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The McCollough Effect
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The McColloch Effect
What is it?
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 alternately looks at a red horizontal grating and a green vertical grating for a few minutes, a black-and-white horizontal grating will then look greenish and a black-and-white vertical grating will then look pinkish. The effect is remarkable because, under certain circumstances, it can last up to three months or more.
How can you produce it?
The effect is inducted by looking at a test image. It contains oppositely-oriented gratings of lines, horizontal and vertical. Next, you have to stare alternately at two induction images similar to the ones in the next slide.
One image should show one orientation of grating (here horizontal) with a colored background (here red) and the other should show the other orientation of grating (here vertical) with a different, preferably oppositely-colored background (here green). Each image should be gazed at for several seconds at a time, and the two images should be gazed at for a total of several minutes for the effect to become visible.
You should stare approximately at the center of each image, allowing the eyes to move around a little. After several minutes, you should look back to the test image; the gratings should appear tinted by the opposite color to that of the induction gratings (i.e., horizontal should appear greenish and vertical pinkish).
The Effect
The anti-McCollough effect
In 2008, a similar effect with different results was discovered, and has been termed the "anti-McCollough effect". This effect may be induced by alternating pairings of gratings in parallel alignment, one achromatic (black and white) and the other black and a single color (say black and red). If the color used was red, then after the induction phase the achromatic grating appeared slightly red. This effect is distinct from the classical effect in three important regards: the perceived color of the aftereffect is the same as the inducer's color, the perceived color of the aftereffect is weaker than the classical effect, and the aftereffect shows complete interocular transfer. Like the classic effect, the anti-McCollough effect (AME) is long lasting. Despite producing a less saturated illusory color, the induction of an AME may override a previously induced ME.
COMPETITIVE ANALYSIS
Properties
McCollough originally reported that these aftereffects may last for an hour or more. However, Jones and Holding (1975) found that 15 minutes of induction can lead to an effect lasting 3.5 months
The effect is different from colored afterimages, which appear superimposed on whatever is seen and which are quite brief. It depends on retinal orientation (tilting the head to the side by 45 degrees makes the colors in the above example disappear; tilting the head by 90 degrees makes the colors reappear such that the gravitationally vertical grating now looks green). Multiple effects can be stacked by inducting with multiple sets of grids.
Any aftereffect requires a period of induction with an induction stimulus (or, in the case of the McCollough effect, induction stimuli). It then requires a test stimulus on which the aftereffect can be seen. In the McCollough effect as described above, the induction stimuli are the red horizontal grating and the green vertical grating
Explanation:
https://www.youtube.com/watch?v=Wm8ZoVQ_OJo
Video version:
https://www.youtube.com/watch?v=nfwJxnijBno