What is the McCollough Effect?

The McCollough effect is a fascinating brain reaction 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. Was originally described by Celeste McCollough in a paper in Science in 1965.

It’s something that can’t be unseen… sometimes affecting your vision for months! This effect can be understood without subjecting yourself to it. So, better to not try it ;)

The effect laid out in her paper involves patterns of horizontal and vertical bars. First a subject stares at black and white patterns. Then alternating patterns of horizontal red and black bars and a set of vertical green and black bars (called adaptation). This causes a bit in your brain to be set. The result of this is the ability to detect these patterns and indicate the detection of one of the adapted patterns by seeing its complimentary color. Where there is only black and white the brain now sees black and light green, or black and pink.

This image shows the sets of horizontal and vertical bars, the center column labeled “adapt” contains the two variations of the bars with complimentary colors (red and green) which is how you would set the bit as I described above. Once this process has gone on for a few minutes (2 to 4 minutes seems to be the average time required) you can then look at the set of images on the left for the magic to happen. The resulting effect is simulated by the color overlay in the far right column labeled “post-adapt”.

There is quite a bit of evidence that suggests the McCollough Effect (ME) takes place in the brain and is not merely a result of fatigued rods and cones in the retina. There has been quite a bit of work to determine where the ME takes place in the brain, some of which can be found on the ME scholarpedia page of which Dr. McCollough is the curator.

The McCollough Effect is thought to involve the monocular pathways at an early stage of the visual cortex. This is based on multiple theories which include evidence provided by other published works. One of the more interesting of these is that the ME can be generated with images that alternate at frequencies up to 50Hz, which is too fast to consciously perceive the color and orientation relationships. The ability to generate the ME at this frequency are consistent with properties of the early cortical areas, which include the primary visual cortex (V1).

The ME has lasted 3.5 months in extreme cases, however a modest exposure to the ME adaptation images of only a few minutes can have a lasting ME of 24 hours or more.

The McCollough Effect has interesting properties that are still not well understood. As a chromesthet I've tried this multiple times but has no effect on me.

References:http://www.scholarpedia.org/article/McCollough_effect
http://hackaday.com/2016/01/06/hack-your-brain-the-mccollough-effect/

If you want to experience the McCollough Effect -
not recommended :http://lite.bu.edu/vision-flash10/applets/Color/McCollough/McColloughNoSound.html

Journal article:http://science.sciencemag.org/content/149/3688/1115