Visually perceived images that differ from objective reality
This article is about visual perception. For the album, see Optical Illusion (album). For the film, see Optical Illusions (film).
The checker shadow illusion. Although square A appears a darker shade of gray than square B, in the image the two have exactly the same luminance.
Drawing a connecting bar between the two squares breaks the illusion and shows that they are the same shade.
In visual perception, an optical illusion (also called a visual illusion[2]) is an illusion caused by the visual system and characterized by a visual percept that arguably appears to differ from reality. Illusions come in a wide variety; their categorization is difficult because the underlying cause is often not clear[3] but a classification[1][4] proposed by Richard Gregory is useful as an orientation. According to that, there are three main classes: physical, physiological, and cognitive illusions, and in each class there are four kinds: Ambiguities, distortions, paradoxes, and fictions.[4] A classical example for a physical distortion would be the apparent bending of a stick half immerged in water; an example for a physiological paradox is the motion aftereffect (where, despite movement, position remains unchanged).[4] An example for a physiological fiction is an afterimage.[4] Three typical cognitive distortions are the Ponzo, Poggendorff, and Müller-Lyer illusion.[4] Physical illusions are caused by the physical environment, e.g. by the optical properties of water.[4] Physiological illusions arise in the eye or the visual pathway, e.g. from the effects of excessive stimulation of a specific receptor type.[4] Cognitive visual illusions are the result of unconscious inferences and are perhaps those most widely known.[4]
Pathological visual illusions arise from pathological changes in the physiological visual perception mechanisms causing the aforementioned types of illusions; they are discussed e.g. under visual hallucinations.
Optical illusions, as well as multi-sensory illusions involving visual perception, can also be used in the monitoring and rehabilitation of some psychological disorders, including phantom limb syndrome[5] and schizophrenia.[6]
^ abGregory, Richard (1991). "Putting illusions in their place". Perception. 20 (1): 1–4. doi:10.1068/p200001. PMID 1945728. S2CID 5521054.
^In the scientific literature the term "visual illusion" is preferred because the older term gives rise to the assumption that the optics of the eye were the general cause for illusions (which is only the case for so-called physical illusions). "Optical" in the term derives from the Greek optein = "seeing", so the term refers to an "illusion of seeing", not to optics as a branch of modern physics. A regular scientific source for illusions are the journals Perception and i-Perception
^Bach, Michael; Poloschek, C. M. (2006). "Optical Illusions" (PDF). Adv. Clin. Neurosci. Rehabil. 6 (2): 20–21. Archived from the original (PDF) on 2021-01-20. Retrieved 2017-12-29.
^ abcdefghGregory, Richard L. (1997). "Visual illusions classified" (PDF). Trends in Cognitive Sciences. 1 (5): 190–194. doi:10.1016/s1364-6613(97)01060-7. PMID 21223901. S2CID 42228451.
^DeCastro, Thiago Gomes; Gomes, William Barbosa (2017-05-25). "Rubber Hand Illusion: Evidence for a multisensory integration of proprioception". Avances en Psicología Latinoamericana. 35 (2): 219. doi:10.12804/revistas.urosario.edu.co/apl/a.3430. ISSN 2145-4515.
^King, Daniel J.; Hodgekins, Joanne; Chouinard, Philippe A.; Chouinard, Virginie-Anne; Sperandio, Irene (2017-06-01). "A review of abnormalities in the perception of visual illusions in schizophrenia". Psychonomic Bulletin & Review. 24 (3): 734–751. doi:10.3758/s13423-016-1168-5. ISSN 1531-5320.
In visual perception, an opticalillusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual percept...
Archived from the original on 13 July 2019. Retrieved 10 May 2015. "Opticalillusion: Dress color debate goes global". BBC News. BBC. Archived from the...
generally shared by most people. Illusions may occur with any of the human senses, but visual illusions (opticalillusions) are the best-known and understood...
The Moon illusion is an opticalillusion which causes the Moon to appear larger near the horizon than it does higher up in the sky. It has been known...
The Great Illusion is a book by Norman Angell, first published in the United Kingdom in 1909 under the title Europe's OpticalIllusion and republished...
The checker shadow illusion is an opticalillusion published by Edward H. Adelson, professor of vision science at MIT, in 1995. The image depicts a checkerboard...
Phantogram may refer to: Phantogram (band) Phantogram (opticalillusion) Phantagram South Korean video game maker This disambiguation page lists articles...
The Jastrow illusion is an opticalillusion attributed to the Polish-American psychologist Joseph Jastrow. This opticalillusion is known under different...
Op art, short for optical art, is a style of visual art that uses opticalillusions. Op artworks are abstract, with many better-known pieces created in...
the scintillating grid illusion. The Hermann grid illusion is an opticalillusion reported by Ludimar Hermann in 1870. The illusion is characterized by "ghostlike"...
hill, is a place where the layout of the surrounding land produces an opticalillusion, making a slight downhill slope appear to be an uphill slope. Thus...
in 1973, gradually expanding to become an award-winning complex of opticalillusions and puzzling rooms and the world's first 3-D maze. Puzzling World...
spiral illusion is an opticalillusion that was first described by the British psychologist Sir James Fraser (1863–1936) in 1908. The illusion is also...
are unexplained phenomena that could have an optical explanation and "opticalillusions" for which optical explanations have been excluded. There are many...
one for the angle of orientation of the astigmatism. Opticalillusions (also called visual illusions) are characterized by visually perceived images that...
The Necker cube is an opticalillusion that was first published as a rhomboid in 1832 by Swiss crystallographer Louis Albert Necker. It is a simple wire-frame...
An Ames room is a distorted room that creates an opticalillusion. Likely influenced by the writings of Hermann Helmholtz, it was invented by American...
The Ebbinghaus illusion or Titchener circles is an opticalillusion of relative size perception. Named for its discoverer, the German psychologist Hermann...
known as an impossible figure or an undecidable figure) is a type of opticalillusion that consists of a two-dimensional figure which is instantly and naturally...
Auditory illusions are false perceptions of a real sound or outside stimulus. These false perceptions are the equivalent of an opticalillusion: the listener...
it is actually the Earth's motion that causes the Sun to appear. The illusion of a moving Sun results from Earth observers being in a rotating reference...
Dewanpatpar magnetic hill, 40 km north of Pandariya, which has an opticalillusion of a gravity hill where vehicle seems to defy the gravity and roll...