CUES TO ILLUMINATION DO NOT CAUSE COREN AND KOMODAS ILLUSION OF LIGHTNESS IN AN AMBIGUOUS TUBE

The inside of a picture of a uniformly gray tube drawn with black circ les appears lighter than the outside. Coren and Komoda, who first desc ribed this illusion, argued that observers take illumination into acco unt to infer that the inside is lighter. That is, the inside of the tu be should receive less illumination than the outside but reflects the same amount of light into the eyes. Observers, therefore, infer that i t must be lighter. The inside of a gray tube drawn with white circles should appear lighter as well according to this account, but the exper iments reported here show that the outside appears lighter in such a t ube. We believe that depth perception is involved in this illusion but that lightness constancy is not.