Perceived cost and intrinsic motor variability modulate the speed-accuracy trade-off

Abstract

Fitts' Law describes the speed-accuracy trade-off of human movements, and it is an elegant strategy that compensates for random and uncontrollable noise in the motor system. The control strategy during targeted movementsmay also take into account the rewards or costs of any outcomes thatmay occur. The aim of this study was to test the hypothesis that movement time in Fitts' Law emerges not only from the accuracy constraints of the task, but also depends on the perceived cost of error formissing the targets. Subjects were asked to touch targets on an iPad1 screen with different costs for missed targets. We manipulated the probability of error by comparing children with dystonia (who are characterized by increased intrinsicmotor variability) to typically developing children. The results show a strong effect of the cost of error on the Fitts' Law relationship characterized by an increase inmovement time as cost increased. In addition, we observed a greater sensitivity to increased cost for children with dystonia, and this behavior appears to minimize the average cost. The findings support a proposed mathematical model that explains howmovement time in a Fitts-like task is related to perceived risk. Copyright: