Kanizsa Triangle

What do you see?

A bright white triangle pointing upward, with sharp edges, sitting on top of three black discs and an outlined triangle pointing down. The white triangle even looks a little brighter than the white page around it. Press Reveal to rotate the discs: the triangle disappears, because it was never drawn.

How it works

The Kanizsa triangle is the classic example of illusory contours: edges that you see clearly even though there is no change in brightness or colour along them. Your brain creates the triangle because it is the simplest explanation for the picture.

Consider the alternatives. The image could be three black shapes with wedges cut out of them, plus three disconnected pairs of lines, all arranged by coincidence so that every gap lines up perfectly. Or it could be a white triangle lying on top of three complete black discs and a complete outlined triangle, partly hiding them. The visual system strongly prefers the second explanation, because coincidences like that rarely happen in the real world, while objects overlapping each other happen constantly.

Once the occluding triangle is accepted, the brain fills in its missing edges between the corners. Neurons in visual area V2, and to a lesser extent V1, have been found to respond to illusory contours as if a real edge were present. That suggests the edge is constructed early in visual processing, not merely imagined or inferred at a later stage.

The extra brightness is a further clue. The illusory triangle often looks whiter than the background, even though they are identical. One explanation is that the brain assigns the surface to a separate object in front, and brightness is computed per surface. Another is that contrast with the black inducers is spread across the whole surface of the triangle. Either way, the white region is not just bounded but filled.

The figure needs precise alignment. Rotate the discs a little and the triangle disappears, as the reveal shows. Make the wedges smaller and the triangle fades. Make the discs bigger and closer, and it gets stronger. These rules help scientists understand how the brain decides which edges belong together.

Illusory contours are not just a laboratory curiosity. Camouflage, partly hidden objects and logos such as the arrow hidden in some company names rely on the same tendency to complete shapes that are not fully drawn.

History

Italian psychologist Gaetano Kanizsa published the figure in 1955. Illusory contours had been noted earlier, for example by Friedrich Schumann in 1900, but Kanizsa's triangle made the phenomenon famous and became a central example in Gestalt psychology. This drawing was made for OpticalIllusions.com.

Try it

• Press Reveal to rotate the discs and lose the triangle.
• Cover two of the discs with your fingers: the triangle edges near them disappear.
• Look at the centre of the triangle and ask whether it seems brighter than the page.
• Draw your own version with coins and paper wedges.

Written by K.R. for OpticalIllusions.com · Updated October 26, 2026. Illusion artwork © The Wizard Of Sales, LLC. Feel free to share a link; see our terms for reuse.