List of optical illusions

Last updated November 02, 2024

Name	Example	Notes
Afterimage illusion		An afterimage or ghost image is a visual illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased.
Afterimage on empty shape (also known as color dove illusion)		This type of illusions is designed to exploit graphical similarities.
Ambiguous image		These are images that can form two separate pictures. For example, the image shown forms a rabbit and a duck.
Ambigram		A calligraphic design that has multiple or symmetric interpretations.
Ames room illusion		An Ames room is a distorted room that is used to create a visual illusion.
Ames trapezoid window illusion		A window is formed in the shape of a trapezium. It is often hung and spun around to provide the illusion that the window rotates through less than 180 degrees.
Autokinetic effect		The autokinetic effect, or autokinesis, occurs when a stationary image appears to move.
Autostereogram		An autostereogram is a single-image stereogram (SIS), designed to create the visual illusion of a three-dimensional (3D) scene from a two-dimensional image in the human brain. An ASCII stereogram is an image that is formed using characters on a keyboard. Magic Eye is an autostereogram book series.
Barberpole illusion		The barber pole illusion is a visual illusion that reveals biases in the processing of visual motion in the human brain.
Benham's top		When a disk that has lines or colours on it is spun, it can form arcs of colour.
Beta movement		Movement that appears to occur when fixed pictures turn on and off.
Bezold Effect		An apparent change of tone of a colour due to the alteration of the colour of the background.
Blivet		Also known as "poiuyt" or "devil's fork", this illusion is an impossible image because in reality the shape cannot exist.
Café wall illusion		This illusion is a pattern in which the mortar or grout between different coloured bricks or tiles on a wall appear to form non-parallel, straight lines, despite the lines being parallel (and straight). Its name comes from a café wall that produced the illusion.
Catoptric cistula		A catoptric cistula is a box with insides made of mirrors so as to distort images of objects put into the box.
Checker shadow illusion		The checker shadow illusion shows that when a shadow is cast onto a checked board, the colours of squares A and B in the photos appear to be different, when in fact they are the same.
Chubb illusion		The Chubb illusion is an optical illusion or error in visual perception in which the apparent contrast of an object varies substantially to most viewers depending on its relative contrast to the field on which it is displayed.
Color constancy		Colour 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 relatively constant under varying illumination conditions. A green apple for instance looks green to us at midday, when the main illumination is white sunlight, and also at sunset, when the main illumination is red.
Color phi phenomenon		The color phi phenomenon is a perceptual illusion in which a disembodied perception of motion is produced by a succession of still images.
Contingent perceptual aftereffect
Convergence micropsia
Cornsweet illusion		An illusion where two colours can obviously be seen to be different when placed directly beside each other; however, when the two colours are separated by a thick black line, they appear to be of the same hue.
Crater illusion		A type of multistable illusion where an image of a concave object, rotated so that the light source is below, may sometimes appear convex, and vice versa. This phenomenon is due to the fact that light sources tend to shine from above the subject.
Delboeuf illusion		An optical illusion of relative size perception. The two black circles are exactly the same size; however, the one on the left seems larger.
Disappearing Model		A trompe-l'œil body painting by Joanne Gair.
The dress		An optical illusion resulting from the brain's attempt to discount coloured tinting from daylight and other sources.^[1] The dress was a viral phenomenon, which was either seen as blue and black or as white and gold. Its true colours were eventually confirmed to be blue and black.^[2]
Ebbinghaus illusion		The Ebbinghaus illusion, or Titchener circles, is an optical illusion of relative size perception. The two orange circles are exactly the same size; however, the one on the right appears larger.
Ehrenstein illusion		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 circles take an apparent curved shape.
Fata Morgana (mirage)		Visible in a narrow band right above the horizon, Fata Morgana mirages significantly distort the object or objects on which they are based, often such that the object is completely unrecognizable. A Fata Morgana may be seen on land or at sea, in polar regions, or in deserts. It may involve almost any kind of distant object, including boats, islands, and the coastline.
Fechner color
Figure-ground (perception)
Filling-in
Flash lag illusion
Forced perspective		Application used in film and architecture to create the illusion of larger, more distant objects.
Fraser spiral illusion		The Fraser spiral illusion, or false spiral, or the twisted cord illusion, was first described by the British psychologist Sir James Fraser in 1908. The overlapping black arc segments appear to form a spiral; however, the arcs are a series of concentric circles.
Gravity hill
Grid illusion		Any kind of grid that deceives a person's vision. The two most common types of grid illusions are the Hermann grid illusion (1870) and the scintillating grid illusion (1994). The first is characterized by "ghostlike" grey blobs perceived at the intersections of a white (or light-colored) grid on a black background. The grey blobs disappear when looking directly at an intersection. The second is constructed by superimposing white discs on the intersections of orthogonal gray bars on a black background. Dark dots seem to appear and disappear rapidly at random intersections, hence the label "scintillating". When a person keeps their eyes directly on a single intersection, the dark dot does not appear. The dark dots disappear if one is too close to or too far from the image.
Hering illusion		The Hering illusion (1861): When two straight and parallel lines are presented in front of radial background (like the spokes of a bicycle), the lines appear as if they were bowed outwards.
Hollow-Face illusion		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.
Hybrid image		A Hybrid image is an optical illusion developed at MIT in which an image can be interpreted in one of two different ways depending on viewing distance.
