Frequency of apparent reversal of rotary motion in depth as a function of shape and pattern

Abstract

Three experiments concerned with the effects of stimulus shape and surface pattern on frequency of apparent reversal of rotary motion (Ames effect) are reported. A standard 20 r.p.m. trial and a non‐verbal response were used throughout. The data from Experiments 1 and 2 show that whereas trapezium shapes have a high apparent reversal frequency irrespective of surface pattern (“window,” bars and plain) rectangular shapes seldom exhibit reversal. In Experiment 3 it is shown that similar reversals occur frequently with a circular elliptical and “nonsense” shape. It is concluded that a “window” pattern and perspective is not a critical determinant of apparent reversal and a general theory to explain the effect studied as well as reversals in static three‐dimensional figures is outlined.