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:''For the journal of the same name, see [[Perception (journal)]]''
 
:''For the journal of the same name, see [[Perception (journal)]]''
   
In [[psychology]] and the [[cognitive science]]s, '''perception''' is the process of acquiring, interpreting, selecting, and organizing [[sense|sensory]] [[information]]. The word ''perception'' comes from the Latin ''perception-, percepio, '', meaning "receiving, collecting, action of taking possession, apprehension with the mind or senses." --OED.com. Methods of studying perception range from essentially [[biology|biological]] or [[physiology|physiological]] approaches, through [[psychological]] approaches through the [[philosophy of mind]] and in [[empiricist]] [[epistemology]], such as that of [[David Hume]], [[John Locke]], [[George Berkeley]], or as in [[Merleau Ponty]]'s affirmation of perception as the basis of all science and knowledge.
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'''Perception''' (from the Latin ''perceptio, percipio'') is the organization, identification, and interpretation of [[Sensory system|sensory]] [[information]] in order to represent and understand the environment.<ref>{{cite book |last=Schacter|first=Daniel|title=Psychology|year=2011|publisher=Worth Publishers}}</ref> All perception involves signals in the [[nervous system]], which in turn result from physical stimulation of the sense organs.<ref name="Goldstein5">Goldstein (2009) pp. 5–7</ref> For example, vision involves [[photon|light]] striking the [[retina]]s of the eyes, smell is mediated by odor [[molecules]] and hearing involves [[sound wave|pressure waves]]. Perception is not the passive receipt of these signals, but can be shaped by [[Perceptual learning|learning]], [[memory]], and [[expectation (epistemic)|expectation]].<ref name="mind_perception"/><ref name="Bernstein2010"/> Perception involves these "top-down" effects as well as the "bottom-up" process of processing sensory input.<ref name="Bernstein2010">{{cite book |last=Bernstein|first=Douglas A.|title=Essentials of Psychology|url=http://books.google.com/books?id=rd77N0KsLVkC&pg=PA123|accessdate=25 March 2011|date=5 March 2010|publisher=Cengage Learning|isbn=978-0-495-90693-3|pages=123–124}}</ref> The "bottom-up" processing is basically low-level information that's used to build up higher-level information (e.g., shapes for object recognition). The "top-down" processing refers to a person's concept and expectations (knowledge) that influence perception. Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness.<ref name="Goldstein5"/>
   
== History of the study of perception ==
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Since the rise of [[experimental psychology]] in the late 19th Century, [[perceptual psychology|psychology's understanding of perception]] has progressed by combining a variety of techniques.<ref name="mind_perception">Gregory, Richard. "Perception" in Gregory, Zangwill (1987) pp. 598–601</ref> [[Psychophysics]] measures the effect on perception of varying the physical qualities of the input. [[Sensory neuroscience]] studies the brain mechanisms underlying perception. Perceptual systems can also be studied [[computation]]ally, in terms of the information they process. [[Philosophy of perception|Perceptual issues in philosophy]] include the extent to which sensory qualities such as sounds, smells or colors exist in objective reality rather than the mind of the perceiver.<ref name="mind_perception"/>
Perception is one of the oldest fields within scientific psychology, and there are correspondingly many theories about its underlying processes. The oldest quantitative law in psychology is the [[Weber-Fechner law]], which quantifies the relationship between the intensity of physical stimuli and their perceptual effects. It was the study of perception that gave rise to the [[Gestalt psychology|Gestalt]] school of psychology, with its emphasis on [[holism|holistic]] approach.
 
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{{Main
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Although the senses were traditionally viewed as passive receptors, the study of [[illusion]]s and [[ambiguous image]]s has demonstrated that the brain's perceptual systems actively and pre-consciously attempt to make sense of their input.<ref name="mind_perception"/> There is still active debate about the extent to which perception is an active process of [[hypothesis]] testing, analogous to [[science]], or whether realistic sensory information is rich enough to make this process unnecessary.<ref name="mind_perception"/>
|1 = Historical and philosophical approaches to perception
 
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== Perception and reality ==
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The [[perceptual system]]s of the [[brain]] enable individuals to see the world around them as stable, even though the sensory information may be incomplete and rapidly varying. Human and animal brains are structured in a [[cognitive module|modular way]], with different areas processing different kinds of sensory information. Some of these modules take the form of [[Sensory Maps|sensory maps]], mapping some aspect of the world across part of the brain's surface. These different modules are interconnected and influence each other. For instance, the taste is strongly influenced by its odor.<ref name="DeVereCalvert2010_33"/>
   
[[Image:Multistability.jpg|right|thumb|260px|Ambiguous images]]Many [[cognitive psychology|cognitive psychologists]] hold that, as we move about in the world, we create a [[model (abstract)|model]] of how the world works. That is, we sense the objective world, but our sensations map to [[percept]]s, and these percepts are provisional, in the same sense that scientific hypotheses are provisional (cf. in the [[scientific method]]).
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==Process and terminology <!-- linked from disambiguation: update or define {{Anchor|Process and terminology}} if changed -->==
As we acquire new [[information]], our percepts shift. [[Abraham Pais]]' biography refers to the 'esemplastic' nature of [[imagination]]. In the case of visual perception, some people can actually see the percept shift in their [[mind's eye]]. Others who are not [[picture thinking|picture thinkers]], may not necessarily perceive the 'shape-shifting' as their world changes. The 'esemplastic' nature has been shown by experiment: an [[ambiguous image]] has multiple interpretations on the perceptual level.
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The process of perception begins with an object in the real world, termed the ''distal stimulus'' or ''distal object''.<ref name="Goldstein5"/> By means of light, sound or another physical process, the object stimulates the body's sensory organs. These sensory organs transform the input energy into neural activity—a process called ''transduction''.<ref name="Goldstein5"/><ref name="pomerantz"/> This raw pattern of neural activity is called the ''proximal stimulus''.<ref name="Goldstein5"/> These neural signals are transmitted to the brain and processed.<ref name="Goldstein5"/> The resulting mental re-creation of the distal stimulus is the ''percept''. Perception is sometimes described as the process of constructing [[mental representation]]s of distal stimuli using the information available in proximal stimuli.
   
Just as one object can give rise to multiple percepts, so an object may fail to give rise to any percept at all: if the percept has no grounding in a person's experience, the person may literally not perceive it.
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An example would be a person looking at a shoe. The shoe itself is the distal stimulus. When light from the shoe enters a person's eye and stimulates their retina, that stimulation is the proximal stimulus.<ref>{{cite web|url= http://www.learner.org/discoveringpsychology/07/e07glossary.html|title= Sensation and Perception}}</ref> The image of the shoe reconstructed by the brain of the person is the percept. Another example would be a telephone ringing. The ringing of the telephone is the distal stimulus. The sound stimulating a person's auditory receptors is the proximal stimulus, and the brain's interpretation of this as the ringing of a telephone is the percept. The different kinds of sensation such as warmth, sound, and taste are called "[[stimulus modality|sensory modalities]]".<ref name="pomerantz">Pomerantz, James R. (2003): "Perception: Overview". In: Lynn Nadel (Ed.), ''Encyclopedia of Cognitive Science'', Vol. 3, London: Nature Publishing Group, pp. 527–537</ref><ref name="WillisCoggeshall2004">{{cite book |last1=Willis|first1=William D.|last2=Coggeshall|first2=Richard E.|title=Sensory Mechanisms of the Spinal Cord: Primary afferent neurons and the spinal dorsal horn|url=http://books.google.com/books?id=uqnKCewO2voC&pg=PA1|accessdate=25 March 2011|date=31 January 2004|publisher=Springer|isbn=978-0-306-48033-1|page=1}}</ref>
   
This confusing [[ambiguity]] of perception is exploited in human technologies such as [[camouflage]], and also in biological [[mimicry]], for example by [[Peacock (butterfly)|Peacock butterflies]], whose wings bear eye markings that birds respond to as though they were the eyes of a dangerous [[predator]]. Perceptual ambiguity is not restricted to vision. For example, recent [[Somatosensory system|touch perception]] research ([http://www.roblesdelatorre.com/gabriel/GR-VH-Nature2001.pdf Robles-De-La-Torre & Hayward 2001]) found that [[kinesthesia]]-based [[haptic]] perception strongly relies on the forces experienced during touch. This makes it possible to produce [http://www.roblesdelatorre.com/gabriel/haptics.htm illusory touch percepts] (see also the MIT Technology Review article [http://www.technologyreview.com/read_article.aspx?id=17363&ch=biotech&sc=&pg=1 The Cutting Edge of Haptics]).
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Psychologist Jerome Bruner has developed a model of perception. According to him people go through the following process to form opinions:.<ref name="Alan">Alan S. & Gary J. (2011). Perception, Attribution, and Judgment of Others. Organizational Behaviour: Understanding and Managing Life at Work Vol. 7</ref>
   
[[Cognition|Cognitive]] theories of perception assume there is a [[poverty of stimulus]]. This (with reference to perception) is the claim that [[sensation]]s are, by themselves, unable to provide a unique description of the world. [[Sensation]]s require 'enriching', which is the role of the mental [[mental model|model]]. A different type of theory is the [[perceptual ecology]] approach of [[J. J. Gibson|James J. Gibson]]. Gibson rejected the assumption of a [[poverty of stimulus]] by rejecting the notion that perception is based in sensations. Instead, he investigated what information is actually presented to the perceptual systems. He (and [http://www.perception-in-action.ed.ac.uk/ the psychologists] who work within this [[paradigm]]) detailed how the world could be specified to a mobile, exploring organism via the lawful projection of information about the world into energy arrays. Specification is a 1:1 mapping of some aspect of the world into a perceptual array; given such a mapping, no enrichment is required and perception is [[direct perception|direct]].
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# When a perceiver encounters an unfamiliar target we are opened different informational cues and want to learn more about the target.
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# In the second step we try to collect more information about the target. Gradually, we encounter some familiar cues which helps us categorize the target.
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# At this stage the cues become less open and selective. We try to search for more cues that confirm the categorization of the target. At this stage we also actively ignore and even distort cues that violate our initial perceptions. Our perception becomes more selective and we finally paint a consistent picture of the target.
   
==Perception as a Unit of Consciousness==
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According to Alan Saks and Gary Johns, there are three components to perception.<ref name="Alan"/>
In [[Objectivism (Ayn Rand)|Objectivist]] [[philosophy]], [[sensations]] are not retained in [[memory]] but the [[object]] of perception is. Perceptions, not sensations, are self-evident "givens." [[Epistemology]] in philosophy is to verify the nature of the perception. To do this, one is first aware of an [[entity]]. The verification process makes an [[identiy]] of it by making [[measurements]], i.e., automatic comparisons. Example: you sense something (entity) that has four legs and a large flat surface (epistemological measurements). Then you compare it to other things of similar appearance and decide it is a table. [[Cognition]][[(perception)]] and measurement (four legs;large flat top) are the primary [[elements]] of [[consciousness]]. The mental [[integration]] of two or more percepts create a [[concept]]{{Fact|date=April 2007}}.
