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Illusion

For other uses, see illusion (disambiguation).
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.

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.

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.

Optical illusions

Enlarge picture
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.

Auditory illusions

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.

Tactile illusions

Main article: Touch illusion
Examples of tactile illusions include phantom limb, the thermal grill illusion, the cutaneous rabbit illusion and a curious illusion that occurs when the crossed index and middle fingers are run along the bridge of the nose with one finger on each side, resulting in the perception of two separate noses. Interestingly, the brain areas activated during illusory tactile perception are similar to those activated during actual tactile stimulation[3]. Tactile illusions can also be elicited through haptic technology[4]. These "illusory" tactile objects can be used to create "virtual objects"[5]

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].

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.

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

See also

External links

An illusion is an error in perception such as an optical illusion or auditory illusion.

Illusion or Illusions may also refer to:
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perception is the process of acquiring, interpreting, selecting, and organizing sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was proclaimed that building perceiving machines would take about a decade, but, needless to say,
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In animals, the brain or encephalon (Greek for "in the skull"), is the control center of the central nervous system, responsible for behavior. The brain is located in the head, protected by the skull and close to the primary sensory apparatus of vision, hearing,
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Senses are the physiological methods of perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology (or cognitive science), and philosophy of perception.
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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
..... Click the link for more information.
In psychology, visual perception is the ability to interpret visible light information reaching the eyes which is then made available for planning and action. The resulting perception is also known as eyesight, sight or vision.
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For the Batman villain, see .


Ventriloquism is an act of stagecraft in which a person (a ventriloquist) manipulates his or her voice so that it appears that the voice is coming from elsewhere.
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perception is the process of acquiring, interpreting, selecting, and organizing sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was proclaimed that building perceiving machines would take about a decade, but, needless to say,
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Gestalt is a German word that can be translated into English in various ways:
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Depth perception is the visual ability to perceive the world in three dimensions. It is a trait common to many higher animals. Depth perception allows the beholder to accurately gauge the distance to an object.
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Subjective constancy or perceptual constancy is the perception of an object or quality as constant under changing conditions.

Vision

In vision this means perceiving a color as "constant under changing conditions of illumination" (Erickson 1975, p.
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Human anatomy is primarily the scientific study of the morphology of the adult human body.[1] It is subdivided into gross anatomy and microscopic anatomy.[1]
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Psychiatry is a branch of medicine which exists to study, prevent, and treat mental disorders in humans.[1][2][3] The art and science of the clinical application of psychiatry has been considered a bridge between the social world and those who are
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Philosophy is the discipline concerned with questions of how one should live (ethics); what sorts of things exist and what are their essential natures (metaphysics); what counts as genuine knowledge (epistemology); and what are the correct principles of reasoning (logic).
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A hallucination is a perception in the absence of a stimulus that is believed to be genuine, ie. the subject experiences an imaginary stimulus as being real. A pseudohallucination is similar to an hallucination in all respects except that of absolute belief in the authenticity of
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A mime artist is someone who uses mime as a theatrical medium or as a performance art.

Mimes in film

Silent film comedians like Charles Chaplin, Harold Lloyd and Buster Keaton learned the craft of mime in the theatre but through film had a profound influence on
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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
..... Click the link for more information.
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
..... Click the link for more information.
In psychology, visual perception is the ability to interpret visible light information reaching the eyes which is then made available for planning and action. The resulting perception is also known as eyesight, sight or vision.
..... Click the link for more information.
The introduction to this article provides insufficient context for those unfamiliar with the subject matter.
Please help [ improve the introduction] to meet Wikipedia's layout standards.

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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.
..... Click the link for more information.
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.
..... Click the link for more information.
Hearing (or audition) is one of the traditional five senses, and refers to the ability to detect sound. In humans and other vertebrates, hearing is performed primarily by the auditory system: sound is detected by the ear and transduced into nerve impulses that are perceived
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Sound is a disturbance of mechanical energy that propagates through matter as a wave (through fluids as a compression wave, and through solids as both compression and shear waves).
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Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the base pitch of the tone moving upwards or downwards, it is referred to as the Shepard scale.
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Touch illusions are illusions that exploit the sense of touch. Some touch illusions require active touch (e.g., movement of the fingers or hands), whereas others can be evoked passively (e.g., with external stimuli that press against the skin).
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MeSH D010591

A phantom limb is the sensation that an amputated or missing limb is still attached to the body and is moving appropriately with other body parts (; ; ).
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The thermal grill illusion is a sensory illusion originally demonstrated in 1896 by T. Thunberg.[1] The illusion is created by an interlaced grill of warm (e.g., 40°C) and cool (20°C) bars.
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The cutaneous rabbit illusion (also known as cutaneous saltation) is a tactile illusion evoked by tapping two separate regions of the skin. Many rabbit experiments have been carried out on the forearm.
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Olfaction (also known as olfactics) refers to the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertbrates, and, by analogy, sensory cells of the antennae of invertebrates.
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