Illusory contours		Illusory contours or subjective contours are a form of visual illusion where contours are perceived without a luminance or color change across the contour.
Impossible object
Irradiation illusion
Isometric illusion		An isometric illusion (also called an ambiguous figure or inside/outside illusion) is a type of optical illusion, specifically one due to multistable perception.
Jastrow illusion		The Jastrow illusion is an optical illusion discovered by the American psychologist Joseph Jastrow in 1889.
Kanizsa triangle		The Kanizsa triangle is an optical illusion first described by the Italian psychologist Gaetano Kanizsa in 1955. It is a triangle formed of illusory contours.
Kinetic Depth Effect		The Kinetic depth effect refers to the phenomenon whereby the three-dimensional structural form of a silhouette can be perceived when the object is moving. In the absence of other visual depth cues, this might be the only perception mechanism available to infer the object's shape. Additionally the direction of motion can reverse due to the existence of multiple 3D visual solutions.
Leaning tower illusion		The Leaning tower illusion is an optical illusion that presents two identical images of the Leaning Tower of Pisa side by side.
Lilac chaser		Lilac chaser is a visual illusion, also known as the Pac-Man illusion.
Liquid crystal shutter glasses
Lunar terminator illusion		Lunar terminator illusion is an optical illusion where the apparent source of sunlight illuminating the moon does not corresponding with the actual position of the sun.
Mach bands		Mach bands is an optical illusion named after the physicist Ernst Mach.
McCollough effect		The McCollough effect (1965) is a phenomenon of human visual perception in which colorless gratings appear colored contingent on the orientation of the gratings. It is an aftereffect requiring a period of induction to produce it.
Missing square puzzle		The missing square puzzle is an optical illusion used in mathematics classes to help students reason about geometrical figures.
Moon illusion		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.
Motion aftereffect
Motion illusion
Müller-Lyer illusion		The Müller-Lyer illusion is an optical illusion consisting of a stylized arrow.
Multistable perception
Necker cube		The Necker cube is an optical illusion first published in 1832 by Swiss crystallographer Louis Albert Necker.
Numerosity adaptation effect
Orbison illusion		The Orbison illusion is an optical illusion that was first described by the psychologist William Orbison in 1939.
Oppel-Kundt illusion		The Oppel-Kundt illusion is an optical illusion 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).
Penrose stairs		The Penrose stairs was created by Lionel Penrose and his son Roger Penrose.^[3] A variation on the Penrose triangle, it is a two-dimensional depiction of a staircase in which the stairs make four 90-degree turns as they ascend or descend yet form a continuous loop, so that a person could climb them forever and never get any higher.
Penrose triangle		The Penrose triangle was first created by the Swedish artist Oscar Reutersvärd in 1934. The mathematician Roger Penrose independently devised and popularised it in the 1950s, describing it as "impossibility in its purest form".
Pepper's ghost
Perceived visual angle
Peripheral drift illusion		A motion illusion (1979/1999) generated by the presentation of a sawtooth luminance grating in the visual periphery.
Phantogram		Phantograms, also known as Phantaglyphs, Op-Ups, free-standing anaglyphs, levitated images, and book anaglyphs, are a form of optical illusion.
Phi phenomenon
Poggendorff illusion		The Poggendorff illusion (1860) involves the misperception of the position of one segment of a transverse line that has been interrupted by the contour of an intervening structure (here a rectangle).
Ponzo illusion		In the Ponzo illusion (1911) two identical lines across a pair of converging lines, similar to railway tracks, are drawn. The upper line looks longer because we interpret the converging sides according to linear perspective as parallel lines receding into the distance. In this context, we interpret the upper line as though it were farther away, so we see it as longer – a farther object would have to be longer than a nearer one for both to produce retinal images of the same size.
Pulfrich effect		The Pulfrich effect is the effect that covering one eye with transparent but darkened glass can cause purely lateral motion to appear to have a depth component even though in reality it doesn't; even a completely flat scene such as one shown on a television screen can appear to exhibit some three-dimensional motion, but this is an illusion due to the fact that darkening the scene for one eye causes the photoreceptors in that eye to respond more slowly.
Rubin vase		Rubin vase (1915): an ambiguous or bi-stable (i.e., reversing) two-dimensional form.
Sander illusion		In Sander's parallelogram (1926) the diagonal line bisecting the larger, left-hand parallelogram appears to be considerably longer than the diagonal line bisecting the smaller, right-hand parallelogram, but is in fact the same length.
Silencing		Silencing is an illusion in which a set of objects that change in luminance, hue, size, or shape appears to stop changing when it moves.
Size–weight illusion		The size–weight illusion is also known as the Charpentier illusion or Charpentier–Koseleff illusion.
Stepping feet illusion		The stepping feet illusion is influenced by the contrast between moving objects and their background.
Stroboscopic effect
Swept-plane display
Ternus illusion		The Ternus illusion (1926/1938) is based upon apparent motion.
Thaumatrope		A thaumatrope is a toy that was popular in Victorian times.
Trompe-l'œil
Troxler's fading		Troxler's fading: When one fixates on a particular point for even a short period of time, an unchanging stimulus away from the fixation point will fade away and disappear.
Vanishing puzzle		A vanishing puzzle is a mechanical optical illusion showing different numbers of a certain object when parts of the puzzle are moved around.^[4]
Vertical–horizontal illusion		The Vertical-horizontal illusion is the tendency for observers to overestimate the length of a vertical line relative to a horizontal line of the same length.
Vista paradox
Visual tilt effects
Wagon-wheel effect
White's illusion
Wundt illusion		The two red vertical lines are both straight, but they may look as if they are bowed inwards to some observers. The distortion is induced by the crooked lines on the background
Zoetrope
Zöllner illusion		The Zöllner illusion is a classic optical illusion named after its discoverer, German astrophysicist Johann Karl Friedrich Zöllner.

