This pattern changes as it gets closer to your face

Try holding the shapes steady. You can't!
head trip pattern
tk PopSci

We know you are bored at home right now—we are too. Here are some puzzles and brainteasers to challenge your family and friends with, either in person or over video chat.

Sometimes the farther away you are from something, the clearer it is. At a distance, you can tell that the pattern in the center of this image differs slightly from the design around it. But get close to the screen, and one pattern appears to overtake the other, making the once-disparate motifs suddenly match.

Known as the uniformity illusion, which University of Amsterdam assistant professor Yair Pinto first described in 2016, this sleight takes advantage of the way we gather information through our eyeballs.

In the center of the eye sits a tiny pit known as the fovea. It contains a high density of retinal cones, which provide a detailed and colorful impression of the objects directly in front of us. By contrast, images at the edge of our gaze are perceived by peripheral vision, which receives information primarily from rods that are worse than cones at detecting shapes and colors.

This outlying vision is always pretty weak. But it becomes increasingly unreliable the closer the eye gets to a scene. That might explain why we can make out the shapes OK from afar, but when we stick our faces too close to the page, things get muddled and the brain must make a judgment call. Since the fovea is usually more dependable, we assume whatever’s going on along the edges is an “input error,” Pinto says, and try to match every design to the one in the center.

This works with all sorts of visual alterations. If the inside pattern is clear but the outer one is blurry, the uniformity illusion can cause the whole image to appear perfectly crystalline. The same is true not just for shapes, but also for mismatched text, altered orientation, and even changes in an image’s density—look too close, and the outer pattern will match whatever is in the inside. No matter how weird things get, the brain will rely on the best signal it has, Pinto says. That doesn’t always guarantee the correct answer (clearly). So it’s best to get some perspective.

This story originally published in the Out There issue of Popular Science.