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An optical illusion. Square A is exactly the same shade of grey as square B. See Same color illusion
An optical illusion. Square A is exactly the same shade of grey as square B. See Same color illusion
This article is about visual perception. The same color illusion — also known as Adelson's checker shadow illusion, checker shadow illusion and checker shadow — is an Optical illusion See Optical Illusion (Album) for information about the Time Requiem album. This article is about the Time Requiem album See Optical illusion for information about visually perceived images

An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also The information gathered by the eye is processed by the brain to give a percept that does not tally with a physical measurement of the stimulus source. A perception is a philosophical term which roughly means an individual's observation/perception of something external to one's self more specifically the resultant of perceiving There are three main types of illusion - literal optical illusions that create images that are different from the objects that make them, physiological illusions that are the effects on the eyes and brain of excessive stimulation of a specific type - brightness, tilt, color, movement, and cognitive illusions where the eye and brain make unconscious inferences. Cognition is a concept used in different ways by different disciplines but is generally accepted to mean the process of awareness or thought

Contents

Physiological illusions

A scintillating grid illusion. Shape position and colour contrast converge to produce the illusion of grey dots at the intersections.
A scintillating grid illusion. A grid illusion is any kind of Grid that deceives a person's vision Shape position and colour contrast converge to produce the illusion of grey dots at the intersections. Contrast is the difference in visual properties that makes an object (or its representation in an image distinguishable from other objects and the background

Physiological illusions, such as the afterimages following bright lights or adapting stimuli of excessively longer alternating patterns (contingent perceptual aftereffect), are presumed to be the effects on the eyes or brain of excessive stimulation of a specific type - brightness, tilt, color, movement, etc. An afterimage or ghost image is an Optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased The theory is that stimuli have individual dedicated neural paths in the early stages of visual processing, and that repetitive stimulation of only one or a few channels causes a physiological imbalance that alters perception. Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical

The Hermann grid illusion and Mach bands are two illusions that are best explained using a biological approach. A grid illusion is any kind of Grid that deceives a person's vision Mach bands are an Optical illusion consisting of an image of two wide bands one light and one dark separated by a narrow strip with a light-to-dark gradient Lateral inhibition, where in the receptive field of the retina light and dark receptors compete with one another to become active, has been used to explain why we see bands of increased brightness at the edge of a color difference when viewing Mach bands. In Neurobiology, lateral inhibition is the capacity of an excited Neuron to reduce the activity of its neighbors The receptive field of a sensory Neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron Once a receptor is active it inhibits adjacent receptors. This inhibition creates contrast, highlighting edges. In the Hermann grid illusion the grey spots appear at the intersection because of the inhibitory response which occurs as a result of the increased dark surround. [1] Lateral inhibition has also been used to explain the Hermann grid illusion, but this has been disproved. In Neurobiology, lateral inhibition is the capacity of an excited Neuron to reduce the activity of its neighbors A grid illusion is any kind of Grid that deceives a person's vision A grid illusion is any kind of Grid that deceives a person's vision

Ambiguous illusions

Cognitive illusions are assumed to arise by interaction with assumptions about the world, leading to "unconscious inferences", an idea first suggested in the 19th century by Hermann Helmholtz. Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions.

  1. Ambiguous illusions are pictures or objects that elicit a perceptual 'switch' between the alternative interpretations. The Necker cube is a well known example; another instance is the Rubin vase. The Necker Cube is an Optical illusion first published in 1832 by Swiss Crystallographer Louis Albert Necker. Rubin's vase (sometimes known as the Rubin face or the Figure-ground vase) is a famous set of cognitive
  2. Distorting illusions are characterized by distortions of size, length, or curvature. A striking example is the Café wall illusion. The café wall illusion is an Optical illusion, first described by Richard Gregory in 1973 Another example is the famous Müller-Lyer illusion. The Müller-Lyer illusion is an Optical illusion consisting of nothing more than an arrow
  3. Paradox illusions are generated by objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircases seen, for example, in M. C. Escher's Ascending and Descending and Waterfall. The Penrose triangle, also known as the tribar, is an Impossible object. The Penrose stairs is an Impossible object created by Lionel Penrose and his son Roger Penrose. Maurits Cornelis Escher (17 June 1898 – 27 March 1972 usually referred to as M Ascending and Descending is a lithograph print by the Dutch artist M Waterfall is a lithograph print by the Dutch artist M C Escher which was first printed in October 1961. The triangle is an illusion dependent on a cognitive misunderstanding that adjacent edges must join.
  4. Fictional illusions are defined as the perception of objects that are genuinely not there to all but a single observer, such as those induced by schizophrenia or a hallucinogen. Observation is either an activity of a living being (such as a Human) which senses and assimilates the Knowledge of a Phenomenon, or the recording of data Schizophrenia ( from the Greek roots schizein (σχίζειν "to split" and phrēn The general group of pharmacological agents commonly known as hallucinogens can be divided into three broad categories Psychedelics, Dissociatives These are more properly called hallucinations. A hallucination, in the broadest sense is a Perception in the absence of a stimulus.

