Müller-Lyer Illusion (1889)
The two horizontal lines are identical in length, yet the one with outward-pointing arrowheads appears longer. The brain uses arrow direction as a depth cue — outward fins suggest a far corner (longer), inward fins a near corner (shorter). Toggle Reveal geometry to show the true measurements.
The two horizontal lines are identical in length, yet the one with outward-pointing arrowheads appears longer. The brain uses arrow direction as a depth cue — outward fins suggest a far corner (longer), inward fins a near corner (shorter). Toggle Reveal geometry to show the true measurements.