Programming of direction and velocity of an aiming movement: The effect of probability and response-specificity

Abstract

Two experiments are reported on the mutual relations between the effects on choice reaction time of relative frequency, average velocity of aiming movements, and of Response-specificity with respect to movement direction. The first study was a 2-choice task in which relative frequency (0.5; 0.2 vs 0.8) and average velocity (17.5 vs 70 cm/sec) were varied. Their effects were found to interact. In the second study a 4-choice task was employed in which movement direction (left vs right) and average velocity (17.5 vs 70 cm/sec) defined the response alternatives of which the relative frequency (0.5; 0.2 vs 0.8) was varied. Their effects were examined under high and low Response-specificity. Again a significant interaction between the effects of average velocity and relative frequency was observed, the size of which also depended on movement direction. Response-specificity had a small significant effect that was additive to that of the other variables. It is argued that Response-specificity affects the preactivation of the motor system, while average velocity, movement direction and relative frequency all affect Motor-programming.