Explanation of cognitive illusions

Perceptual organization

Reversible figure and vase
Reversible figure and vase
Duck-Rabbit illusion
Duck-Rabbit illusion
My Wife and My Mother-In-Law
My Wife and My Mother-In-Law

To make sense of the world it is necessary to organize incoming sensations into information which is meaningful. Gestalt psychologists believe one way this is done is by perceiving individual sensory stimuli as a meaningful whole. [2] Gestalt organization can be used to explain many illusions including the Duck-Rabbit illusion where the image as a whole switches back and forth from being a duck then being a rabbit and why in the figure-ground illusion the figure and ground are reversible. In Visual perception, figure-ground is a type of Perceptual organization in vision that involves assignment of edges to regions for purposes of shape determination

Kanizsa triangle
Kanizsa triangle

In addition, Gestalt theory can be used to explain the illusory contours in the Kanizsa Triangle. Illusory contours or subjective contours are a form of Visual illusion where contours are perceived without a Luminance or color change across the contour A floating white triangle, which does not exist, is seen. The brain has a need to see familiar simple objects and has a tendency to create a "whole" image from individual elements. [2] Gestalt means "whole" in German. However, another explanation of the Kanizsa Triangle is based in evolutionary psychology and the fact that in order to survive it was important to see form and edges. Evolutionary psychology ( EP) attempts to explain mental and psychological traits such as Memory, Perception, The use of perceptual organization to create meaning out of stimuli is the principle behind other well-known illusions including impossible objects. An impossible object (also known as an impossible figure or an undecidable figure) is a type of Optical illusion consisting of a two- Dimensional Our brain makes sense of shapes and symbols putting them together like a jigsaw puzzle, formulating that which isn't there to that which is believable.

Depth and motion perception

Illusions can be based on an individual's ability to see in three dimensions even though the image hitting the retina is only two dimensional. The Ponzo illusion is an example of an illusion which uses monocular cues of depth perception to fool the eye. The Ponzo illusion is an Optical illusion that was first demonstrated by the Italian psychologist Mario Ponzo (1882-1960 in 1913

Ponzo Illusion
Ponzo Illusion

In the Ponzo illusion the converging parallel lines tell the brain that the image higher in the visual field is further away therefore the brain perceives the image to be larger, although the two images hitting the retina are the same size. The term visual field is sometimes used as a Synonym to Field of view, though they do not designate the same thing The Optical illusion seen in a diorama/false perspective also exploits assumptions based on monocular cues of depth perception. The word diorama can refer either to a nineteenth century mobile theatre device or in modern usage a three-dimensional model usually enclosed in a glass showcase for a museum The word diorama can refer either to a nineteenth century mobile theatre device or in modern usage a three-dimensional model usually enclosed in a glass showcase for a museum Depth perception is the visual ability to perceive the world in three Dimensions Although any animal capable of moving around its environment must be able to The M. C. Escher painting Waterfall exploits rules of depth and proximity and our understand of the physical world to create an illusion. Maurits Cornelis Escher (17 June 1898 – 27 March 1972 usually referred to as M Waterfall is a lithograph print by the Dutch artist M C Escher which was first printed in October 1961.