 
   
== Perception-in-Action ==
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# The Perceiver, the person who becomes aware about something and comes to a final understanding. There are 3 factors that can influence his or her perceptions: experience, motivational state and finally emotional state. In different motivational or emotional states, the perceiver will react to or perceive something in different ways. Also in different situations he or she might employ a "perceptual defence" where they tend to "see what they want to see".
The ecological understanding of perception advanced from Gibson's early work is perception-in-action, the notion that perception is a requisite property of animate action, without perception action would not be guided and without action perception would be pointless. Animate actions require perceiving and moving together. In a sense, "perception and movement are two sides of the same coin, the coin is action." [http://www.perception-in-action.ed.ac.uk/People/dave.htm (D.N. Lee)] A mathematical theory of perception-in-action has been devised and investigated in many forms of controlled movement by many different species of organism, [[General Tau Theory]]. According to this theory, tau information, or time-to-goal information is the fundamental 'percept' in perception.
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# The Target. This is the person who is being perceived or judged. "Ambiguity or lack of information about a target leads to a greater need for interpretation and addition."
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# The Situation also greatly influences perceptions because different situations may call for additional information about the target.
   
== Perception and action ==
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Stimuli are not necessarily translated into a percept and rarely does a single stimulus translate into a percept. An ambiguous stimulus may be translated into multiple percepts, experienced randomly, one at a time, in what is called "[[multistable perception]]". And the same stimuli, or absence of them, may result in different percepts depending on subject’s culture and previous experiences. Ambiguous figures demonstrate that a single stimulus can result in more than one percept; for example the [[Rubin vase]] which can be interpreted either as a vase or as two faces. The percept can bind sensations from multiple senses into a whole. A picture of a talking person on a television screen, for example, is bound to the sound of speech from speakers to form a percept of a talking person. "Percept" is also a term used by [[Gottfried Wilhelm Leibniz|Leibniz]],<ref>Leibniz' ''Monadology''</ref> [[Bergson]], [[Deleuze]] and [[Guattari]]<ref>Deleuze and Guattari's ''What is Philosophy?''</ref> to define perception independent from perceivers.
We gather information about the world and interact with it through our actions. Perceptual information is critical for action. Perceptual deficits may lead to profound deficits in action (for touch-perception-related deficits, see [http://www.roblesdelatorre.com/gabriel/GR-IEEE-MM-2006.pdf Robles-De-La-Torre 2006]).
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==Perception and reality==
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In the case of visual perception, some people can actually see the percept shift in their [[mind's eye]].<ref name=Wettlaufer2003>{{Cite book | last = Wettlaufer | first = Alexandra K. | year = 2003 | title = In the mind's eye : the visual impulse in Diderot, Baudelaire and Ruskin, pg. 257 | isbn = 90-420-1035-5 | publisher = Rodopi | location = Amsterdam | postscript = <!--None-->}}</ref> Others, who are not [[Picture thinking|picture thinker]]s, may not necessarily perceive the 'shape-shifting' as their world changes. The 'esemplastic' nature has been shown by experiment: an [[ambiguous image]] has multiple interpretations on the perceptual level.
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This confusing ambiguity of perception is exploited in human technologies such as [[camouflage]], and also in biological [[mimicry]], for example by [[European Peacock|European Peacock butterflies]], whose wings bear eye markings that birds respond to as though they were the eyes of a dangerous predator.
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There is also evidence that the brain in some ways operates on a slight "delay", to allow nerve impulses from distant parts of the body to be integrated into simultaneous signals.<ref>[http://www.npr.org/templates/story/story.php?storyId=104183551 The Secret Advantage Of Being Short] by Robert Krulwich. ''All Things Considered'', NPR. 18 May 2009.</ref>
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Perception is one of the oldest fields in psychology. The oldest quantitative law in psychology is the [[Weber-Fechner law]], which quantifies the relationship between the intensity of physical stimuli and their perceptual effects (for example, testing how much darker a computer screen can get before the viewer actually notices). The study of perception gave rise to the [[Gestalt psychology|Gestalt]] school of psychology, with its emphasis on [[Holism|holistic]] approach.
