McCollough Effect
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.
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Origin
Discovered in 1965 by American psychologist Celeste McCollough (1926–2023) while teaching at Oberlin College. By showing students alternating orange-and-black vertical and blue-and-black horizontal gratings, she produced colored aftereffects that could persist for hours or even months — the first known contingent aftereffect in visual perception.
Updated February 22, 2026