Planning and executing simple movements: Contributions of relative-time and overall-duration specification

In 3 experiments, the authors used a precuing protocol to examine the natur e and cost of programming and the subsequent reprogramming of a movement's relative time and overall duration. Initial programming followed a fixed-or der specification; knowledge of the necessary relative time was required be fore information regarding overall duration could be used in a manner that expedited response planning. In the case of reprogramming, however, when a modification had to be made in either the relative time or overall duration of the anticipated and already-prepared response, performers chose to comp letely reprogram the entire response. Complete reprogramming occurred even when the performer had correctly prepared the higher order relative-time co mponent and only had to modify the overall duration of the movement. The da ta indicate that organizing movement timing before movement initiation is a ccomplished in a fundamentally different manner depending on whether the mo vement is being initially compiled or modified.