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==Features==
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===Constancy===
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{{main|Subjective constancy|}}
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''Perceptual constancy'' is the ability of perceptual systems to recognise the same object from widely varying sensory inputs.<ref name="Bernstein2010">{{cite book |last=Bernstein|first=Douglas A.|title=Essentials of Psychology|url=http://books.google.com/books?id=rd77N0KsLVkC&pg=PA119|accessdate=24 March 2011|date=5 March 2010|publisher=Cengage Learning|isbn=978-0-495-90693-3|pages=118–120}}</ref><ref name="AtkinsonAtkinson1990">{{cite book |last1=Atkinson|first1=Rita L.|last2=Atkinson|first2=Richard C.|last3=Smith|first3=Edward E.|title=Introduction to psychology|url=http://books.google.com/books?id=Nw54PwAACAAJ|accessdate=24 March 2011|date=March 1990|publisher=Harcourt Brace Jovanovich|isbn=978-0-15-543689-3|pages=177–183}}</ref> For example, individual people can be recognised from views, such as frontal and profile, which form very different shapes on the retina. A coin looked at face-on makes a circular image on the retina, but when held at angle it makes an elliptical image.<ref name="eop_constancy" /> In normal perception these are recognised as a single three-dimensional object. Without this correction process, an animal approaching from the distance would appear to gain in size.<ref name="Sonderegger1998">{{cite book |last=Sonderegger|first=Theo|title=Psychology|url=http://books.google.com/books?id=UUrCHiSb_QsC&pg=PA45|accessdate=24 March 2011|date=16 October 1998|publisher=John Wiley and Sons|isbn=978-0-8220-5327-9|pages=45–46}}</ref><ref name="enc_constancy" /> One kind of perceptual constancy is ''[[color constancy]]'': for example, a white piece of paper can be recognised as such under different colors and intensities of light.<ref name="enc_constancy">{{cite book |last=Goldstein|first=E. Bruce|editor=E. Bruce Goldstein|title=Encyclopedia of Perception|url=http://books.google.com/books?id=Y4TOEN4f5ZMC&pg=PA309|accessdate=26 March 2011|date=15 October 2009|publisher=Sage|isbn=978-1-4129-4081-8|pages=309–313|chapter=Constancy}}</ref> Another example is ''roughness constancy'': when a hand is drawn quickly across a surface, the touch nerves are stimulated more intensely. The brain compensates for this, so the speed of contact does not affect the perceived roughness.<ref name="enc_constancy" /> Other constancies include melody, odor, brightness and words.<ref name="Roeckelein2006">{{cite book |last=Roeckelein|first=Jon E.|title=Elsevier's dictionary of psychological theories|url=http://books.google.com/books?id=1Yn6NZgxvssC&pg=PA126|accessdate=24 March 2011|year=2006|publisher=Elsevier|isbn=978-0-444-51750-0|page=126}}</ref> These constancies are not always total, but the variation in the percept is much less than the variation in the physical stimulus.<ref name="enc_constancy" /> The perceptual systems of the brain achieve perceptual constancy in a variety of ways, each specialized for the kind of information being processed.<ref name="Yantis2001">{{cite book |last=Yantis|first=Steven|title=Visual perception: essential readings|url=http://books.google.com/books?id=GpGvYSTk9gYC&pg=PA7|accessdate=24 March 2011|year=2001|publisher=Psychology Press|isbn=978-0-86377-598-7|page=7}}</ref>
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===Grouping===
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{{main|Principles of grouping}}
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[[File:Gestalt closure.svg|right|thumb|Law of Closure. The human brain tends to perceive complete shapes even if those forms are incomplete.]]
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The ''principles of grouping'' (or ''Gestalt laws of grouping'') are a set of principles in [[psychology]], first proposed by [[Gestalt psychology|Gestalt psychologists]] to explain how humans naturally perceive objects as organized patterns and objects. Gestalt psychologists argued that these principles exist because the mind has an innate disposition to perceive patterns in the stimulus based on certain rules. These principles are organized into six categories. The principle of ''proximity'' states that, all else being equal, perception tends to group stimuli that are close together as part of the same object, and stimuli that are far apart as two separate objects. The principle of ''similarity'' states that, all else being equal, perception lends itself to seeing stimuli that physically resemble each other as part of the same object, and stimuli that are different as part of a different object. This allows for people to distinguish between adjacent and overlapping objects based on their visual texture and resemblance. The principle of ''closure'' refers to the mind’s tendency to see complete figures or forms even if a picture is incomplete, partially hidden by other objects, or if part of the information needed to make a complete picture in our minds is missing. For example, if part of a shape’s border is missing people still tend to see the shape as completely enclosed by the border and ignore the gaps. The principle of ''good continuation'' makes sense of stimuli that overlap: when there is an intersection between two or more objects, people tend to perceive each as a single uninterrupted object. The principle of ''common fate'' groups stimuli together on the basis of their movement. When visual elements are seen moving in the same direction at the same rate, perception associates the movement as part of the same stimulus. This allows people to make out moving objects even when other details, such as color or outline, are obscured. The principle of ''good form'' refers to the tendency to group together forms of similar shape, pattern, color, etc.<ref>Gray, Peter O. (2006): ''Psychology'', 5th ed., New York: Worth, p. 281. ISBN 978-0-7167-0617-5</ref><ref>{{cite book |ref=harv|chapterurl=http://www.sinauer.com./wolfe/chap4/gestaltF.htm|chapter=Gestalt Grouping Principles|publisher=Sinauer Associates|year=2008|edition=2nd|title=Sensation and Perception|first1=Jeremy M.|last1=Wolfe|first3=Dennis M.|last3=Levi|first2=Keith R.|last2=Kluender|first5=Rachel S.|last5=Herz|first6=Roberta L.|last6=Klatzky|first4=Linda M.|last4=Bartoshuk|first7=Susan J.|last7=Lederman|isbn=978-0-87893-938-1|pages=78, 80}}</ref><ref>Goldstein (2009). pp. 105–107</ref><ref>{{cite encyclopaedia|ref=harv|encyclopedia=Encyclopaedic Dictionary of Psychological Terms|first=J. C.|last=Banerjee|publisher=M.D. Publications Pvt. Ltd|year=1994|isbn10=818588028X|isbn=978-81-85880-28-0|article=Gestalt Theory of Perception|pages=107–108}}</ref> Later research has identified additional grouping principles.<ref>{{cite book |ref=harv|title=Psychology: themes and variations|first=Wayne|last=Weiten|edition=4th|publisher=Brooks/Cole Pub. Co.|year=1998|isbn10=0534340148|isbn=978-0-534-34014-8|page=144}}</ref>
