, Volume 41, Issue 1, pp 29-34

Speed of apparent motion and the wagon-wheel effect

Abstract

The speed of apparent movement of a stroboscopically illuminated spoked wheel was measured by counting the number of spokes passing a particular position per unit of time. This measure gave very stable values of speed, which compared closely to predicted speeds calculated from stimulus onset asynchrony and angular displacement values. The results provide, for the first time, a reliable measure of speed of one form of apparent motion. The traditional explanation for the wagon-wheel effect in terms of beta motion is discussed in light of several differences between the classical demonstrations of apparent motion and stroboscopic motion as seen on the wagon wheel.

This research was undertaken while the first author was on sabbatical leave at Queen’s University. The work was supported by Grant A0044 from the Natural Sciences and Engineering Research Council of Canada to P C. Dodwell and D. W. Murr D. J. Finlay was supported by a special grant from Queen’s University, and P. C. Dodwell by a Killam Research Fellowship.