Stare at the above image long enough and you’ll start to notice something peculiar: When your eyes focus on one of the gray intersections in the picture, two or three black dots will appear. But as you hold your gaze, the dots in your periphery seem to fade from view, and if your direct your vision elsewhere, they’ll hop to a different area altogether.

This optical illusion has been baffling the internet since it was shared by Japanese psychology professor Akiyoshi Kitaoka on Sunday, September 11. Most people are incapable of seeing all 12 black dots in the image at once, a phenomenon The Verge reports is due to humans’ poor peripheral vision.

Because our eyes can’t process the visual information in our peripheries as well as what’s directly in front of us, our brains make guesses with what's available to fill in any mental gaps, according to researchers who first introduced the world to the illusion. So when we stare at a black dot surrounded by a pattern of gray lines against a white background, our mind assumes what the intersection of the gray lines will look like without adding a black dot in the center.

A paper published in 2000 in the journal Perception, where the optical illusion first appeared, explains how our brains react to the image:

“When the white disks in a scintillating grid are reduced in size, and outlined in black, they tend to disappear. One sees only a few of them at a time, in clusters which move erratically on the page. Where they are not seen, the grey alleys seem to be continuous, generating grey crossings that are not actually present.”

Seeing objects in our periphery isn't the only task the human eye struggles with. The imperfect way we process color also makes for some mind-bending optical illusions.

[h/t The Verge]

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