Visual Constancy during Movement: 1. Effects of S's Forward and Backward Movement on Size Constancy

A novel method for estimating constancy is described, which is applied to the estimation of size constancy during motion of observers moved passively on a swing in darkness. Ss viewed a circle traced on an oscilloscope tube and arranged to shrink as S approached it and to expand as he moved away. The variation in size of the display was adjusted by E until it appeared of constant size to S during his movement. Constancy was greater during forward than backward movement.