Two orange circles. One looks bigger. See how strongly your brain fools you.
Interactive · Try it in the app
Your guess
Which orange circle is bigger?
Not quite.
Same size – down to the pixel. Small neighbors make the left one look bigger, large neighbors make the right one look smaller. Your brain judges size by comparison.
Not everyone sees it the same
The larger a person's primary visual cortex, the weaker the illusion, a London team found. And Himba children, who live remotely in Namibia, didn't see it at all until the age of nine or ten. British children did by seven or eight.
Fits with this
Nº 012 · Perception · 1 min
There's a hole in your field of view.
Every eye has a blind spot. You've never noticed yours – your brain simply paints it over.
Nº 013Interactive
Nº 013 · Physics · 55 sec
Why does metal feel colder than wood?
Even though both are exactly the same temperature. Your skin doesn't measure temperature at all.
