Abstract

We are investigating the extent to which the perceived speed, direction, and smoothness of a rotating pattern depend on the symmetry period of the pattern (i.e., the amount of rotation required to bring the pattern into self-congruence). Subjects viewed patterns with either twofold (180°, e.g., rectangle), threefold (120°, e.g., triangle), or fourfold (90°, e.g., square) symmetry under various rates of stroboscopic illumination; rating scales were the dependent measure. Results indicate that perceived speed, direction, and smoothness of rotation depend not only on the stroboscopic sampling rate but also on the symmetry of the rotated pattern. These results correspond to predictions based on symmetry group theory.

© 1987 Optical Society of America