The utilization of visual feedback in the control of movement direction: evidence from a video aiming task.

The purpose of the present study was to establish the contribution of visual feedback in the correction of errors during movement execution (i.e., online) and the utilization of visual feedback from a completed movement in the programming of upcoming trials (i.e., offline). Participants performed 2 dimensional sweeping movements on a digitizing tablet through 1 of 3 targets, which were represented on a video monitor. The movements were performed with and without visual feedback under 4 criterion movement times (150, 250, 350, 450 msec). We analyzed the variability in directional error at 25%, 50%, 75%, and 100% of the distance between the home position and the target. There were significant differences in variability between visual conditions at each movement time. However, in the 150-msec condition, the form of the variability profiles did not differ between visual conditions, suggesting that the contribution of visual feedback was due to offline processes. In the 250-, 350-, and 450-msec conditions, there was evidence for both online and offline control, as the form of the variability profiles differed between the vision and no vision conditions.