Speed of apparent motion and the wagon-wheel effect
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.