“Munker-White Illusion”

From Michael’s “Visual Phenomena & Optical Illusions”

On the right you see many horizontal black stripes and two vertical blue bars. Do the blue bars have identical luminance? They certainly differ in perceived brightness. Grab the slider with the mouse and observe the startling change in brightness when the black grating is moved away from the blue bars.

Comment

Lateral inhibition predicts the opposite effect, so the mechanism must be quite different. See Corney & Lotto (2007) for a promising new explanation approach. White (1979, 1981) described these luminance effects, called White's illusion or Munker-White illusion. When the horizontal stripes differ in color (not black/white as here), strong color shifts result, the Munker illusion.

Sources

Anderson BL (1997) A theory of illusory lightness and transparency in monocular and binocular images: the role of contour junctions. Perception 26:419–453

Taya R, Ehrenstein WH & Cavonius CR (1995) Varying the strength of the Munker-White effect by stereoscopic viewing. Perception 24:685–694

White M (1979) A new effect on perceived lightness. Perception 8:413–416

White M (1981) The effect of the nature of the surround on the perceived lightness of gray bars within square-wave test gratings. Perception 10:215–230

White M (2010) The Early History of White’s Illusion. Colour: Design & Creativity 5:7,1–7 [PDF]

Demo from Ted Adelson’s site

Corney D, Lotto RB (2007) What Are Lightness Illusions and Why Do We See Them? PLoS Comput Biol 3:e180
This interesting paper shows that this illusion “automatically” occurs as a by-product when an artificial neural network is trained for brightness constancy.