Binocular Rivalry

CORE DEFINITION

Binocular rivalry is a visual phenomenon in which images entering the left and right eyes alternate in our perception. When two highly different images are presented to the two eyes at the same time, we find that what we perceive is not a composite of the two images, but rather one eye's image appears, then the other's, alternating continuously. For example, if a vertical stripe image is presented to the left eye and a horizontal stripe image to the right eye, the observer will see either all horizontal stripes or all vertical stripes. During the transition period of alternation, it is possible to see a brief and unstable composite of the two images. For instance, over a certain period, horizontal stripes may occlude vertical stripes from the left (or right), and vertical stripes may occlude horizontal stripes from the top (or bottom). Binocular rivalry occurs when the difference between the left and right eye images is sufficiently large, ranging from simple cases (such as images composed of lines in different orientations) to complex cases (such as different letters or different pictures, like a face and a house). However, when the difference between the left and right eye images is small, single vision or stereopsis results.