Notes

↑ "The Science of Why No One Agrees on the Colour of This Dress". Wired. 2015-02-27. Archived from the original on 28 February 2015. Retrieved 27 February 2015.
↑ "Optical illusion: Dress color debate goes global". BBC News. BBC. Archived from the original on 2019-07-13. Retrieved 28 February 2015.
↑ Penrose, LS; Penrose, R. (1958). "Impossible objects: A special type of optical illusion". British Journal of Psychology. 49 (1): 31–33. doi:10.1111/j.2044-8295.1958.tb00634.x. PMID 13536303.
↑ The Guardian, Vanishing Leprechaun, Disappearing Dwarf and Swinging Sixties Pin-up Girls – puzzles in pictures

External links

Optical Illusion Examples by Great Optical Illusions
Optical Illusions & Visual Phenomena by Michael Bach
Optical Illusions Database by Mighty Optical Illusions
Optical illusions and perception paradoxes by Archimedes Lab
https://web.archive.org/web/20100419004856/http://ilusaodeotica.com/ hundreds of optical illusions
Project LITE Atlas of Visual Phenomena Archived 2010-03-29 at the Wayback Machine
Akiyoshi's illusion pages Professor Akiyoshi KITAOKA's anomalous motion illusions
Spiral Or Not? by Enrique Zeleny, Wolfram Demonstrations Project
Magical Optical Illusions by Rangki
Hunch Optical Illusions by Hunch
Optical Illusions by Ooh, My Brain!

