The McCollough Effect is a phenomenon in which a person's perception of color is altered after prolonged exposure to black and white images. It was first discovered by American psychologist Celeste McCollough in 1965 and has been studied extensively since then. The effect is thought to be caused by
The McCollough effect is a phenomenon of human visual perception in which colorless gratings appear colored contingent on the orientation of the gratings. It is an aftereffect requiring a period of induction to produce it. For example, if someone alternates between looking at a red horizontal grating and a green vertical grating for a few minutes, a black-and-white horizontal grating will appear greenish, and a black-and-white vertical grating will appear pinkish. The effect is remarkable because, although it diminishes rapidly with repeated testing, it has been reported to last up to 2.8 months when exposure to testing is limited.