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Geometrical-optical Illusions
Geometrical-optical illusions 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. Geometrical properties In studying geometry one concentrates on the position of points and on the length, orientation and curvature of lines. Geometrical-optical illusions then relate in the first instance to object characteristics as defined by geometry. Though vision is three-dimensional, in many situations depth can be factored out and attention concentrated on a simple view of a two-dimensional tablet with its x and y co-ordinates.' Illusions are in visual space Whereas their counterparts in the observer's object space are public and have measurable properties, the illusions themselves are private to the observer's (human or animal) experience. Nevertheless, they are accessible to portrayal by verbal and other communication and even to measurement by psychophysics. A nulling techniqu ...
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Visual Illusions
Within visual perception, an optical illusion (also called a visual 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 immerged in water; an example for a physiological paradox is the motion aftereffect (where, despite movement, position remains unchanged). An example for a physiological fiction is an afterimage. Three typical cognitive distortions are the Ponzo, Poggendorff, and Müller-Lyer illusion. Physical illusions are ...
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Delboeuf Illusion
The Delboeuf illusion is an optical illusion of relative size perception: In the best-known version of the illusion, two discs of identical size have been placed near to each other and one is surrounded by a ring; the surrounded disc then appears larger than the non-surrounded disc if the ring is close, while appearing smaller than the non-surrounded disc if the ring is distant. A 2005 study suggests it is caused by the same visual processes that cause the Ebbinghaus illusion. Eponym The illusion was named for the Belgian philosopher, mathematician, experimental psychologist, hypnotist, and psychophysicist Joseph Remi Leopold Delboeuf (1831–1896), who created it in 1865. Factors According to Girgus and Coren (1982) the Delboeuf illusion uses both assimilation and contrast as elements in its perception distortion. Assimilation is the predominant factor in the disc in the smaller outer ring (the example on the right in the image above). Girgus and Coren mentioned that this i ...
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Max Wertheimer
Max Wertheimer (April 15, 1880 – October 12, 1943) was an Austro-Hungarian psychologist who was one of the three founders of Gestalt psychology, along with Kurt Koffka and Wolfgang Köhler. He is known for his book, ''Productive Thinking'', and for conceiving the phi phenomenon as part of his work in Gestalt psychology. Wertheimer became interested in psychology and studied under Carl Stumpf at the University of Berlin.Hothersall, D. (2003) Wertheimer then went on to obtain his PhD in 1904 under Oswald Külpe, at the University of Würzburg and then began his intellectual career teaching at the Institute for Social Research at Frankfurt University. For a short time, he left Frankfurt to work at the Berlin Psychological Institute, but returned in 1929 as a full professor. Wertheimer eventually joined the faculty of The New School in New York, a position he held until his death. Early life Max Wertheimer was born on April 15, 1880, in Prague, then part of the Bohemian Austria-Hunga ...
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Gestalt Psychology
Gestalt-psychology, gestaltism, or configurationism is a school of psychology that emerged in the early twentieth century in Austria and Germany as a theory of perception that was a rejection of basic principles of Wilhelm Wundt's and Edward Titchener's elementalist and structuralist psychology.Mather, George (2006) Foundations of Perception, Psychology Pressch.1 p.32 As used in Gestalt psychology, the German word ''Gestalt'' ( , ; meaning "form") is interpreted as "pattern" or "configuration". Gestalt psychologists emphasize that organisms perceive entire patterns or configurations, not merely individual components. The view is sometimes summarized using the adage, "the whole is more than the sum of its parts." Gestalt psychology was founded on works by Max Wertheimer, Wolfgang Köhler, and Kurt Koffka. Origin and history Max Wertheimer (1880–1943), Kurt Koffka (1886–1941), and Wolfgang Köhler (1887-1967) founded Gestalt psychology in the early 20th century. The domi ...
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Perspective (graphical)
Linear or point-projection perspective (from la, perspicere 'to see through') is one of two types of 3D projection, graphical projection perspective in the graphic arts; the other is parallel projection. Linear perspective is an approximate representation, generally on a flat surface, of an image as it is seen by the eye. Perspective drawing is useful for representing a three-dimensional scene in a two-dimensional medium, like paper. The most characteristic features of linear perspective are that objects appear smaller as their distance from the observer increases, and that they are subject to ''foreshortening'', meaning that an object's dimensions along the line of sight appear shorter than its dimensions across the line of sight. All objects will recede to points in the distance, usually along the horizon line, but also above and below the horizon line depending on the view used. Italian Renaissance painters and architects including Masaccio, Paolo Uccello, Piero della Fran ...
