The Influence of Binocular Disparity and Motion Parallax on Shape Constancy

Many studies on shape constancy have been made with 2D shapes presented at varying slants. When object is close, shape constancy is quite good (Lappin & Preble, 1975). Shape constancy declines as the degree of slant increases even with binocular presentation (Massaro, 1973). At large viewing distance, the degree of shape constancy depends on pictorial information (Gogel, 1978). These results suggest that shape constancy is influenced by whether accurate depth is provided. In the current study, the influence of binocular disparity and motion parallax on shape constancy is investigated at near distance. Test stimulus was a square presented at varying slants in a dark room. Subjects responded apparent slant and shape with stereo cue only, with motion cue only, or with the both cues. The apparent slant was veridical with stereo cue only, with motion cue only, and with the both cues. The decline of the shape constancy, however, differed according to cue. The binocular cue yielded shape constancy more than monocular cue.