The planning of precision movements.

Two experiments are reported in which subjects were required to make rapid aiming movements to targets of various sizes. Probe reaction time (RT) procedures were used to investigate the preparation of the response to the target. It was proposed that if the precision of movement was planned in advance, this would be reflected by the lengthening of RTs to probes presented during the latency phase of the response. The more precise the movement (to smaller targets) the longer will be the delays to the probes. The results generally supported the prediction and the probe RTs were correlated with target size. There was also some evidence that the probe was lengthening during the movement and in the region of the target.