Skip to main content
McCollough image

The Illusion That Can Break Your Brain

McCollough test imageWarning: Lenstore strongly advises against trying this illusion and accepts no liability if you choose to independently search for and view it. The illusion itself is not included within this article.

"Do not look at this illusion for more than a few seconds, or you’ll break your brain for months." This is the warning message that often accompanies any mention of the McCollough effect.

The McCollough effect is able to rewire your brain so that colour perception is altered beyond just temporary visualisations. It sounds incredible, but this ‘visual virus’ can cause you to see colours where none exist for over three months.

How Is The McCollough Effect Induced?

The McCollough effect involves two coloured gratings. One is red with horizontal black stripes, while the other is green with vertical black stripes.

To produce this effect, participants must first look at the black and white test image featured on the right. This image alone isn’t associated with any long-term effects on vision, so don’t be scared to have a look.

After confirming that the test image is colourless, participants then alternately stare at the two coloured gratings. Staring for just 10 seconds gives an effect that can last an hour or more. Looking at the illusion for 10 minutes or more has reportedly led to effects that can last for over three months.

What Does The McCollough Effect Make You See?

McCollough test image colourOnce the image has been stared at for enough time, participants will notice a change in the colourless test image. A green haze appears around the horizontal lines, while a magenta haze appears around the vertical lines. 

The long-lasting effects can prove troublesome when reading, or when working on colour-sensitive projects. 

The colours can vary in intensity between individuals, and extreme examples have even caused participants to see black lines as completely coloured. Coffee and psychoactive drugs have also shown to impact the duration and intensity of the effects.

How Does The McCollough Effect Work?

Most colour-altering illusions leave short-lived afterimages. These afterimages superimpose a certain colour over images within your field of view, before disappearing after a minute or so.

The McCollough effect differs from most illusions, beyond just the long duration. Afterimage effects from typical illusions will leave a shape of colour that follows the orientation of your vision. In contrast, individuals experiencing the McCollough effect can turn their head or rotate an image upside-down, but the effect remains unchanged in orientation.

The full reasons behind the McCollough effect are still unknown. It’s clear that it isn’t just simple neural fatigue; the brain is somehow rewired to associate dark edges with the new colours. 

To reiterate, this probably isn’t something you should mess around with. It’s something that can change the way your brain works for a long time – and that’s a scary prospect indeed.