Binocular Rivalry

Binocular rivalry is a visual phenomenon in which perception alternates between two different images, each presented separately to one eye, rather than the two images being merged into a single combined view. When sufficiently different images are shown to each eye at the same time, a method called dichoptic presentation, the brain does not fuse them; instead, one image dominates conscious perception for a period of several moments before the other image takes over, and this alternation continues, apparently at random, for as long as a viewer continues to look. During the switch between one dominant image and the other, viewers can experience brief, unstable composite perceptions, such as a set of vertical lines seeming to gradually replace a set of horizontal lines in a pattern resembling a slowly traveling wave rather than an instantaneous switch. The phenomenon occurs whenever the two images differ enough, whether through simple stimuli such as differently oriented lines or complex stimuli such as a face shown to one eye and a house to the other, while sufficiently similar images instead produce ordinary single vision and stereoscopic depth perception. Binocular rivalry has been extensively studied using neuroimaging and single-cell recording techniques as a tool for investigating the neural basis of which of two competing visual inputs becomes dominant in conscious perception.