Like depth perception, motion perception is responsible for a number of sensory illusions. Depth perception is the visual ability to perceive the world in three Dimensions Although any animal capable of moving around its environment must be able to Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs Film animation is based on the illusion that the brain perceives a series of slightly varied images produced in rapid succession as a moving picture. The bouncing ball animation (below consists of these 6 frames Likewise, when we are moving, as we would be while riding in a vehicle, stable surrounding objects may appear to move. We may also perceive a large object, like an airplane, to move more slowly, than smaller objects, like a car, although the larger object is actually moving faster. The Phi phenomenon is yet another example of how the brain perceives motion, which is most often created by blinking lights in close succession. The phi phenomenon is a perceptual Illusion described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion,

Color and brightness constancies

Simultaneous Contrast Illusion. The horizontal grey bar is the same shade throughout
Simultaneous Contrast Illusion. The horizontal grey bar is the same shade throughout
In this illusion, the second card from the left seems to be a stronger shade of pink in the top picture. In fact they are the same colour, but the brain changes its assumption about colour due to the colour cast of the surrounding photo.
In this illusion, the second card from the left seems to be a stronger shade of pink in the top picture. In fact they are the same colour, but the brain changes its assumption about colour due to the colour cast of the surrounding photo.

Perceptual constancies are sources of illusions. Color constancy and brightness constancy are responsible for the fact that a familiar object will appear the same color regardless of the amount of or colour of light reflecting from it. Color constancy is an example of Subjective constancy and a feature of the human Color perception system which ensures that the perceived color of objects remains An illusion of color or contrast difference can be created when the luminosity or colour of the area surrounding an unfamiliar object is changed. The contrast of the object will appear darker against a black field which reflects less light compared to a white field even though the object itself did not change in color. Similarly, the eye will compensate for colour contrast depending on the colour cast of the surrounding area.

Object consistencies

Like color, the brain has the ability to understand familiar objects as having a consistent shape or size. For example a door is perceived as rectangle regardless as to how the image may change on the retina as the door is opened and closed. Unfamiliar objects, however, do not always follow the rules of shape constancy and may change when the perspective is changed. The Shepard illusion of the changing table is an example of an illusion based on distortions in shape constancy.

Future perception

Researcher Mark Changizi of Rensselaer Polytechnic Institute in New York says optical illusions are due to a neural lag which most humans experience while awake. Rensselaer Polytechnic Institute, or RPI, is a Nonsectarian private Research University located in Troy, New York When light hits the retina, about one-tenth of a second goes by before the brain translates the signal into a visual perception of the world. Scientists have known of the lag, yet they have debated over how humans compensate, with some proposing that our motor system somehow modifies our movements to offset the delay.

Changizi asserts that the human visual system has evolved to compensate for neural delays, generating images of what will occur one-tenth of a second into the future. This foresight enables human to react to events in present. This allows humans to perform reflexive acts like catching a fly ball and to maneuver smoothly through a crowd. [3] Illusions occur when our brains attempt to perceive the future, and those perceptions don't match reality. For example, one illusion called the Hering illusion, looks like bike spokes around a central point, with vertical lines on either side of this central, so-called vanishing point. The Hering illusion is an Optical illusion discovered by the German physiologist Ewald Hering in 1861. The illusion tricks us into thinking we are moving forward, and thus, switches on our future-seeing abilities. Since we aren't actually moving and the figure is static, we misperceive the straight lines as curved ones.

Chnagizi said:

"Evolution has seen to it that geometric drawings like this elicit in us premonitions of the near future. The converging lines toward a vanishing point (the spokes) are cues that trick our brains into thinking we are moving forward - as we would in the real world, where the door frame (a pair of vertical lines) seems to bow out as we move through it - and we try to perceive what that world will look like in the next instant. " [3]

Illusions

An optical illusion. The two circles seem to move when the viewer's head is moving forwards and backwards while looking at the black dot.
An optical illusion. The two circles seem to move when the viewer's head is moving forwards and backwards while looking at the black dot.
Floor tiles at the Basilica of St. John Lateran in Rome. The pattern creates an illusion of three-dimensional boxes.
Floor tiles at the Basilica of St. John Lateran in Rome. The Basilica of St John Lateran ( Italian: Basilica di San Giovanni in Laterano) is the Cathedral of the church of Rome and the official Rome ( Roma ˈroma Roma is the capital city of Italy and Lazio, and is Italy's largest and most populous city with more than 2 The pattern creates an illusion of three-dimensional boxes.
The Spinning Dancer appears to move both clockwise and counter-clockwise
The Spinning Dancer appears to move both clockwise and counter-clockwise

