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Vision Research 39 (1999) 12731284 Stereoscopic occlusion and the aperture problem for motion: a

Summary: Vision Research 39 (1999) 1273­1284
Stereoscopic occlusion and the aperture problem for motion: a
new solution 1
Barton L. Anderson
Department of Brain and Cogniti6e Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Received 22 April 1998; received in revised form 3 August 1998
Recent work has shown that the ability of moving contour terminators to determine the perceived motion of untextured
contours is strongly constrained by whether contour terminators are classified as intrinsic (belonging to a moving contour) or
extrinsic (belonging to a surface occluding a moving contour). It has also been demonstrated that stereopsis can play a decisive
role in this classification. Specifically, Shimojo, Silverman and Nakayama (1989, Vision Research 29, 619­626) argued that the
efficacy of stereopsis in classifying moving contour terminators as intrinsic or extrinsic stemmed from the relative depth
relationships specified by binocular disparity. Here, evidence is presented which demonstrates that the visual system relies on the
presence of unpaired contour terminators to classify stereoscopic contour terminators as extrinsic. The author shows that the
tendency to perceive untextured contours translating in a single rectangular aperture in a direction parallel to the longer axis of
the aperture (the barberpole illusion) was not abolished by stereoscopic depth differences when the contour terminators were
interocularly paired. However, the illusion was abolished when the contours terminators along the longer axis of the aperture were
interocularly unpaired. Moreover, contours translated within a square aperture revealed a systematic shift towards the direction
of motion signaled by the binocularly paired contour terminators along the horizontal edges of the aperture. These results
demonstrate that the classification of stereoscopic contour terminators along an extrinsic­intrinsic dimension results from the


Source: Anderson, Barton L. - School of Psychology, University of Sydney


Collections: Biology and Medicine