaluation tool. With these data, an evacuation work can be accomplished to set different parameters in interactive applications according
used and different colour than in the rest of the text [7]. Nevertheless, searching a word with a frequently used co-
to the type of population: with disabilities.
Figure
3. Unambiguous
icons
MCD persons, children,
persons
Iour is slower than with an unusual one. This conclusion suggests to usc few conventional
colours (e.g. red for dan-
ger or expense, green for safety or income). Users who are unable to read the text on the screen were guided by the colours of the symbol, if they are not colour-deficient viewing users.
REFERENCES Green, A.J.K. and Barnard, P.J., Iconic Interfacing : [1] the role of icon distinctiveness and jixed or variable screen locations, in Proceedings of the Third IFIP
TC13 Conference on Human-Computer Interaction INTERACT’90 (Cambridge, Augustus 27-31, 1990), Diaper, D., Gilmore, D., Cockton, G. and Shackel, B. (eds.), Elsevier Science Publishers, Amsterdam, 1990, pp. 457-462.
Display speed should be adequate Setting the parameters of scrolling and displaying speeds are vital because every changing interaction object on the screen will not be perceived if normat rate is used. Common progress-indicator are unusable for persons with disabilities
[2]
due to fast evolution [3]
Use speech synthesis to reinforce visual channels Vocal transcriptions of screen titles, labels, questions to the user were used not in order to substitute text on screens, but in order to reinforce screen textual information presented and for deficient-vision users. Use appropriate menu selection Menu selection and direct manipulation
already
[4]
A., Graphic
Design for
[5]
Pull-down menus causes three comprehension difficulties : they can hide paxt of information to the user (if one part of the list is invisible), selection mecanism is not evident
[7]
(confusion between point/clik, double-click, scroll/click) and articulator distance [4] becomes too important for Me-
[6]
Docu-
rial Series, New York, 1991 Noirhomme-Fraiture, M., Evaluation
of software for people with mental disabilities, Proceedings of World Congress on Technology (Washington, Dec. 1-5, 1991), Vol. 5, pp. 810-821. Norman, D. A., Cognitive Engineering, chapter 3 in User Centered Design - New Perspectives
have been selected
such a user (too much physical actions are performed).
Electronic
ACM Press Books Tuto-
Computer Interaction, Norman, S.W. (eds.), Lawrence Erlbaum
as interaction styles. No more than five items were efficiently used simultaneously for selection K (i) the selection is made on the label itselfi (ii) textual label is redundant with vocal transcription and graphical presentation; (iii) no pull-down menu are displayed.
26
Marcus,
ments and User Interfaces,
on Human-
D.A. and Draper, Associates Publi-
shers, NJ: Hillsdale, 1986, pp. 31-61. SaIapatek, P., Visual Scanning of Geometric Figures by the Human Newborn, Journal of Compar. Physiol. Psychol., 1968, pp. 247-258. Shneiderman, B., Designing the User interface: Strategies
for
Effective
Human-Computer
Interaction,
2nd cd., Addison-Wesley, Reading (Massachusetts), 1992. Van Nes, F.L., Juola, J.F. and Moonen, R.J.A.M., Attraction and Distraction by text Colours on Displays,
in Proceedings
of the Second HP
TC13
(Stuttgart, September 1-4, 1987), Bullinger, H.J. and Shackel, B. (eds.), Elsevier Science Publishers, Amsterdam, 1987, pp. 625-630. INTERACT’87
