Open Science Tools / Pavlovia
3 minutes
The Müller-Lyer Illusion: Arrowheads Distort Perceived Length
In the Müller-Lyer illusion a line ending in inward-pointing arrowheads appears longer than an equal line ending in outward-pointing ones. The effect persists when the viewer knows the lines are equal, showing that perception is computed from context rather than read directly from the stimulus. Adjusting one line until the two look equal gives a numerical illusion magnitude that varies across people and conditions.