Related Research Articles

An illusion is a distortion of the senses, which can reveal how the mind normally organizes and interprets sensory stimulation. Although illusions distort the human perception of reality, they are generally shared by most people.

In visual perception, an optical illusion 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 but a classification 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. A classical example for a physical distortion would be the apparent bending of a stick half immersed in water; an example for a physiological paradox is the motion aftereffect. An example for a physiological fiction is an afterimage. Three typical cognitive distortions are the Ponzo, Poggendorff, and Müller-Lyer illusion. Physical illusions are caused by the physical environment, e.g. by the optical properties of water. Physiological illusions arise in the eye or the visual pathway, e.g. from the effects of excessive stimulation of a specific receptor type. Cognitive visual illusions are the result of unconscious inferences and are perhaps those most widely known.

<span class="mw-page-title-main">Penrose triangle</span> Impossible object

The Penrose triangle, also known as the Penrose tribar, the impossible tribar, or the impossible triangle, is a triangular impossible object, an optical illusion consisting of an object which can be depicted in a perspective drawing. It cannot exist as a solid object in ordinary three-dimensional Euclidean space, although its surface can be embedded isometrically in five-dimensional Euclidean space. It was first created by the Swedish artist Oscar Reutersvärd in 1934. Independently from Reutersvärd, the triangle was devised and popularized in the 1950s by psychiatrist Lionel Penrose and his son, the mathematician and Nobel Prize laureate Roger Penrose, who described it as "impossibility in its purest form". It is featured prominently in the works of artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it.

An impossible object is a type of optical illusion that consists of a two-dimensional figure which is instantly and naturally understood as representing a projection of a three-dimensional object but cannot exist as a solid object. Impossible objects are of interest to psychologists, mathematicians and artists without falling entirely into any one discipline.

Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions

The Cornsweet illusion, also known as the Craik–O'Brien–Cornsweet illusion or the Craik–Cornsweet illusion, is an optical illusion that was described in detail by Tom Cornsweet in the late 1960s. Kenneth Craik and Vivian O'Brien had made earlier observations in a similar vein.

The Penrose stairs or Penrose steps, also dubbed the impossible staircase, is an impossible object created by Oscar Reutersvärd in 1937 and later independently discovered and made popular by Lionel Penrose and his son Roger Penrose. A variation on the Penrose triangle, it is a two-dimensional depiction of a staircase in which the stairs make four 90-degree turns as they ascend or descend yet form a continuous loop, so that a person could climb them forever and never get any higher. This is clearly impossible in three-dimensional Euclidean geometry but possible in some non-Euclidean geometry like in nil geometry.

Multistable perception is a perceptual phenomenon in which an observer experiences an unpredictable sequence of spontaneous subjective changes. While usually associated with visual perception, multistable perception can also be experienced with auditory and olfactory percepts.

The Ehrenstein illusion is an optical illusion of brightness or color perception. The visual phenomena was studied by the German psychologist Walter H. Ehrenstein (1899–1961) who originally wanted to modify the theory behind the Hermann grid illusion. In the discovery of the optical illusion, Ehrenstein found that grating patterns of straight lines that stop at a certain point appear to have a brighter centre, compared to the background.

<span class="mw-page-title-main">Richard Gregory</span> British psychologist (1923–2010)

Richard Langton Gregory, was a British psychologist and Professor of Neuropsychology at the University of Bristol.

Subjective constancy or perceptual constancy is the perception of an object or quality as constant even though our sensation of the object changes. While the physical characteristics of an object may not change, in an attempt to deal with the external world, the human perceptual system has mechanisms that adjust to the stimulus.

Roger Newland Shepard was an American cognitive scientist and author of the "universal law of generalization" (1987). He was considered a father of research on spatial relations. He studied mental rotation, and was an inventor of non-metric multidimensional scaling, a method for representing certain kinds of statistical data in a graphical form that can be comprehended by humans. The optical illusion called Shepard tables and the auditory illusion called Shepard tones are named for him.

