Hidden Circles

What is happening

At first this looks like a grid of rectangles, alternating between vertical and horizontal stripes. Keep looking and, for some people, round shapes emerge near the corners of the rectangles. The circles in this figure have no outline at all — only the stripe direction changes inside each one, so the “boundary between directions” reads as a circle.

Why it looks that way

The visual system treats a stretch of stripes running the same way as one continuous surface. In this figure, the rectangle boundaries are straighter and more numerous, so they get grouped first. The circle boundaries are built from the same cue — a change in stripe direction — but they overlap the rectangle corners and get broken up, so they’re harder to pick out as shapes. Once you notice a circle, the circles can start to stand out more than the rectangles.

How to check

Try stepping back from the screen, squinting, or shrinking the image, and see whether what you notice changes. Revealing the answer overlays a colored outline on each circle’s position. Finding fewer of them says nothing about how good your eyes are.

First described

After Anthony Norcia

Known as a pattern of rectangles resembling a coffered ceiling, with circles hidden inside it. This site’s figure re-implements the stripe-panel and circle layout independently.

See it in the timeline