Here’s why you can’t see all twelve black dots in this optical illusion

Optical illusions have a way of breaking the internet, and the latest visual trick looks like it’s well on its way. On Sunday afternoon, game developer Will Kerslake tweeted a picture of intersecting gray lines on a white background. Twelve black dots blink in and out of existence where the gray lines meet. In the six hours since he posted the photo to Twitter, it’s been shared more than 6,000 times, with commenters demanding to know why they can’t see all twelve dots at the same time.

The optical illusion was first posted to Facebook about a day ago by Japanese psychology professor Akiyoshi Kitaoka, and it has been shared more than 4,600 times so far. But the origin of this bit of visual trickery is a scientific paper published in the...