<span class="mw-page-title-main">Peripheral drift illusion</span> Type of optical illusion

The peripheral drift illusion (PDI) refers to a motion illusion generated by the presentation of a sawtooth luminance grating in the visual periphery. This illusion was first described by Faubert and Herbert (1999), although a similar effect called the "escalator illusion" was reported by Fraser and Wilcox (1979). A variant of the PDI was created by Kitaoka Akiyoshi and Ashida (2003) who took the continuous sawtooth luminance change, and reversed the intermediate greys. Kitaoka has created numerous variants of the PDI, and one called "rotating snakes" has become very popular. The latter demonstration has kindled great interest in the PDI.

<i>Ascending and Descending</i> 1960 lithograph by M. C. Escher

Ascending and Descending is a lithograph print by the Dutch artist M. C. Escher first printed in March 1960. The original print measures 14 in × 11+1⁄4 in. The lithograph depicts a large building roofed by a never-ending staircase. Two lines of identically dressed men appear on the staircase, one line ascending while the other descends. Two figures sit apart from the people on the endless staircase: one in a secluded courtyard, the other on a lower set of stairs. While most two-dimensional artists use relative proportions to create an illusion of depth, Escher here and elsewhere uses conflicting proportions to create the visual paradox.

<span class="mw-page-title-main">Kinetic depth effect</span> Phenomenon of visual perception

In visual perception, the kinetic depth effect refers to the phenomenon whereby the three-dimensional structural form of an object can be perceived when the object is moving. In the absence of other visual depth cues, this might be the only perception mechanism available to infer the object's shape. Being able to identify a structure from a motion stimulus through the human visual system was shown by Hans Wallach and O'Connell in the 1950s through their experiments.

Akiyoshi Kitaoka is a Professor of Psychology at the College of Letters, Ritsumeikan University, Kyoto, Japan, who has been referred to as "a master of optical art".

Geometrical–optical are visual illusions, also optical illusions, in which the geometrical properties of what is seen differ from those of the corresponding objects in the visual field.

<span class="mw-page-title-main">The dress</span> Viral phenomenon regarding the colour of a dress

The dress was a 2015 online viral phenomenon centred on a photograph of a dress. Viewers disagreed on whether the dress was blue and black, or white and gold. The phenomenon revealed differences in human colour perception and became the subject of scientific investigations into neuroscience and vision science.

Shepard tables are an optical illusion first published in 1990 as "Turning the Tables," by Stanford psychologist Roger N. Shepard in his book Mind Sights, a collection of illusions that he had created. It is one of the most powerful optical illusions, typically creating length miscalculations of 20–25%.

Anya Christine Hurlbert, also known as Viscountess Ridley, is a British academic who is Professor of Visual Neuroscience and Dean of Advancement at Newcastle University. Her research involves the study of the interaction between colour and light, and how these are interpreted by the human brain.

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[1] "The Science of Why No One Agrees on the Colour of This Dress". Wired. 2015-02-27. Archived from the original on 28 February 2015. Retrieved 27 February 2015.

[2] "Optical illusion: Dress color debate goes global". BBC News. BBC. Archived from the original on 2019-07-13. Retrieved 28 February 2015.

[p1958-3] Penrose, LS; Penrose, R. (1958). "Impossible objects: A special type of optical illusion". British Journal of Psychology. 49 (1): 31–33. doi:10.1111/j.2044-8295.1958.tb00634.x. PMID 13536303.

[4] The Guardian, Vanishing Leprechaun, Disappearing Dwarf and Swinging Sixties Pin-up Girls – puzzles in pictures

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v t e Optical illusions (list)
Illusions	Afterimage Ambigram Ambiguous image Ames room Autostereogram Barberpole Bezold Café wall Checker shadow Chubb Cornsweet Delboeuf Ebbinghaus Ehrenstein Flash lag Fraser spiral Gravity hill Grid Hering Impossible trident Irradiation Jastrow Lilac chaser Mach bands McCollough Müller-Lyer Necker cube Oppel-Kundt Orbison Penrose stairs Penrose triangle Peripheral drift Poggendorff Ponzo Rubin vase Sander Schroeder stairs Shepard tables Spinning dancer Ternus Vertical–horizontal White's Wundt Zöllner
Popular culture	Op art Trompe-l'œil Spectropia (1864 book) Ascending and Descending (1960 drawing) Waterfall (1961 drawing) The dress (2015 photograph)
Related	Accidental viewpoint Auditory illusions Illusions Tactile illusions Temporal illusion

List of optical illusions

Contents

See also

Notes

External links

Related Research Articles