Abstract

Structure-from-motion studies typically employ motion sequences in which any single frame is devoid of any 3D structure information. Real world sequences, however, present the observer with both dynamic and static form cues. To investigate how these concurrently active sources of 3D information interact, we designed stimuli that, upon moving, provide inconsistent structure cues, i.e., the form cues suggest a 3D organization different from that indicated by motion cues. We showed (Sinha, 1992) that in such stimuli form cues can overwhelm the motion cues and that the rigidity assumption is extremely fragile in such situations (rigid objects are perceived as deforming non-rigidly). Here we bring further evidence to these hypotheses in a psychophysical study of motion perception in a patient, AMG, with an occipital-parietal lesion, whose form perception was normal. AMG could not extract 3D structure from motion cues alone, but when both static form and dynamic cues were available, her interpretation of moving stimuli (in terms of perceiving rigidity or non-rigidity) was similar to that of control subjects.

© 1992 Optical Society of America