Effects of age and disability on tracking tasks with a computer mouse: accuracy and linearity.

Many individuals with movement disorders are unable to make efficient use of graphical computer interfaces commonly employed in personal computers. In this study, performance limitations in target tracking with a computer mouse were studied for eight young subjects aged 19 to 29 (M = 23, SD = 3), four old subjects aged 70 to 73 (M = 72, SD = 1), and five motor-disabled subjects aged 37 to 74 (M = 65, SD = 16). Subjects tracked simple one- and two-dimensional motions at various frequencies. Performance was measured using an accuracy index derived from root-mean-square error, and a linearity index based on coherence estimation. A maximum bandwidth of 2 Hz for accuracy of mouse use was found, which often decreased due to advanced age or motor disability. Tracking linearity of all groups decreased as frequency increased. A significant degree of nonlinearity existed in all results (p < 0.05), with disabled subjects nearing complete nonlinearity in two-dimensional tracking. The data show that with advanced age and disability, mouse use becomes increasingly inaccurate and nonlinear. Assistive computer interfacing techniques, such as signal filtering, may improve mouse use.