Artists have worked with optical illusions, including M. C. Escher, Bridget Riley, Salvador Dalí, Giuseppe Arcimboldo, Marcel Duchamp, Oscar Reutersvärd, and Charles Allan Gilbert. The Spinning Dancer, also known as the silhouette illusion, is a kinetic bistable Optical illusion resembling a pirouetting female dancer An Ames room is a distorted room that is used to create an Optical illusion. The Ames trapezoid or Ames window is a style of Window which when observed frontally appears to be a rectangular window but is in fact a trapezoid An autostereogram is a single-image Stereogram (SIS designed to create the visual illusion of a three- Dimensional (3D scene from a two-dimensional The barberpole illusion is a Visual illusion that reveals biases in the processing of visual motion in the human brain Benham's top, also called Benham's disk is named after the English toymaker Charles Benham, who in 1895 sold a top painted with the pattern shown at right The Bezold effect is an Optical illusion, named after a German professor of meteorology Wilhelm von Bezold (1837-1907 who discovered that a color may appear different A blivet, also known as a poiuyt, is an undecipherable figure an Optical illusion and an Impossible object. A blivet, also known as a poiuyt, is an undecipherable figure an Optical illusion and an Impossible object. The café wall illusion is an Optical illusion, first described by Richard Gregory in 1973 Chubb illusion is an Optical illusion wherein the apparent contrast of an object varies dramatically depending on the context of the presentation The Cornsweet illusion, also known as Craik-O'Brien-Cornsweet illusion or Craik-Cornsweet illusion, is an Optical illusion that was described in detail The Ebbinghaus illusion is an Optical illusion of relative size perception The Ehrenstein illusion is an Optical illusion studied by the German psychologist Walter Ehrenstein in which the sides of a square placed inside a pattern of concentric The flash lag illusion or flash-lag effect is a Visual illusion wherein a flash and a moving object that appear in the same location are perceived to be displaced The Fraser spiral illusion is an Optical illusion that was first described by the British psychologist James Fraser in 1908 A grid illusion is any kind of Grid that deceives a person's vision The Hering illusion is an Optical illusion discovered by the German physiologist Ewald Hering in 1861. The Hollow-Face illusion is an Optical illusion in which the perception of a concave mask of a face appears as a normal convex face An isometric illusion (also called an ambiguous figure or inside/outside illusion) is a type of Optical illusion, specifically one due to Multistable The Jastrow illusion is an Optical illusion discovered by the American psychologist Joseph Jastrow in 1889. The Leaning Tower Illusion is an Optical illusion that presents two identical images of the Leaning Tower of Pisa side by side Lilac chaser is a Visual illusion, also known as the Pac-Man illusion. Mach bands are an Optical illusion consisting of an image of two wide bands one light and one dark separated by a narrow strip with a light-to-dark gradient The McCollough effect is a phenomenon of human Visual perception in which colorless Gratings appear colored depending on ( contingent on the 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. It has been suggested that this article or section be merged into Illusory motion. The Müller-Lyer illusion is an 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 Orbison illusion is an Optical illusion that was first described by the psychologist William Orbison in 1939 The Penrose triangle, also known as the tribar, is an Impossible object. The peripheral drift illusion (PDI refers to a motion illusion generated by the presentation of a sawtooth luminance grating in the visual periphery The phi phenomenon is a perceptual Illusion described by Max Wertheimer in his 1912 Experimental Studies on the Seeing of Motion, The Poggendorff Illusion is an Optical illusion that involves the brain's perception of the interaction between diagonal lines and horizontal and vertical edges The Ponzo illusion is an Optical illusion that was first demonstrated by the Italian psychologist Mario Ponzo (1882-1960 in 1913 The Pulfrich effect is a psychophysical phenomenon wherein lateral motion of an object in the field of view is interpreted by the Visual cortex as having a depth component due Rubin's vase (sometimes known as the Rubin face or the Figure-ground vase) is a famous set of cognitive The same color illusion — also known as Adelson's checker shadow illusion, checker shadow illusion and checker shadow — is an Optical illusion The Sander illusion or Sander's parallelogram is an Optical illusion described by the German psychologist Friedrich Sander (1889-1971 in 1926 Size-weight illusion is also known as Charpentier illusion (or Charpentier-Koseleff illusion The Spinning Dancer, also known as the silhouette illusion, is a kinetic bistable Optical illusion resembling a pirouetting female dancer The wagon-wheel effect (alternatively or stagecoach-wheel effect, stroboscopic effect) is an Optical illusion in which a Spoked Wheel White's illusion is an Optical illusion illustrating the fact that the same target Luminance can elicit different perceptions of Brightness in different The Wundt illusion is an Optical illusion that was first described by the German psychologist Wilhelm Wundt in the 19th century The Zöllner illusion is a classic Optical illusion named after its discoverer German astrophysicist Johann Karl Friedrich Zöllner. Maurits Cornelis Escher (17 June 1898 – 27 March 1972 usually referred to as M For the boxer see Bridgett Riley. Bridget Louise Riley CH CBE (born April 24, 1931 in Norwood Salvador Domingo Felipe Jacinto Dalí i Domènech 1st Marquis of Púbol (May 11 1904 &ndash January 23 1989 was a Spanish Catalan Surrealist Giuseppe Arcimboldo (also spelled Arcimboldi; 1527 - July 11 1593) was an Italian painter best known for creating imaginative Marcel Duchamp (maʀsɛl dyˈʃɑ̃ (28 July 1887 &ndash 2 October 1968 was a French artist whose work is most often associated with the Dadaist and Surrealist Oscar Reutersvärd (1915 Stockholm, Sweden&ndash February 2, 2002) "the father of the impossible figure" was an artist who pioneered the art Charles Allan Gilbert (1873-1929 was a US artist and illustrator Also some contemporary artists are experimenting with illusions, including: Octavio Ocampo, Dick Termes, Shigeo Fukuda, Patrick Hughes (artist), István Orosz, Rob Gonsalves and Akiyoshi Kitaoka. Octavio Ocampo was born on 28 February 1943 in Celaya, Guanajuato, Mexico. Dick Termes is an innovative American artist who uses a six point perspective system that he devised to create unique paintings on large spheres called Termespheres Shigeo Fukuda (福田 繁雄 born February 4, 1932, Tokyo) is a Sculptor, Graphic artist and Poster Designer Patrick Hughes (born 20 October 1939) is British artist working in London István Orosz (b October 24 1951 Kecskemét) Hungarian painter, printmaker Graphic designer and animated film director is known for Rob Gonsalves is a Canadian painter of Magic realism Both his parents were Romanian Gypsies who travelled from place to place in Romania Optical illusion is also used in film by the technique of forced perspective. Forced perspective is a technique that employs Optical illusion to make an object appear farther closer larger or smaller than it actually is

