Developing a methodology for the design of accessible interfaces

Users with a number of different motion impairment conditions cannot cope with most current computer access systems. Such conditions include athetoid, ataxic and spastic Cerebral Palsy, Muscular Dystrophy, Friedrich’s Ataxia, tetraplegia and spinal injuries or disorder. Frequent symptoms include tremor, spasm, poor co-ordination, restricted movement, and reduced muscle strength. Similar symptoms are also seen amongst the elderly able-bodied population from conditions such as Parkinson’s Disease, strokes and arthritis. The primary aim of the programme of research at the University of Cambridge is to enable the design of accessible input systems and interfaces for all motion-impaired users, both elderly and disabled. Current interface design practices are based on user models and descriptions derived exclusively from studies of able-bodied users. However, such users are only one point on a wide and varied scale of physical capabilities. This paper will show that there are very important differences between those with motion-impairments, whether elderly or disabled, and able-bodied users when they interact with computers. Without a proper understanding of those differences, interface design will remain an exercise in making the interfaces more comfortable for the motion-impaired users, rather than really usable. This paper describes our experiments to understand how motion-impaired users interact with computers and how we are using this information to develop a methodology for the design of accessible interfaces.