Utilising Movement Planning to Improve Computer Accessibility for People with Cerebral Palsy: Potential, Benefits, and Costs

Abstract

Cerebral palsy (CP) is a common physical disability that results in activity limitation and reduced participation in society. Computer mouse accessibility is important for participation in work and educational settings. This thesis investigates making use of movement planning ability to improve mouse-based target acquisition for people with CP. Initial experiments studied CP’s effects on movement planning. For reaching tasks across different planning conditions, temporal coordination (eye-hand movement onset asynchrony) was generally similar between participants with and without CP. Notably, movement durations were significantly longer for the group with CP. This suggests that movement execution difficulties are making a greater contribution to activity limitation than any movement planning deficits. A mouse-based target acquisition method (the expansion cursor) was then devised that aimed to allow users to plan around difficult movements and improve small target acquisition. To make use of planning ability, users must have choice when planning an interaction. The expansion cursor is a zoom lens that users can choose to utilise or ignore at every individual click. The zoom can be utilised by holding down the mouse button for an extended period when clicking. The zoom function can also be ignored by clicking quickly as per typical computer use. In a user evaluation, using the zoom functionality improved accuracy for small targets. The expansion cursor effectively allowed users to replace one movement to a small target with two movements to larger targets, but this increased acquisition times. In the final experiment, the potential for two movements to larger targets to be more efficient than a single movement was evaluated. Results suggested that two movements are only faster when the smaller single target requires many corrective movements. In conclusion, using movement planning ability has great potential to improve accessibility of acquiring small targets without segregating users. However, introducing choice is unlikely to improve speed, and it is difficult for this choice to be readily available to the user without affecting typical use in some small way.