Binocular rivalry Guide, Meaning , Facts, Information and Description
Binocular rivalry is a phenomenon of visual perception. It occurs when an image is presented to one eye and a very different image is presented to the other. Instead of the two images being seen superimposed, one image is seen for a few moments, then the other, then the first, and so on for as long as one cares to look. For example if a set of vertical lines is presented to one eye, and a set of horizontal lines to the same region of the retina of the other, we see alternations between the vertical and horizontal lines. At transitions, brief, unstable composites of the two images may be seen; these are often organized. For example, the vertical lines may appear to obscure the horizontal lines from the left or from the right, or the horizontal lines make appear to obscure the vertical lines from the top or from the bottom. When the images presented to the eyes have different contours, rivalry is referred to as ``binocular contour rivalry. When the images presented to the eyes have different colours, rivalry is referred to as ``binocular colour rivalry.Binocular rivalry is interesting because visual consciousness changes without any change in the images presented to the eyes. If the part of the nervous system could be found at which neural activity goes from reflecting the unchanging images to reflecting the changing perception, then a neural correlate of consciousness (and the site of the mechanism of binocular rivalry) would have been found.
Binocular rivalry was discovered by Porta (1593, as cited in Wade, 1996). Porta put one book in front of one eye, and another in front of the other. He reported that he could read one one book at a time and that changing from one to the other required withdrawing the ``visual virtue'' from one eye and moving it to the other. According to Wade (1998), binocular colour rivalry was first reported by Le Clerk (1712). Desaguiliers (1716) also recorded it when looking at different colours from spectra in the bevel of a mirror. The clearest early description of both colour and contour rivalry was made by DuTour (1760, 1763; see translations by O'Shea, 1999a,b). To experience colour rivalry DuTour either crossed his eyes or overdiverged his eyes (a form of free fusion commonly used also at the end of the 20th century to view Magic Eye stereograms) to look at differently coloured pieces of cloth (DuTour, 1760) or differently coloured pieces of glass (DuTour, 1763). To experience contour rivalry DuTour again used free fusion of different objects or used a prism or a mirror in front of one eye to project different images into it. The first clear description of rivalry in English was by Wheatstone (e.g., 1838). Wheatstone invented the stereoscope, an optical device (in Wheatstone's case using mirrors) to present different images to the two eyes.
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