Cognitive processes hypothesis

The hypothesis claims that visual illusions are because the neural circuitry in our visual system evolves, by neural learning, to a system that makes very efficient interpretations of usual 3D scenes based in the emergence of simplified models in our brain that speed up the interpretation process but give rise to optical illusions in unusual situations. In this sense, the cognitive processes hypothesis can be considered a framework for an understanding of optical illusions as the signature of the empirical statistical way vision has evolved to solve the inverse problem [1].

Research indicates that 3D vision capabilities emerge and are learned jointly with the planning of movements. After a long process of learning, an internal representation of the world emerges that is well adjusted to the perceived data coming from closer objects. The representation of distant objects near the horizon is less "adequate". In fact, it is not only the Moon that seems larger when we perceive it near the horizon. In a photo of a distant scene, all distant objects are perceived as smaller than when we observe them directly using our vision.

The retinal image is the main source driving vision but what we see is a "virtual" 3D representation of the scene in front of us. We don't see a physical image of the world. We see objects; and the physical world is not itself separated into objects. We see it according to the way our brain organizes it. The names, colors, usual shapes and other information about the things we see pop up instantaneously from our neural circuitry and influence the representation of the scene. We "see" the most relevant information about the elements of the best 3D image that our neural networks can produce. The illusions arise when the "judgments" implied in the unconscious analysis of the scene are in conflict with reasoned considerations about bite.

Gallery

Illusion movie.ogg

Stare at the centre

An example movie which produces distortion illusion after watching the movie then looking away.

Tesseract

Café wall illusion

Lilac chaser

References

  1. ^ Pinel, J. Geometry The tesseract can be constructed in a number of different ways The café wall illusion is an Optical illusion, first described by Richard Gregory in 1973 Lilac chaser is a Visual illusion, also known as the Pac-Man illusion. (2005) Biopsychology (6th ed. ). Boston: Allyn & Bacon. ISBN 0-205-42651-4
  2. ^ a b Myers, D. (2003). Psychology in Modules, (7th ed. ) New York: Worth. ISBN 0-7167-5850-4
  3. ^ a b Key to All Optical Illusions Discovered, Jeanna Bryner, Senior Writer, LiveScience. com 6/2/08. His research on this topic is detailed in the May/June issue of the journal Cognitive Science.

See also

External links

Dictionary

optical illusion

-noun

  1. An image that is visually deceptive or misleading.
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