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===Contrast effects===
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{{main|Contrast effect}}
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A common finding across many different kinds of perception is that the perceived qualities of an object can be affected by the qualities of context. If one object is extreme on some dimension, then neighboring objects are perceived as further away from that extreme. "Simultaneous contrast effect" is the term used when stimuli are presented at the same time, whereas "successive contrast" applies when stimuli are presented one after another.<ref name="Corsini2002">{{cite book |last=Corsini|first=Raymond J.|title=The dictionary of psychology|url=http://books.google.com/books?id=0uxnglHzYaoC&pg=PA219|accessdate=24 March 2011|year=2002|publisher=Psychology Press|isbn=978-1-58391-328-4|page=219}}</ref>
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The contrast effect was noted by the 17th Century philosopher [[John Locke]], who observed that lukewarm water can feel hot or cold, depending on whether the hand touching it was previously in hot or cold water.<ref name="Kushner2008">{{cite book |last=Kushner|first=Laura H.|title=Contrast in judgments of mental health|url=http://books.google.com/books?id=TYn5VHp9jioC&pg=PA1|accessdate=24 March 2011|year=2008|publisher=ProQuest|isbn=978-0-549-91314-6|page=1}}</ref> In the early 20th Century, [[Wilhelm Wundt]] identified contrast as a fundamental principle of perception, and since then the effect has been confirmed in many different areas.<ref name="Kushner2008"/> These effects shape not only visual qualities like color and brightness, but other kinds of perception, including how heavy an object feels.<ref name="Plous1993">{{cite book |last=Plous|first=Scott|title=The psychology of judgment and decision making|url=http://books.google.com/books?id=xvWOQgAACAAJ|accessdate=24 March 2011|year=1993|publisher=McGraw-Hill|isbn=978-0-07-050477-6|pages=38–41}}</ref> One experiment found that thinking of the name "Hitler" led to subjects rating a person as more hostile.<ref name="Moskowitz2005">{{cite book |last=Moskowitz|first=Gordon B.|title=Social cognition: understanding self and others|url=http://books.google.com/books?id=_-NLW8Ynvp8C&pg=PA421|accessdate=24 March 2011|year=2005|publisher=Guilford Press|isbn=978-1-59385-085-2|page=421}}</ref> Whether a piece of music is perceived as good or bad can depend on whether the music heard before it was unpleasant or pleasant.<ref name="Popper2010">{{cite book |last=Popper|first=Arthur N.|title=Music Perception|url=http://books.google.com/books?id=ZYXd3CF1_vkC&pg=PA150|accessdate=24 March 2011|date=30 November 2010|publisher=Springer|isbn=978-1-4419-6113-6|page=150}}</ref> For the effect to work, the objects being compared need to be similar to each other: a television reporter can seem smaller when interviewing a tall basketball player, but not when standing next to a tall building.<ref name="Plous1993"/>
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==Effect of experience==
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{{main|Perceptual learning}}
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With experience, organisms can learn to make finer perceptual distinctions, and learn new kinds of categorization. Wine-tasting, the reading of X-ray images and music appreciation are applications of this process in the human sphere. Research has focused on the relation of this to other kinds of learning, and whether it takes place in peripheral sensory systems or in the brain's processing of sense information. {{Citation needed|date=July 2011}}
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==Effect of motivation and expectation==
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{{main|Set (psychology)}}
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A ''perceptual set'', also called ''perceptual expectancy'' or just ''set'' is a predisposition to perceive things in a certain way.<ref name="Weiten2008">{{cite book |last=Weiten|first=Wayne|title=Psychology: Themes and Variations|url=http://books.google.com/books?id=sILajOhJpOsC&pg=PT193|accessdate=24 March 2011|date=17 December 2008|publisher=Cengage Learning|isbn=978-0-495-60197-5|page=193}}</ref> It is an example of how perception can be shaped by "top-down" processes such as drives and expectations.<ref name="CoonMitterer2008">{{cite book |last1=Coon|first1=Dennis|last2=Mitterer|first2=John O.|title=Introduction to Psychology: Gateways to Mind and Behavior|url=http://books.google.com/books?id=vw20LEaJe10C&pg=PA171|accessdate=24 March 2011|date=29 December 2008|publisher=Cengage Learning|isbn=978-0-495-59911-1|pages=171–172}}</ref> Perceptual sets occur in all the different senses.<ref name="Sonderegger1998">{{cite book |last=Sonderegger|first=Theo|title=Psychology|url=http://books.google.com/books?id=UUrCHiSb_QsC&pg=PA43|accessdate=24 March 2011|date=16 October 1998|publisher=John Wiley and Sons|isbn=978-0-8220-5327-9|pages=43–44}}</ref> They can be long term, such as a special sensitivity to hearing one's own name in a crowded room, or short term, as in the ease with which hungry people notice the smell of food.<ref name="HardyHeyes1999">{{cite book |last1=Hardy|first1=Malcolm|last2=Heyes|first2=Steve|title=Beginning Psychology|url=http://books.google.com/books?id=fjPWqXi9WQsC&pg=PA24|accessdate=24 March 2011|date=2 December 1999|publisher=Oxford University Press|isbn=978-0-19-832821-6|pages=24–27}}</ref> A simple demonstration of the effect involved very brief presentations of non-words such as "sael". Subjects who were told to expect words about animals read it as "seal", but others who were expecting boat-related words read it as "sail".<ref name="HardyHeyes1999"/>
