Automaticity of online control processes in manual aiming.

Experiments that manipulated the visual feedback of the moving limb have suggested the existence of efficient and automatic online correction processes. We wanted to determine whether the latency/gain of the correction for a cursor jump are only influenced by the size of the cursor jump or whether they are also influenced by the need of a correction for the target to be reached. In Experiment 1, we used two target sizes (5 and 30 mm) and three cursor-jump amplitudes (5, 15, and 25 mm), so that for some target size/cursor-jump combinations, no correction would be needed to reach the target. Participants were not aware of the cursor jump, but we observed a 65% correction regardless of target size. In Experiment 2, participants pointed at a large target for which a 15-mm cursor jump never impeded target attainment. Participants modified the trajectory of their movement in the direction opposite to the cursor jump (42% of the cursor jump). Our results indicate that the latency of the correction for a cursor jump was not influenced by the size of the cursor jump or that of the target. However, the correction tailored the movement's initial impulse according to the target's characteristics.