Illusory staircase Gelb effect

since March 15, 2006

"Illusory staircase Gelb effect"

The rightmost square appears to be white though they are identical.

Copyright Akiyoshi .Kitaoka 2006 (March 15)

Movie version

The Gelb effect refers to a phenomenon that in a homogeneously dark room an intensely lit black card appears to be gray or white. The card suddenly appears to be black when another white card is placed in the visual field (= lightness constancy).

The staircase Gelb effect is the striking demonstration of the Gelb effect exhibited by Professor Alan Gilchrist, Rutgers University. He used five cards of different luminances in the invited lecture held in Tokyo (March 14, 2006).  Related lecture 

Cataliotti J and Gilchrist A (1995) Local and global processes in surface lightness perception. Perception and Psychophysics, 57, 125-135.

Gilchrist A, Kossyfidis C, Bonato F, Agostini T, Cataliotti J, Li X, Spehar B, Annan V, Economou E.. (1999) An anchoring theory of lightness perception. Psychological Review, 106, 795-834.

Illusory staircase reverse Gelb effect

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