Delboeuf illusion

The Delboeuf illusion is an optical illusion of relative size perception. In the best-known version of the illusion, two circles of identical size have been placed near to each other and one is surrounded by an annulus; the surrounded circle then appears larger than the non-surrounded circle if the annulus is close, while appearing smaller than the non-surrounded circle if the annulus is distant. A 2005 study suggests it is caused by the same visual processes that cause the Ebbinghaus illusion.[1]


It was named for the Belgian philosopher, mathematician, experimental psychologist, hypnotist and psychophysicist Joseph Remi Leopold Delboeuf (1831–1896), who created it in 1865.[2]

A debunked research study related to the Delboeuf illusion claimed that eating off small plates tricks diners into eating less. In June 2018, researchers at Israel's Ben-Gurion University of the Negev published a paper calling the claim into question.[3]


  1. Roberts B, Harris MG, Yates TA (2005). "The roles of inducer size and distance in the Ebbinghaus illusion (Titchener circles)". Perception. 34 (7): 847–56. doi:10.1068/p5273. PMID 16124270.
  2. Delboeuf, Franz Joseph (1865). "Note sur certaines illusions d'optique: Essai d'une théorie psychophysique de la maniere dont l'oeil apprécie les distances et les angles". Bulletins de l'Académie Royale des Sciences, Lettres et Beaux-arts de Belgique. 19: 195–216.
  3. "The Delboeuf Illusion: Common Weight Loss Trick Debunked in Study". 2018-07-17. Retrieved 2018-07-18.

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