What is an Optical Illusion?

An optical illusion is a visual phenomenon where the eye perceives something different from physical reality. Illusions can involve color, movement, size, or spatial relationships, exploiting quirks in human visual processing. Surrealists were fascinated by optical illusions as evidence that perception cannot be trusted and that reality is more unstable than it appears. Salvador Dali created double images that shift between interpretations, while artists like M.C. Escher (influenced by Surrealism) created impossible architectures. Understanding how illusions work illuminates Surrealism’s broader interest in the uncanny and destabilized perception. Related techniques include trompe-l’oeil.