Intermanual interactions during programming of aimed movements: Converging evidence on common and specific parameters of control

Summary Reaction time for choice between left-hand and right-hand responses sometimes depends on whether the responses assigned to the two hands are the same or different, but sometimes it does not. It has been suggested that the result obtained indicates whether the variable on which the responses differ is determined by common or specific parameters of control. Common parameters apply to movements of both hands, but specific parameters can be set independently for left-hand and right-hand responses. The interpretation of choice RT in terms of intermanual interactions requires that the conclusions converge with conclusions that are based on studies of simultaneous movements, provided that interactions can indeed be attributed to common parameters. Results from the latter type of experiment suggest that duration of aimed movements is determined by common parameters, but amplitude is determined by specific parameters. In two experiments it is shown that the choice-task results are consistent with this conclusion: Choice RT increases when the choice is between aimed movements that differ in duration, but not if the choice is between movements of different amplitudes. Further, an assimilation of responses is found in the former case but not in the latter. These findings are taken as further support for the notion of intermanual interactions during motor programming.