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Sets can be created by [[motivation]] and so can result in people interpreting ambiguous figures so that they see what they want to see.<ref name="CoonMitterer2008"/> For instance, how someone perceives what unfolds during a sports game can be biased if they strongly support one of the teams.<ref name="BlockYuker2002">{{cite book |last1=Block|first1=J. R.|last2=Yuker|first2=Harold E.|title=Can You Believe Your Eyes?: Over 250 Illusions and Other Visual Oddities|url=http://books.google.com/books?id=uNMFiMQu8BMC&pg=PA173|accessdate=24 March 2011|date=1 October 2002|publisher=Robson|isbn=978-1-86105-586-6|pages=173–174}}</ref> In one experiment, students were allocated to pleasant or unpleasant tasks by a computer. They were told that either a number or a letter would flash on the screen to say whether they were going to taste an orange juice drink or an unpleasant-tasting health drink. In fact, an ambiguous figure was flashed on screen, which could either be read as the letter B or the number 13. When the letters were associated with the pleasant task, subjects were more likely to perceive a letter B, and when letters were associated with the unpleasant task they tended to perceive a number 13.<ref name="Weiten2008"/>
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Perceptual set has been demonstrated in many social contexts. People who are primed to think of someone as "warm" are more likely to perceive a variety of positive characteristics in them, than if the word "warm" is replaced by "cold". When someone has a reputation for being funny, an audience are more likely to find them amusing.<ref name="HardyHeyes1999"/> Individual's perceptual sets reflect their own personality traits. For example, people with an aggressive personality are quicker to correctly identify aggressive words or situations.<ref name="HardyHeyes1999"/>
  +
  +
One classic psychological experiment showed slower reaction times and less accurate answers when a deck of [[playing cards]] reversed the color of the [[Suit (cards)|suit]] symbol for some cards (e.g. red spades and black hearts).<ref>"On the Perception of Incongruity: A Paradigm" by Jerome S. Bruner and Leo Postman. ''Journal of Personality'', 18, pp. 206-223. 1949. [http://psychclassics.yorku.ca/Bruner/Cards/ Yorku.ca]</ref>
  +
  +
Philosopher [[Andy Clark]] explains that perception, although it occurs quickly, is not simply a bottom-up process (where minute details are put together to form larger wholes). Instead, our brains use what he calls ''[[Predictive coding]]''. It starts with very broad constraints and expectations for the state of the world, and as expectations are met, it makes more detailed predictions (errors lead to new predictions, or [[learning]] processes). Clark says this research has various implications; not only can there be no completely "unbiased, unfiltered" perception, but this means that there is a great deal of feedback between perception and expectation (perceptual experiences often shape our beliefs, but those perceptions were based on existing beliefs).<ref>{{cite web|url= http://www.edge.org/q2011/q11_6.html|title= Predictive Coding}}</ref>
  +
  +
==Theories==
  +
  +
===Perception as direct perception===
  +
[[Cognitivism (psychology)|Cognitive theories]] of perception assume there is a poverty of [[Stimulus (physiology)|stimulus]]. This (with reference to perception) is the claim that [[Wikt:sensation|sensations]] are, by themselves, unable to provide a unique description of the world.
  +
"<ref>Stone, James V. (2012): "Vision and Brain: How we perceive the world", Cambridge, MIT Press, pp. 155-178.</ref> Sensations require 'enriching', which is the role of the mental model. A different type of theory is the perceptual [[ecology]] approach of [[James J. Gibson]]. Gibson rejected the assumption of a [[poverty of stimulus]] by rejecting the notion that perception is based upon sensations&nbsp;– instead, he investigated what information is actually presented to the perceptual systems. His theory "assumes the existence of stable, unbounded, and permanent stimulus-information in the ambient optic array. And it supposes that the visual system can explore and detect this information. The theory is information-based, not sensation-based."<ref>Gibson, James J. (2002): "A Theory of Direct Visual Perception". In: Alva Noë/Evan Thompson (Eds.), ''Vision and Mind. Selected Readings in the Philosophy of Perception'', Cambridge, MIT Press, pp. 77–89.</ref> He and the psychologists who work within this [[paradigm]] detailed how the world could be specified to a mobile, exploring organism via the lawful projection of information about the world into energy arrays.<ref>{{cite book |last=Sokolowski|first=Robert|title=Phenomenology of the Human Person|year=2008|publisher=Cambridge University Press|location=New York|isbn=978-0521717663|pages=199–200|url=http://books.google.com/books?id=NIEJt5afhwgC&printsec=frontcover#v=onepage&q&f=false}}</ref> Specification is a 1:1 mapping of some aspect of the world into a perceptual array; given such a mapping, no enrichment is required and perception is [[direct perception]].<ref>{{cite journal |last=Richards|first=Robert J.|title=James Gibson's Passive Theory of Perception: A Rejection of the Doctrine of Specific Nerve Energies|journal=Philosophy and Phenomenological Research|date=December 1976|volume=37|issue=2|pages=218–233|url=http://philosophy.uchicago.edu/faculty/files/richards/James%20Gibson's%20Passive%20Theory%20of%20Perception.pdf}}</ref>
  +
  +
===Perception-in-action===
  +
