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Encyclopedia > Visual illusions

An optical illusion is any illusion that deceives the human visual system into perceiving something that is not present or incorrectly perceiving what is present. There are physiological illusions and cognitive illusions. Optical illusions can naturally happen by specific optical tricks that show particular assumptions in the human perceptual system. An illusion is a distortion of a sensory perception. ... The visual system is what allows us to see. ... PSYCHOLOGY In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ...

An optical illusion. Square A is exactly the same shade of grey as square B
An optical illusion. Square A is exactly the same shade of grey as square B
The Scintillating grid illusion. Black spots seem to appear and disappear very fast at the intersections
The Scintillating grid illusion. Black spots seem to appear and disappear very fast at the intersections
Simultaneous Contrast Illusion. The grey bar is the same shade throughout
Simultaneous Contrast Illusion. The grey bar is the same shade throughout
Penrose triangle
Penrose triangle
An optical illusion. The two circles seem to move when the head is moving forwards and backwords
An optical illusion. The two circles seem to move when the head is moving forwards and backwords

A mirage is a natural illusion that is an optical phenomenon. The variation in the apparent size of the Moon (smaller when overhead, larger when near the horizon) is another natural illusion; it is not an optical phenomenon, but rather a cognitive or perceptual illusion. Prepared for Wikipedia by Adrian Pingstone in January 2004, based on the original created by Edward H. Adelson. ... Prepared for Wikipedia by Adrian Pingstone in January 2004, based on the original created by Edward H. Adelson. ... Download high resolution version (2048x2048, 11 KB) The Scintillating grid illusion. ... Download high resolution version (2048x2048, 11 KB) The Scintillating grid illusion. ... The Scintillating grid illusion A grid illusion is any kind of grid illusion that deceives a persons vision. ... Simultaneous Contrast Illusion. ... Simultaneous Contrast Illusion. ... Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... A road mirage, a type of inferior mirage A mirage is an optical phenomenon which often occurs naturally. ... An optical phenomenon is any observable event which results from the interaction of light and matter. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... The term cognition is used in several different loosely related ways. ... PSYCHOLOGY In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ...


Developed illusions include phenomena such as the Necker cube and the Scintillating/Hermann grid. They could also be called discovered illusions. Understanding these phenomena is useful in order to understand the limitations of the human visual system. The Necker Cube is an optical illusion first published in 1832 by Swiss crystallographer Louis Albert Necker. ... The Scintillating grid illusion A grid illusion is any kind of grid illusion that deceives a persons vision. ...


Physiological illusions, such as the afterimages following bright lights or adapting stimuli of excessively longer alternating patterns (contingent perceptual aftereffect, CAE), are the effects on the eyes or brain of excessive stimulation of a specific type - brightness, tilt, colour, movement, and so on. The theory is that stimuli have individual dedicated neural paths in the visual outer wall of an organism for the early stages of visual processing; repetitive stimulation of only a few channels misleads the visual system. An afterimage is an optical illusion that occurs after looking away from a direct gaze at an image. ...


Cognitive illusions are more interesting and well-known. Instead of demonstrating a physiological base they interact with different levels of perceptual processing, in-built assumptions or 'knowledge' are misdirected. Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions. They often exploit the predictive hypotheses of early visual processing. Stereograms are based on a cognitive visual illusion. The term stereogram may also refer to an old type of integrated high fidelity system or music centre. ...


Ambiguous illusions are pictures or objects that offer significant changes in appearance. Perception will 'switch' between the alternates as they are considered in turn as available data does not confirm a single view. The Necker cube is a well known example, the motion parallax due to movement is being misinterpreted, even in the face of other sensory data. Another popular is the Rubin vase. The Necker Cube is an optical illusion first published in 1832 by Swiss crystallographer Louis Albert Necker. ...


Distorting illusions are the most common, these illusions offer distortions of size, length, or curvature. They were simple to discover and are easily repeatable. Many are physiological illusions, such as the Cafe wall illusion which exploits the early visual system encoding for edges. Other distortions, such as converging line illusions, are more difficult to place as physiological or cognitive as the depth-cue challenges they offer are not easily placed. All pictures that have perspective cues are in effect illusions. Visual judgements as to size are controlled by perspective or other depth-cues and can easily be wrongly set. The caf wall illusion The caf wall illusion is an optical illusion, first described by Doctor Richard Gregory. ...


Paradox illusions offer objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircases seen, for example, in the work of M. C. Escher. The triangle is an illusion dependent on a cognitive misunderstanding that adjacent edges must join. They occur as a byproduct of perceptual learning. The Penrose triangle The Penrose triangle, also known as the tribar is an impossible object. ... The Penrose stairs is an impossible object devised by Lionel Penrose and his son Roger Penrose and can be seen as a variation on his Penrose triangle. ... Self portrait, 1943¹ Maurits Cornelis Escher (Leeuwarden, June 17, 1898 - Laren, March 27, 1972) was a Dutch artist most known for his woodcuts, lithographs and mezzotints, which tend to feature impossible constructions, explorations of infinity, and tessellations. ...


Fiction illusions are the perception of objects that are genuinely not there to all but a single observer, such as those induced by schizophrenia or hallucinogenic drugs. Hallucinogenic drugs or hallucinogens are drugs that can alter sensory perceptions, elicit alternate states of consciousness, or cause hallucinations. ...


