McCollough Effect

The McCollough effect is a phenomenon of visual perception where an individual perceives a grating (grid of black and white bars) as having color, after prolonged viewing of a colored grating.

The effect is an example of neural adaptation, where the brain adjusts to the stimuli it receives.

Look at each side of the following image for 30 seconds, then turn your gaze to the white grids below. The white horizontal stripes should appear greenish, and the white vertical stripes should look reddish.


McCollough effect
McCollough Effect


McCollough effect
McCollough Effect


Table of Contents


How does the McCollough Effect work?

The McCollough effect works by a process called neural adaptation, which refers to the change in the responsiveness of neurons in the visual cortex to a stimulus over time.

The process occurs when the individual looks at a colored grating pattern, which causes the neurons in the visual cortex to become adapted to the particular hue of the grating.

When the individual then views a grating with a different orientation, the brain continues to perceive the afterimage of the original grating with its hue, leading to a cross-orientation interaction where the grating appears to have a color.

The effect can persist for several minutes to hours, even after the individual stops viewing the grating.

Versions of the McCollough Effect

The following are other examples of the McCollough Effect



McCollough effect




McCollough effect



Illusions like McCollough Effect

The McCollough effect is a type of afterimage illusion.

An afterimage is an optical illusion that occurs when a person looks at a bright image for a short period and then looks away, causing a complementary image to persist for a short time.

The McCollough effect is a specific type of afterimage illusion that involves the perception of color in an image that is actually grayscale.

It results from a change in the responsiveness of neurons in the visual cortex to a stimulus over time, which is known as neural adaptation.

Some related illusions include the following:

Persistence of vision is the phenomenon by which the brain continues to perceive an image even after the image is no longer present.

This occurs because the cells in the retina, called rods and cones, take a brief period of time to “reset” after being stimulated.



A color constancy illusion is a type of visual illusion in which a color appears to be different when viewed in different contexts.

For example, the same patch of color may appear lighter or darker when viewed against different backgrounds, or may appear to change color when viewed under different lighting conditions.


Color constancy
Color Constancy


The afterimage illusion is a type of visual illusion in which an image continues to appear in the observer’s visual field after the original stimulus has been removed.

This can occur due to the persistence of neural activity in the visual system, and can take the form of a positive afterimage (an image that is the same color as the original stimulus) or a negative afterimage (an image that is the opposite color of the original stimulus).


The Checker Shadow Illusion is created by a checkerboard pattern composed of squares with different luminance values, the squares that are not directly illuminated by the light source appear darker than the illuminated squares, creating the illusion of shadows.


Edelson-Checker_shadow_illusion
Checker Shadow Illusion


The simultaneous contrast illusion is a visual effect that occurs when the perception of a color is affected by the colors of the surrounding area.

The illusion creates the appearance of a change in the color of an object, even though the actual color of the object remains constant.


Simultaneous Contrast Effect
The center green dot is the same on both sides, but the surrounding color changes the perception


The Neon Color Spreading illusion refers to the visual phenomenon where an area of color appears to spread or “bleed” beyond its intended boundaries.

Neon Color Spreading
From Wikimedia Commons


The Bezold Effect: This illusion is created by placing two or more colors next to each other, and the way they appear to change when they are close to one another.  

Bezold_Effect
from Wikimedia Commons


The Cornsweet illusion is a classic example of a brightness illusion, which is an illusion in which two areas that are physically the same brightness appear to be different in brightness.

Cornsweet illusion
Cornsweet illusion


The Chubb illusion is based on the perception of brightness and can be observed when a small bright patch is surrounded by a larger dark area, the small bright patch will appear brighter than the same patch surrounded by a bright area.

Chubb Illusion

White’s illusion is a visual phenomenon in which two identical gray bars are placed on a background of alternating black and white stripes.

The gray bars appear to be different shades of gray, with the one on the white stripes appearing lighter than the one on the black stripes.

In the image below, both gray bars have the exact same color.


White's Illusion
White’s Illusion

The Watercolor Illusion: This illusion is created by the way the brain perceives edges of an object. When an object is surrounded by a colored halo, the object appears to have a different color than it actually does.

Watercolor Illusion



The Café Wall Illusion is a visual illusion that is created by a grid of alternating light and dark horizontal and vertical lines. The lines appear to be bent or tilted, even though they are actually straight.

Cafe Wall Illusion


Discovery of the McCollough Effect

The McCollough effect was discovered by American psychologist Celeste McCollough in 1965.

Celeste McCollough was an American psychologist and researcher who is best known for discovering the McCollough effect.

She conducted extensive research in the field of perception and color vision and made significant contributions to our understanding of how the visual system processes and represents visual information.

McCollough’s discovery of the McCollough effect helped to further our understanding of the underlying mechanisms of visual perception and how the brain processes and represents visual information.

References and Resources

Check out our complete list of illusions.

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