First Advisor

Gerald M. Murch

Term of Graduation

Summer 1975

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Psychology






Color vision, Visual perception, Conditioned response



Physical Description

1 online resource (iv, 40 pages)


A model based on the laws of classical conditioning is posed as an explanation for the McCollough Effect, an orientation-specific color aftereffect. This model stands as an alternative to the color-coded edge detector hypothesis. Background and relevant issues are presented. Two experiments were performed. The first demonstrated that an auditory stimulus causes the effect to appear stronger to some subjects, a disinhibiting effect. It was also shown that some subjects experience spontaneous recovery of the effect after it has been extinguished.

The second experiment demonstrated that the after-colors will generalize to lines of varying orientation, including 45°. Subjects adapted to both red-vertical and green-horizontal lines saw mostly pink on test lines more than 30° off horizontal. Subjects adapted to red only or green only saw the appropriate after-colors on patterns of all orientations between 0° and 90°. These results conflict with the color-coded, edge detector theory and an explanation in terms of classical conditioning is offered.


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