A Motor-Behaviour Model for Physically Challenged Users

A motor behaviour model simulates movement limits and capabilities of users for different input devices and interaction techniques (MacKenzie, 2003). For ablebodied users, most of the motor-behaviour models are based on Fitts’ Law (Fitts, 1954) and its variations (MacKenzie, 2003). For disabled users, there is growing evidence that their interaction patterns are significantly different from those of their able-bodied counterparts (Keates and Trewin, 2005) (Trewin and Pain, 1999). The applicability of Fitts’ law for motor-impaired users is a debatable issue. In general real life pointing tasks demand very fine coordination between vision and motor-action and in those situations motor-impaired persons do not precisely follow Fitts’ Law. There is a few work to develop an alternative of Fitts’ law for motor-impaired people. Gump et. al. (2002) found significant correlation between the movement time and the root of movement amplitude. Gajos, Wobbrock and Weld, (2007) estimated the movement time by selecting a set of features from a pool of seven functions of movement amplitude and target width, and then using the selected features in a linear regression model. We did a more detailed analysis of different phases of movement for several pointing tasks undertaken by motorimpaired users and develoed a statistical model to predict the movement time for a pointing task. Our predicted movement times have significantly correlated with the actual (p<0.002).