An ecological understanding of perception derived from Gibson's early work is that of "perception-in-action", the notion that perception is a requisite property of animate action; that without perception action would be unguided, and without action perception would serve no purpose. Animate actions require both perception and motion, and perception and movement can be described as "two sides of the same coin, the coin is action". Gibson works from the assumption that singular entities, which he calls "invariants", already exist in the real world and that all that the perception process does is to home in upon them. A view known as [[Constructivist epistemology|constructivism]] (held by such philosophers as [[Ernst von Glasersfeld]]) regards the continual adjustment of perception and action to the external input as precisely what constitutes the "entity", which is therefore far from being invariant.<ref>Consciousness in Action, S. L. Hurley, illustrated, Harvard University Press, 2002, 0674007964, pg. 430-432,</ref>
  +
  +
Glasersfeld considers an "invariant" as a target to be homed in upon, and a pragmatic necessity to allow an initial measure of understanding to be established prior to the updating that a statement aims to achieve. The invariant does not and need not represent an actuality, and Glasersfeld describes it as extremely unlikely that what is desired or [[fear processing in the brain|fear]]ed by an organism will never suffer change as time goes on. This social constructionist theory thus allows for a needful evolutionary adjustment.<ref>Glasersfeld, Ernst von (1995), ''Radical Constructivism: A Way of Knowing and Learning,'' London: RoutledgeFalmer; Poerksen, Bernhard (ed.) (2004), ''The Certainty of Uncertainty: Dialogues Introducing Constructivism,'' Exeter: Imprint Academic; Wright. Edmond (2005). ''Narrative, Perception, Language, and Faith,'' Basingstoke: [[Palgrave Macmillan]].</ref>
  +
  +
A mathematical theory of perception-in-action has been devised and investigated in many forms of controlled movement, and has been described in many different species of organism using the [[General Tau Theory]]. According to this theory, tau information, or time-to-goal information is the fundamental 'percept' in perception.
  +
  +
===Evolutionary psychology and perception===
  +
Many philosophers, such as Jerry Fodor, write that the purpose of perception is knowledge, but evolutionary psychologists hold that its primary purpose is to guide action.<ref name = "Gaulin 4"/> For example, they say, depth perception seems to have evolved not to help us know the distances to other objects but rather to help us move around in space.<ref name = "Gaulin 4"/> Evolutionary psychologists say that animals from fiddler crabs to humans use eyesight for collision avoidance, suggesting that vision is basically for directing action, not providing knowledge.<ref name = "Gaulin 4">Gaulin, Steven J. C. and Donald H. McBurney. Evolutionary Psychology. Prentice Hall. 2003. ISBN 978-0-13-111529-3, Chapter 4, p 81-101.</ref>
  +
  +
Building and maintaining sense organs is metabolically expensive, so these organs evolve only when they improve an organism's fitness.<ref name = "Gaulin 4"/> More than half the brain is devoted to processing sensory information, and the brain itself consumes roughly one-fourth of one's metabolic resources, so the senses must provide exceptional benefits to fitness.<ref name = "Gaulin 4"/> Perception accurately mirrors the world; animals get useful, accurate information through their senses.<ref name = "Gaulin 4"/>
  +
  +
Scientists who study perception and sensation have long understood the human senses as adaptations.<ref name = "Gaulin 4"/> Depth perception consists of processing over half a dozen visual cues, each of which is based on a regularity of the physical world.<ref name = "Gaulin 4"/> Vision evolved to respond to the narrow range of electromagnetic energy that is plentiful and that does not pass through objects.<ref name = "Gaulin 4"/> Sound waves provide useful information about the sources of and distances to objects, with larger animals making and hearing lower-frequency sounds and smaller animals making and hearing higher-frequency sounds.<ref name = "Gaulin 4"/> Taste and smell respond to chemicals in the environment that were significant for fitness in the EEA.<ref name = "Gaulin 4"/> The sense of touch is actually many senses, including pressure, heat, cold, tickle, and pain.<ref name = "Gaulin 4"/> Pain, while unpleasant, is adaptive.<ref name = "Gaulin 4"/> An important adaptation for senses is range shifting, by which the organism becomes temporarily more or less sensitive to sensation.<ref name = "Gaulin 4"/> For example, one's eyes automatically adjust to dim or bright ambient light.<ref name = "Gaulin 4"/> Sensory abilities of different organisms often coevolve, as is the case with the hearing of echolocating bats and that of the moths that have evolved to respond to the sounds that the bats make.<ref name = "Gaulin 4"/>
  +
  +
Evolutionary psychologists claim that perception demonstrates the principle of modularity, with specialized mechanisms handling particular perception tasks.<ref name = "Gaulin 4"/> For example, people with damage to a particular part of the brain suffer from the specific defect of not being able to recognize faces (prospagnosia).<ref name = "Gaulin 4"/> EP suggests that this indicates a so-called face-reading module.<ref name = "Gaulin 4"/>
  +
  +
===Theories of visual perception===
  +
* [[Empirical theories of perception]]
  +
* [[Feature integration theory|Anne Treisman's feature integration theory]]
  +
* [[Interactive activation and competition networks|Interactive activation and competition]]
  +
* [[Recognition by Components Theory|Irving Biederman's recognition by components theory]]
  +
  +
==Physiology==
  +
{{main|Sensory system}}
  +
A ''sensory system'' is a part of the nervous system responsible for processing [[sense|sensory]] information. A sensory system consists of [[sensory receptor]]s, [[neural pathway]]s, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for [[vision (sense)|vision]], [[hearing (sense)|hearing]], [[somatic sensation]] (touch), [[taste]] and [[olfaction]] (smell). It has been suggested that the immune system is an overlooked sensory modlality.<ref>Bedford,F.L. (2011). The missing sensory modality: the immune system. Perception, 40, 1265-1267 {{doi|10.1068/p7119}} http://www.perceptionweb.com/abstract.cgi?id=p7119</ref> In short, senses are [[transducers]] from the physical world to the realm of the mind.
