Ehrenstein illusion

The Ehrenstein illusion is an optical illusion studied by the German psychologist Walter Ehrenstein (1899 1961) in which the sides of a square placed inside a pattern of concentric circles take an apparent curved shape (Figure 1).[1][2]

Sometimes the name "Ehrenstein" is associated with one of the illusory contour figures (Figure 2).[3][4][5] The ends of the dark segments produce the illusion of circles. The apparent figures have the same color as the background, but appear brighter. A similar effect is obtained in the Kanizsa triangle.


  1. A catalogue of illusions at Ritsumeikan University
  2. W. Ehrenstein (1925). "Versuche über die Beziehungen zwischen Bewegungs- und Gestaltwahrnehmung" [Experiments on the Relationships Between the Perception of Motion and of Gestalt]. Zeitschrift für Psychologie. 96: 305–352.
  3. Ehrenstein illusion at Scholarpedia
  4. W. Ehrenstein (1941). "Über Abwandlungen der L. Hermannschen Helligkeitserscheinung". Zeitschrift für Psychologie. 150: 83–91.
  5. W. Ehrenstein (1954). Probleme der ganzheitspsychologischen Wahrnehmungslehre. Leipzig: Barth.

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