"Filling In"

What do you see? 

Four circular shapes, all missing quarter sections, which when stacked seem to produce a square from the negative space.

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You might think you’re seeing a square or four circles. But in fact, there is not a single complete square or circle!

"Four circles, all missing a quarter section, rotating"

So, what makes you see those shapes? When an image is incomplete, your brain fills in the gaps by figuring out the most likely interpretation. This helps you quickly make decisions. Usually, your brain is right. But this time, it made you see something that isn’t there.

Check out another illusion like this one!

Look at the scene. Is it moving or staying still?

Interior view of a donut-shaped room, patterned with orange dots over a purple background. The pattern creates the illusion that the room is turning.

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If the scene appears to be moving, then your brain’s being tricked!

The illusion is triggered by eye movements. Even when you stare at a still object, your eyes dart around. Normally, your brain can tell the difference between your eyes moving and an object moving. But because of the strong contrasts and shapes in the illusion, your brain gets confused. Your motion sensors switch on, and the image seems to turn.

Your brain evolved to focus attention on movement because it can be a sign of danger. But in the case of this image, the movement you see is an illusion created in your mind!

Next, find out how different factors influence what you see.

Image Credits:
© AMNH; patterned donut-shaped room, © Beau Deeley.