Depth perception in moving line patterns.

By means of a computer system, the two-dimensional projections of a three-dimensional random wire figure, rotated clockwise (CW) or counterclockwise (CCW) about the vertical axis, were produced and displayed on a CRT. Generally the stimulus display appeared as an object rotating in depth, changing direction of movement frequently from clockwise rotation to counterclockwise, and vice versa. In the experiment, the three subjects observed the displays of three different types of projection, two polar projections and a parallel one. They were instructed to judge the direction of the seen motion and asked to report it using the button-switches. Both duration of the rotation perceived in either direction and frequency of the apparent reversals between those two were measured from the output sheets of a pen-recorder. The results showed the effects of the type of projection. (1) The veridical motions were perceived more continuously and durably in the polar projections than in the parallel one, (2) the opposite relation was found with the nonveridical motions, and (3) the reversals of moving direction were seen more frequently in the parallel projection than in the polar ones.