Abstract
When searching for a target with eye movements, saccades are planned and initiated while the visual information is still being processed, so that subjects often make saccades away from the target and then have to make an additional return saccade. We previously showed that increasing the cost of passing the target, by having subjects move a window through which they could see the visual scene with their hand did not prevent such overshooting. In that case the eyes and hand follow the same path. Here we compare that condition with one in which a scene is moved behind a stationary window. The task was to find an O amongst Cs. We ensured that the required movement of the hand was identical in both conditions, so that any difference could be attributed to the relationship between movements of the eye and of the hand. Subjects found the target faster when moving the window than when moving the scene behind the window at the expense of making more overshoots. The relationship between overshoot and movement speed when comparing the two conditions was the same as the relationship between these two when comparing targets of different contrasts or different window size. We conclude that the hand overshooting the target is not directly related to the eyes doing so, but rather that moving on before the information has been fully processed is a general principle of visuomotor control.