Abstract
Binocular rivalry is typically studied with a dichoptic stimulus whose half-images have similar figural contour (eg square frame) but different internal patterns (eg horizontal vs vertical lines). But given the importance of figural contours in defining the perceived binocular surface shape, one needs to examine how figural contours affect rivalry. To show that figural contours promote rivalry dominance, we used a large (10×10 deg) vertical grating surface as the binocular background. (i) Upon this a 1 deg circular horizontal grating patch (figural contour) was added to one half-image. When this display was viewed, little rivalry was observed. Instead, a relatively stable horizontal patch was perceived against the larger vertical grating. (ii) But if a thin lined circle, or a circular illusory contour, was added to the other half-image corresponding to the circular patch, a vigorous rivalry ensued. Curiously, when (i) was repeated with a binocular background consisting of either a checkerboard or random dot texture with rich microstructure or local edge information, vigorous rivalry was observed. Thus, our findings suggest that monocular, real or illusory, figural contours can tilt the dominant rivalry percept, in favor of the image that owns the figural border. In a second experiment, we showed that such border-ownership constraint also applies to the typical rivalry stimulus. Capitalizing on the rivalry dominance-spreading observation (Blake et al, 1992; Wilson et al, 2001), we tested observers with a red horizontal grating (LE) and a green vertical grating (RE). A border-ownership constraint predicts that the small occlusion-valid areas at the figural contours of each half-image (LE: red at the right margin; RE: green at the left margin), as centers for dominance-spreading, will be more immune to rivalry suppression. Confirming this, our observers reported more dominance for the occlusion-valid areas for stimulus duration of 100 msec and longer.
Supported by an IRIG grant from UofL and SCO Research Funds