Known illusions include:

Many artists have worked with optical illusions, some extensively, including M.C. Escher, Salvador Dalí, Giuseppe Arcimboldo, Marcel Duchamp, Oscar Reutersvärd and anyone who has ever worked with perspective. An Ames room is a distorted room that is used to create an optical illusion. ... Benhams top, also called Benhams disk, is named after the English toymaker Charles Benham, who, in 1895, sold a top painted with the pattern shown. ... The Bezold Effect is an optical illusion, named after a German professor of meteorology, Wilhelm von Bezold (1837-1907), who discovered that a colour may appear different depending on its relation to adjacent colours. ... The caf wall illusion The caf wall illusion is an optical illusion, first described by Doctor Richard Gregory. ... The Craik-OBrien-Cornsweet illusion, also known as the Craik-Cornsweet illusion and the Cornsweet illusion, was discovered by Tom Cornsweet in the late 1960s. ... Categories: Optical illusions ... The Fraser spiral illusion is the famous spiral after-effect optical illusion based on the motion after-effect illusion. ... Categories: Optical illusions ... The Scintillating grid illusion A grid illusion is any kind of optical illusion that deceives a persons vision. ... This blivet is reminiscent of an M.C. Escher painting--it portrays two impossible perspectives at once, creating a lost layer between the top two rods, and an impossible extra, vanishing rod in between the bottom two. ... [Image:http://i. ... Categories: Optical illusions ... Categories: Optical illusions ... A Mach band is an optical illusion, named after Ernst Mach. ... The missing square puzzle is an optical illusion used in mathematics classes, to help students reason about geometrical figures. ... The moon illusion is an optical illusion in which the moon appears larger near the horizon than it does while higher up in the sky. ... The motion aftereffect (MAE) is a visual illusion perceived after watching a moving visual stimulus for several seconds and then looking at stationary stimulus. ... Categories: Optical illusions ... Wikipedia does not have an article with this exact name. ... The Mueller-Lyer illusion is a famous distortion optical illusion consisting of nothing more than an arrow. ... The Necker Cube is an optical illusion first published in 1832 by Swiss crystallographer Louis Albert Necker. ... The Penrose triangle The Penrose triangle, also known as the tribar is an impossible object. ... The phi phenomenon is a perceptual illusion described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion, in which a disembodied perception of motion is produced by a succession of still images. ... The Poggendorf Illusion is an optical illusion that involves the brains perception of the interaction between diagonal lines and horizontal and vertical edges. ... Stereoscopy, stereoscopic imaging or 3-D (three-dimensional) imaging is a technique to create the illusion of depth in a photograph, movie, or other two-dimensional image, by presenting a slightly different image to each eye. ... Categories: Optical illusions ... The Scintillating grid illusion A grid illusion is any kind of optical illusion that deceives a persons vision. ... Demonstration Say the color of these words as fast as you can: According to the Stroop effect, the first set of colors would have had a faster reaction time. ... Whites illusion is an optical illusion illustrating the fact that the same target luminance can elicit different perceptions of brightness in different contexts. ... Categories: Optical illusions ... Categories: Optical illusions ... Self-portrait (1943) by M.C. Escher Maurits Cornelis Escher (Leeuwarden, June 17, 1898 – March 27, 1972 in Laren) was a Dutch mathematical artist known for his woodcuts, lithographs and mezzotints which feature impossible constructions, explorations of infinity, and tessellations. ... Salvador Dalí as photographed in 1934 by Carl Van Vechten Salvador Felip Jacint Dalí Domènech (May 11, 1904 – January 23, 1989) was an important Catalan-Spanish painter, best known for his surrealist works. ... Vertemnus, a portrait of Rudolf II Giuseppe Arcimboldo (1527 in Milan, Italy - 1593) was a distinctive and eccentric painter who is best known for creating portrait heads made entirely of such objects as fruit or vegetables or flowers, or fish, or inanimate objects such as books -- that is, he painted... Marcel Duchamp (July 28, 1887 – October 2, 1968) was an influential French/American artist. ... The Stockholm-born artist Oscar Reutersvärd (1915–2002), the father of the impossible figure, pioneered the art of impossible objects. ...


Optical illusion is also used in film by the technique of forced perspective. Forced perspective is a filmmaking technique to make larger objects appear smaller to the viewer or vice versa, depending on their relationship to the camera and each other. ...


References

See also

Alice in Wonderland syndrome (AIWS), or micropsia, is a disorienting neurological condition which affects human visual perception. ... An auditory illusion is an illusion of hearing (sense), the sound equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or impossible sounds. ... A fata Morgana, named after Morgan le Fay, the faery shapeshifting half-sister of King Arthur, is a mirage, an optical phenomenon which results from a temperature inversion. ... A gravity hill (also known as a gravity road) is a place where the layout of the surrounding land produces the optical illusion that a very slight downhill slope is in fact an uphill slope. ... Hermann von Helmholtz Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist. ... Professor Horace Basil Barlow FRS (born December 8, 1921) is a visual neuroscientist. ... Two famous undecidable figures, the Penrose triangle and devils pitchfork An impossible object is an object that cannot exist according to the known laws of nature, but has a description or representation suggesting, at first sight, that it can. ... Op art is a term used to described certain paintings made primarily in the 1960s which exploit the fallibilty of the eye through the use of optical illusions. ... Examples of visually ambiguous patterns. ... The reverse rotation effect is an optical illusion caused by spoked wheels which appear to rotate backwards when reaching a certain velocity. ... The term adaptation when used within the context of the biology of the eye refers to its ability to adjust to various levels of darkness and light. ...

External links


  Results from FactBites:
 
The Principles of Artistic Illusions (3200 words)
It is a close relative of the "Ponzo Illusion".
This is an illusion of relative dimensions within a picture, which is a distortion of shape.
It may be that the appreciation of such visual paradoxes is one sign of that kind of creativity possessed by the best mathematicians, scientists and artists.
  More results at FactBites »

 
 

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