Oppel-Kundt illusion

The part of the figure filled with some elements (upper, discretely; lower, continuously) seems longer than the unfilled part of the same length

The Oppel-Kundt illusion is a geometric optical illusion that occurs when comparing the sizes of filled (with some visual elements, distractors) and unfilled parts of the image (for most observers, the filled part seems larger). The illusion is named after German physicists Johann Joseph Oppel [de] (first mentioned this phenomenon in 1860) and August Kundt (first performed a systematic study of the illusion in 1863). It is also known as the "filled-space illusion" or the "illusion of interrupted extent".[1][2] Depending on the filling elements used, there is a wide variety of graphic implementations of the Oppel-Kundt illusion, which also differ in the magnitude of the visual distortion effects they cause.

  1. ^ Lewis, E. O. (March 1912). "The Illusion of Filled and Unfilled Space". British Journal of Psychology. 5 (1): 36–50. doi:10.1111/j.2044-8295.1912.tb00054.x.
  2. ^ Luckiesh, M. (1922). Visual illusions, their causes, characteristics and applications. New York: D. Van Nostrand Company. LCCN 22003634. OCLC 271206850 – via HathiTrust.