Time course of movement planning: selection of handgrips for object manipulation.

A goal of research on the cognitive control of movement is to determine how movements are chosen when many movements are possible. We addressed this issue by studying how subjects reached for a bar to be moved as quickly as possible from a home location to a target location. Ss generally grabbed the bar in a way that afforded a comfortable posture at the target location (the end-state comfort effect) and with the thumb toward the end of the bar that would be aligned with the target (the thumb-toward bias). The data suggested that subjects chose handgrips by retrieving instances of previous reaches, not by carrying out computations that treated candidate reaches as new behavioral events.