The two orange circles are the same size, but the one on the left, ringed by large circles, looks smaller.
Try this
- Shrink Size of the outer circles: the left circle seems to grow.
- Change How many to see whether more neighbors make it stronger.
- Tick Hide the outer circles to compare them directly.
Why it happens
Your brain judges size partly by comparison. Next to big neighbors the center circle looks small; next to small ones it looks big. Distance matters too: when the surrounding circles are close to the center one, they can make it look bigger, and when they are far away the size contrast wins. Brian Roberts, Mike Harris and Tim Yates showed that the size of the surrounding circles and their distance both change the strength of the effect.
Interestingly, studies have found that when people reach out to grab disks arranged like this, their grip often matches the real size better than their eyes do, one of the clues that perception and action use vision in different ways.
Did you know?
It is named after Hermann Ebbinghaus, the German psychologist better known for his research on memory, and is also called Titchener circles after the psychologist who popularized it.
References
- Roberts B., Harris M., Yates T. (2005). The Roles of Inducer Size and Distance in the Ebbinghaus Illusion (Titchener Circles). Perception, 34, 847-856. doi:10.1068/p5273
- Background on Wikipedia
The illusion on this page is drawn by code written for this site. Last checked 1 November 2026.
Frequently asked questions
Are the orange circles the same size?
Yes, exactly the same. Hide the outer circles to check.
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