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 nature and cost of programming and the subsequent reprogramming of a movement's relative time and overall duration. Initial programming followed a fixed-order specification; knowledge of the necessary relative time was required before 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 completely reprogram the entire response. Complete reprogramming occurred even when the performer had correctly prepared the higher order relative-time component and only had to modify the overall duration of the movement. The data indicate that organizing movement timing before movement initiation is accomplished in a fundamentally different manner depending on whether the movement is being initially compiled or modified.