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Encyclopedia > Illusion

An illusion is a distortion of a sensory perception, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people.[1] Illusions may occur with more of the human senses than vision, but visual illusions, optical illusions, are the most well known and understood. The emphasis on visual illusions occurs because vision often dominates the other senses. For example, individuals watching a ventriloquist will perceive the voice is coming from the dummy since they are able to see the dummy mouth the words.[2] Some illusions are based on general assumptions the brain makes during perception. These assumptions are made using organizational principles, like Gestalt, an individual's ability of depth perception and motion perception, and perceptual constancy. Other illusions occur because of biological sensory structures within the human body or conditions outside of the body within one’s physical environment. Look up illusion in Wiktionary, the free dictionary. ... In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ... For other uses, see Brain (disambiguation). ... Senses are the physiological methods of perception. ... An optical illusion. ... This does not cite any references or sources. ... Ventriloquism is an act of deception in which a person (ventriloquist) manipulates his or her voice so that it appears that the voice is coming from elsewhere. ... In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ... Look up gestalt in Wiktionary, the free dictionary. ... Depth perception is the visual ability to perceive the world in three dimensions. ... Subjective constancy or perceptual constancy is the perception of an object or quality as constant under changing conditions. ... List of bones of the human skeleton Human anatomy is primarily the scientific study of the morphology of the adult human body. ...


In psychiatry and philosophy the term illusion refers to a specific form of sensory distortion. Unlike a hallucination, which is a sensory experience in the absence of a stimulus, an illusion describes a misinterpretation of a true sensation so it is perceived in a distorted manner. For example, hearing voices regardless of the environment would be a hallucination, whereas hearing voices in the sound of running water (or other auditory source) would be an illusion. Psychiatry is a branch of medicine dealing with the prevention, assessment, diagnosis, treatment, and rehabilitation of the mind and mental illness. ... The philosopher Socrates about to take poison hemlock as ordered by the court. ... A hallucination is a sensory perception experienced in the absence of an external stimulus, as distinct from an illusion, which is a misperception of an external stimulus. ...


Mimes are known for a repertoire of illusions that are created by physical means. The mime artist creates an illusion of acting upon or being acted upon an unseen object. These illusions exploit the audience's assumptions about the physical world. Well known examples include "walls", "climbing stairs", "leaning", "descending ladders", "pulling and pushing" etc. Look up mime in Wiktionary, the free dictionary. ...

Contents

Optical illusion

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
Main article: Optical illusion

An optical illusion is always characterized by visually perceived images that, at least in common sense terms, are deceptive or misleading. Therefore, the information gathered by the eye is processed by the brain to give, on the face of it, a percept that does not tally with a physical measurement of the stimulus source. A conventional assumption is that there are physiological illusions that occur naturally and cognitive illusions that can be demonstrated by specific visual tricks that say something more basic about how human perceptual systems work. Image File history File links Size of this preview: 772 × 599 pixelsFull resolution (1087 × 844 pixel, file size: 214 KB, MIME type: image/png) Prepared for Wikipedia by Adrian Pingstone in January 2004, based on the original created by Edward H. Adelson. ... Image File history File links Size of this preview: 772 × 599 pixelsFull resolution (1087 × 844 pixel, file size: 214 KB, MIME type: image/png) Prepared for Wikipedia by Adrian Pingstone in January 2004, based on the original created by Edward H. Adelson. ... Squares A and B are the same color. ... An optical illusion. ... An optical illusion. ... This does not cite any references or sources. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


Auditory illusion

Main article: Auditory illusion

An auditory illusion is an illusion of hearing, the sound equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or "impossible" sounds. In short, audio illusions highlight areas where the human ear and brain, as organic, makeshift tools, differ from perfect audio receptors (for better or for worse). One of exampes of auditory illusions is a Shepard tone. 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. ... 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. ... Hearing is one of the traditional five senses, and refers to the ability to detect sound. ... Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... Figure 1: Shepard tones forming a Shepard scale, illustrated in a sequencer A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. ...


Touch illusion

Main article: Touch illusion

Examples of touch illusions include phantom limb, the thermal grill illusion, and the tactile illusion which occurs when the middle finger is crossed over the pointer finger and the fingers are ran along the bridge of the nose to the tip with one finger on each side of the nose . In this illusion two “noses” are felt at the tip. Interestingly, with touch illusions similar brain sights are activated during illusory stimulation as actual stimulation[3]. Touch illusions can also be elicited through haptic technology[4]. These "illusory" tactile objects can be used to create "virtual objects"[5] Touch illusions are illusions that exploit the sense of touch. ... Touch illusions are illusions that exploit the sense of touch. ... This article is about the syndrome. ... The thermal grill illusion is a sensory illusion originally demonstrated in 1896 by T. Thunberg. ... The Index finger The index finger, pointer finger or forefinger is the second digit of a human hand, located between the thumb and the middle finger. ... Touch illusions are illusions that exploit the sense of touch. ...


Other senses

Illusions can occur with the other senses including that of taste and smell. It was discovered that even if some portion of the taste receptor on the tongue became damaged that illusory taste could be produced by tactile stimulation.[6]. Evidence of olfactory (smell) illusions occurred when positive or negative verbal labels were given prior to olfactory stimulation[7]. Olfaction, the sense of smell, is the detection of chemicals dissolved in air (or, by animals that breathe water, in water). ...


Disorders

Some illusions occur as result of an illness or a disorder. While these types of illusions are not shared with everyone they are typical of each condition. For example migraine suffers often report Fortification illusions. Scintillating scotoma is the most common visual aura preceding migraine and was first described by 19th century physician Hubert Airy (1838–1903). ...


References

  1. ^ Solso, R. L. (2001). Cognitive psychology (6th ed.). Boston: Allyn and Bacon.ISBN 0-205-30937-2
  2. ^ McGurk,H. & MacDonald, J.(1976). "Hearing lips and seeing voices", Nature 264, 746-748.
  3. ^ Gross, L 2006
  4. ^ Robles-De-La-Torre & Hayward 2001
  5. ^ The Cutting Edge of Haptics (MIT Technology Review article)
  6. ^ Todrank, J & Bartoshuk, L.M., 1991
  7. ^ Herz R. S. & Von Clef J., 2001

Cognitive Psychology is the school of psychology that examines internal mental processes such as problem solving, memory, and language. ... Technology Review is an innovation and technology magazine affiliated with the Massachusetts Institute of Technology. ...

See also

This article or section is in need of attention from an expert on the subject. ... A delusion is commonly defined as a fixed false belief and is used in everyday language to describe a belief that is either false, fanciful or derived from deception. ...

External links

  • What is an Illusion? by J.R. Block.
  • Optical illusions and visual phenomena by Michael Bach
  • Auditory illusions
  • Haptic Perception of Shape - touch illusions, forces and the geometry of objects, by Gabriel Robles-De-La-Torre.
  • Illusions of taste

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