White's Illusion

White's illusion is a brightness illusion involving a striped, black-and-white grating in which some of the black or white stripes are replaced by gray rectangles of identical color, luminance and opacity to one another; despite being physically identical, the gray rectangles that border white stripes appear noticeably darker than the gray rectangles that border black stripes, so that each rectangle's perceived brightness shifts toward the brightness of the stripes bordering it above and below, rather than the stripes immediately beside it to the left and right. This outcome runs opposite to what a simple theory of lateral inhibition would predict, since a gray rectangle surrounded mostly by white ought to look darker by contrast under that theory, meaning lateral inhibition alone cannot explain White's illusion. A related effect, the Munker-White illusion, or Munker illusion, produces a comparable outcome when the horizontal stripes are given different colors rather than only black and white, an effect that is instead explained by reference to the Bezold effect, in which a color's apparent shade shifts depending on the colors immediately surrounding it.