A STUDY OF THE APPLICATION OF FITTS LAW TO SELECTED CEREBRAL-PALSIED ADULTS

Fitts' Law was applied to the evaluation of discrete aimed arm movemen ts in one dimension performed by 6 adults with cerebral palsy and 6 ad ults with normal movement. Targets (1.27, 3.81, 6.35, 8.89 cm in width ) placed at distances of 20.32, 30.48, 40.64, and 50.80 cm provided In dices of Difficulty of 2.19 to 6.32 bits. A video game was used for th e signal to move. The t tests for corrected means showed that the cere bral palsied group had greater reaction and movement times than the no rmal group. Linear regression analyses for pooled data and for the ind ividual cerebral palsied subjects showed (a) no relationship between r eaction time and Index of Difficulty for either group and (b) a negati ve, linear relationship between reaction time and Index of Difficulty for 1 cerebral palsied subject. Movement time was linearly and positiv ely related to the Index of Difficulty for the normal group but not fo r the cerebral palsied group. Two cerebral palsied subjects had moveme nt times which conformed to Fitts' Law. While the exceptions to Fitts' Law may be due to the limited range of movement and spasticity caused by severe cerebral palsy, there are indications that two of the cereb ral palsied subjects were performing ballistic rather than visually gu ided aimed movements. Fitts' Law may still apply when the distances an d target positions are individualized to conform to subjects' specific limitations and when the signal to move is auditory rather than visua l.