7.3. Binocular Rivalry

In much of our visual field we see objects with both eyes (Figure 7.11). We have seen the the brain can usually fuse two images when they are very similar and and the angle of disparity is not too great. However, if we show one eye a very different image to the other eye, the brain cannot create a single perception. Instead, our perception quickly switches back and forth between the two images. For example, if the left eye views horizontal lines and the right eye views vertical lines, an observer will report seeing one of the images for a few seconds, then the other, then the first again, and so on for as long as he or she cares to look (Wheatstone, 1838).

Binocular rivalry is a popular tool for studying perception and awareness, because perception changes even when the physical stimulus does not. For this reason, rivalry is championed as a useful tool for studying the neural correlates of visual consciousness (Crick & Koch, 1990).