Binocular rivalry is a visual illusion that occurs when the two eyes are presented with incompatible images. Instead of perceiving a mixture of the two images, most people experience alternations in which only one image is visible at a time. Binocular rivalry works best under controlled laboratory conditions with prisms or mirrors, but if you are lucky you might be able to experience it in the figure below. Try crossing your eyes to align the left boxes and right boxes, so that three boxes ar...
