Investigation of the parameters affecting Fitts' law on reciprocal arm movements

Abstract

The speed-accuracy trade-off in motor tasks is well-known. An error within a movement can increase with the speed of the movement. Fitts’ law formulizes the relationship between speed and accuracy. Several studies have confirmed the validity of Fitts’ law in various types of motor tasks. However, the reason why this law can provide a good regression of the movement duration on the speed and accuracy of the movement has not been clarified. In this study, the influence of the dynamic parameters of arms, the magnitude of the signal-dependent noise, and a criterion of movement smoothness on the Fitts’ law was investigated to gain insight into the speed–accuracy trade-off. Computer simulations of a reciprocal arm movement task were examined. Moreover, it was attempted to interpret the speed–accuracy trade-off by mathematically approximating a human arm as a mass–damper system. Consequently, it was revealed that positive viscosity did not affect the motor control based on the Fitts' law, whereas negative viscosity prevented obedience to the law.