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.
GregoryR. L.WallaceJ. G.CampbellF. W.Changes in the size and shape of visual after-images observed in complete darkness during changes of position in space. Quart. J. exp. Psychol., 1959, 11, 55–56.