Binocular Rivalry in Half-Occluded Regions of Coloured Random-Dot Stereograms

In normal perception, binocular rivalry does not arise in half-occluded regions. However, when coloured random-dot stereograms (RDSs) were observed, binocular rivalry arose in half-occluded regions. In this study, binocular rivalry in half-occluded regions was studied with coloured RDSs. Coloured RDSs consisted of a central square-shaped region, a background, half-occluded regions, and a probe. The central square-shaped region was coloured white, and was presented in either crossed or uncrossed disparity. The background was coloured yellow. The half-occluded regions were coloured either white, yellow, or blue. The probe was coloured red, and was presented in either of the half-occluded regions. Subjects judged the disappearance of the probe and stereopsis. When the half-occluded regions were coloured the same as the front plane, the probe and stereopsis both disappeared. On the other hand, when the half-occluded regions were coloured the same as the back plane or differently from both planes only the probe disappeared while stereopsis did not disappear. Also, disappearance of the probe decreased more when the half-occluded regions were coloured the same as the back plane, than when the half-occluded regions were coloured differently from both planes. These results suggest that half-occluded regions escape binocular rivalry for several reasons, including ecological validity in 3-D representation, and that half-occluded regions are suppressed interocularly when a static stereogram is observed statically.