title: 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 movements may also take into account the rewards or costs of any outcomes that may 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 for missing the targets. Subjects were asked to touch targets on an iPad® screen with different costs for missed targets. We manipulated the probability of error by comparing children with dystonia (who are characterized by increased intrinsic motor 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 in movement 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 how movement time in a Fitts-like task is related to perceived risk.
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bertucco
authors.affiliation: Department of Biomedical Engineering, University of Southern California, Los Angeles, California, United States of America.
authors.forename: Nasir H
authors.initials: NH
authors.lastname: Bhanpuri
authors.affiliation: Departments of Biomedical Engineering, Child Neurology, and Biokinesiology, University of Southern California and Children's Hospital of Los Angeles, Los Angeles, California, United States of America.
authors.forename: Terence D
authors.initials: TD
authors.lastname: Sanger
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D004192:Discrimination, Psychological; D004421:Dystonia / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D009048:Motor Skills; D009068:Movement