An experimental investigation of changes to visual size perception in conjunction with motor learning in a line tracing task

In this paper, we investigate whether motor learning affects visual size perception in humans. Our hypothesis is that motor learning tasks requiring precise manipulation or careful control of movement increase visual size perception. As a motor learning task, a line tracing manipulation involving fine position control of the hand was selected. By presenting horizontal or vertical bars at a variety of different widths, we were able to test for changes in visual size perception by examining subjects before and after the line tracing task. The results indicate that a horizontal bar looks thicker to the subjects after horizontal line tracing and a vertical bar looks thicker after vertical line tracing. Motor learning is thus accompanied by changes to visual perception.