The role of vision in repetitive circle drawing.

In the present experiment the role of vision in the control of repetitive circular movements was examined. Subjects drew circles at a 600 ms per circle rate. During the first nine seconds of the trial subjects moved with full vision and were paced by a metronome. During the latter 15 seconds, vision could be removed and/or the pacing signal could be removed. There were no effects of the pacing signal on the temporal and spatial characteristics of the circle. Withdrawal of vision did not affect the shape of the circle, but did change its scaler quality. The circles became smaller and the center drifted in a systematic fashion. Furthermore, the loss of vision produced an increase in variability in the circle shape, size and location. It is clear that in a simple task such as circle drawing, vision serves not as a source of information about form, but to maintain a stable and consistent form.