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Size Constancy
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. Visual There are several types of perceptual constancies in visual perception: * ''Size constancy'' is one type of visual subjective constancy. Within a certain range, people's perception of one particular object's size will not change, regardless of changes in distance or the video size change on the retina. The perception of image is still based upon the actual size of the perceptual characteristics. According to optical principles, for the same object, the size of the image on the retina changes as the distance from the object to the observer changes. The greater the distance, the smaller the image is sensed by the retina. When someone is observing an ob ...
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Illusory Contours
Illusory contours or subjective contours are visual illusions that evoke the perception of an edge without a luminance or color change across that edge. Illusory brightness and depth ordering often accompany illusory contours. Friedrich Schumann is often credited with the discovery of illusory contours around the beginning of the 20th century, but they are present in art dating to the Middle Ages. Gaetano Kanizsa’s 1976 ''Scientific American'' paper marked the resurgence of interest in illusory contours for vision scientists. Common types of illusory contours Kanizsa figures Perhaps the most famous example of an illusory contour is the Pac-Man configuration popularized by Gaetano Kanizsa. Kanizsa figures trigger the percept of an illusory contour by aligning Pac-Man-shaped inducers in the visual field such that the edges form a shape. Although not explicitly part of the image, Kanizsa figures evoke the percept of a shape, defined by a sharp illusory contour. Typically, the sh ...
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Roger Penrose
Sir Roger Penrose (born 8 August 1931) is an English mathematician, mathematical physicist, philosopher of science and Nobel Laureate in Physics. He is Emeritus Rouse Ball Professor of Mathematics in the University of Oxford, an emeritus fellow of Wadham College, Oxford, and an honorary fellow of St John's College, Cambridge and University College London. Penrose has contributed to the mathematical physics of general relativity and cosmology. He has received several prizes and awards, including the 1988 Wolf Prize in Physics, which he shared with Stephen Hawking for the Penrose–Hawking singularity theorems, and one half of the 2020 Nobel Prize in Physics "for the discovery that black hole formation is a robust prediction of the general theory of relativity". He is regarded as one of the greatest living physicists, mathematicians and scientists, and is particularly noted for the breadth and depth of his work in both natural and formal sciences. Early life and education Bor ...
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Necker Cube
The Necker cube is an optical illusion that was first published as a Rhomboid in 1832 by Swiss crystallographer Louis Albert Necker. It is a simple wire-frame, two dimensional drawing of a cube with no visual cues as to its orientation, so it can be interpreted to have either the lower-left or the upper-right square as its front side. Ambiguity The Necker cube is an ambiguous drawing. Each part of the picture is ambiguous by itself, yet the human visual system picks an interpretation of each part that makes the whole consistent. The Necker cube is sometimes used to test computer models of the human visual system to see whether they can arrive at consistent interpretations of the image the same way humans do. Humans do not usually see an inconsistent interpretation of the cube. A cube whose edges cross in an inconsistent way is an example of an impossible object, specifically an impossible cube (compare Penrose triangle). With the cube on the left, most people see the lower ...
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Kanizsa Triangle
Illusory contours or subjective contours are visual illusions that evoke the perception of an edge without a luminance or color change across that edge. Illusory brightness and depth ordering often accompany illusory contours. Friedrich Schumann is often credited with the discovery of illusory contours around the beginning of the 20th century, but they are present in art dating to the Middle Ages. Gaetano Kanizsa’s 1976 ''Scientific American'' paper marked the resurgence of interest in illusory contours for vision scientists. Common types of illusory contours Kanizsa figures Perhaps the most famous example of an illusory contour is the Pac-Man configuration popularized by Gaetano Kanizsa. Kanizsa figures trigger the percept of an illusory contour by aligning Pac-Man-shaped inducers in the visual field such that the edges form a shape. Although not explicitly part of the image, Kanizsa figures evoke the percept of a shape, defined by a sharp illusory contour. Typically, the shap ...
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