Beware! Don’t stare at the image in this video if you’re worried about rewiring your brain.
Called the McCollough effect, it involves staring at images of vertical and horizontal lines, and it can make black and white look like green and red for up to three and a half months.
The effect was first discovered by American psychologist Celeste McCollough Howard in 1965, and explained by YouTube user Tom Scott on his channel Things You Might Not Know.
To befuddle your brain, first look at a test grid image of black and white horizontal and vertical lines to confirm they appear black and white.
Next, you must stare alternately at a square containing horizontal red and black stripes, and then a vertical green equivalent for up to three minutes – alternating between staring at the centre of both for several seconds.
Once this is done, stare back at the original grid image of black and white gratings.
Now, instead of appearing black and white, the top right and bottom left vertical gratings will have a pinkish hue, while the top left and bottom right horizontal gratings will appear slightly green.