S. Keates, P. J. Clarkson and P. Robinson University of Cambridge, Department of Engineering (CUED), Trumpington Street, Cambridge, CB2 1PZ, United Kingdom.
Conventional computer interfaces and input systems present serious difficulties to users with impaired motion. Conditions exhibiting such impairments include Cerebral Palsy, Muscular Dystrophy, spinal injuries, Parkinson's Disease, strokes and severe arthritis. Frequent symptoms include tremor, spasm, poor coordination and restricted movement. There are two approaches to designing an interface for a wider range of user capabilities. The first, adaptation, involves design for a particular application and then tailoring retrospectively for different users. The second, proactivity, involves broadening the definition of user capability at the outset of the design process ( Stephanidis 1995, Stary 1997).
There is growing support for the proactive approach. It has been claimed that fundamental changes to the design philosophy are required to make interfaces more accessible and usable ( Karshmer 1997). Recent discussions about user interfaces for all have shown that traditional HCI approaches are not the best way to achieve universal accessibility and that more specific studies are required to reach this goal ( Stephanidis 1997). However, implementing a proactive approach requires a different emphasis from typical interface development practice, where conformity of style may have greater emphasis than function. For example, it is known that for assistive devices, traditional design techniques are yielding products that are neither usable nor commercially successful ( Buhler 1998).
Implementing a proactive approach requires providing the designer with guidance on how to design for a wider range of capabilities. A typical solution is to produce guideline information about issues that should be considered.
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