  +
  +
The [[receptive field]] is the specific part of the world to which a receptor organ and receptor cells respond. For instance, the part of the world an eye can see, is its receptive field; the light that each [[Rod cell|rod]] or [[Cone cell|cone]] can see, is its receptive field.<ref>Kolb & Whishaw: ''Fundamentals of Human Neuropsychology'' (2003)</ref> Receptive fields have been identified for the [[visual system]], [[auditory system]] and [[somatosensory system]], so far.
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==Types==
  +
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===Of sound===
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[[File:Anatomy of the Human Ear.svg|thumb|right|Anatomy of the human ear. (The length of the auditory canal is exaggerated in this image)]]
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{{main|Hearing (sense)}}
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Hearing (or ''audition'') is the ability to perceive [[sound]] by detecting [[vibration]]s. Frequencies capable of being heard by humans are called [[Audio frequency|audio]] or ''sonic''. The range is typically considered to be between 20&nbsp;[[Hertz|Hz]] and 20,000&nbsp;Hz.<ref>{{cite web | url = http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml | title = Frequency Range of Human Hearing | work = The Physics Factbook}}</ref> Frequencies higher than audio are referred to as [[ultrasound|ultrasonic]], while frequencies below audio are referred to as [[infrasound|infrasonic]]. The [[auditory system]] includes the [[ear]]s and inner structures which produce neural signals in response to the sound. The [[primary auditory cortex]], within the [[temporal lobe]] of the human brain, is where auditory information arrives in the [[cerebral cortex]].
  +
  +
Sound does not usually come from a single source: in real situations, sounds from multiple sources and directions are superimposed as they arrive at the ears. Hearing involves the computationally complex task of separating out the sources of interest, often estimating their distance and direction as well as identifying them.<ref name="eop_constancy"/>
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====Of speech====
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{{main|Speech perception}}
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[[File:Spectrogram of I owe you.png|right|thumb|300px|Though the phrase "I owe you" can be heard as three distinct words, a [[spectrogram]] reveals no clear boundaries.]]
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''Speech perception'' is the process by which the sounds of language are heard, interpreted and understood. Research in speech perception seeks to understand how human listeners recognize speech sounds and use this information to understand spoken language. The sound of a word can vary widely according to words around it and the tempo of the speech, as well as the physical characteristics, [[Accent (dialect)|accent]] and mood of the speaker. Listeners manage to perceive words across this wide range of different conditions.{{Citation needed|date=March 2011}} Another variation is that [[reverberation]] can make a large difference in sound between a word spoken from the far side of a room and the same word spoken up close. Experiments have shown that people automatically compensate for this effect when hearing speech.<ref name="eop_constancy">{{cite book |first=Brian C. J.|last=Moore|editor-last=Goldstein|editor-first=E. Bruce|title=Encyclopedia of Perception|url=http://books.google.com/books?id=Y4TOEN4f5ZMC&pg=PA136|accessdate=26 March 2011|date=15 October 2009|publisher=Sage|isbn=978-1-4129-4081-8|pages=136–137|chapter=Audition}}</ref><ref name="Watkins2010">{{cite book |last1=Watkins|first1=Anthony J.|last2=Raimond|first2=Andrew|last3=Makin|first3=Simon J.|editor=Enrique A. Lopez-Poveda|title=The Neurophysiological Bases of Auditory Perception|url=http://books.google.com/books?id=ACkNL-G7gUUC&pg=PA440|accessdate=26 March 2011|date=23 March 2010|publisher=Springer|isbn=978-1-4419-5685-9|page=440|chapter=Room reflection and constancy in speech-like sounds: Within-band effects}}</ref>
  +
  +
The process of perceiving speech begins at the level of the sound within the auditory signal and the process of [[Hearing (sense)|audition]]. After processing the initial auditory signal, speech sounds are further processed to extract acoustic cues and phonetic information. This speech information can then be used for higher-level language processes, such as word recognition. Speech perception is not necessarily uni-directional. That is, higher-level language processes connected with [[morphology (linguistics)|morphology]], [[syntax]], or [[semantics]] may interact with basic speech perception processes to aid in recognition of speech sounds.{{Citation needed|date=March 2011}} It may be the case that it is not necessary and maybe even not possible for a listener to recognize phonemes before recognizing higher units, like words for example. In one experiment, Richard M. Warren replaced one phoneme of a word with a cough-like sound. His subjects restored the missing speech sound perceptually without any difficulty and what is more, they were not able to identify accurately which phoneme had been disturbed.<ref>{{cite journal |author=Warren, R.M. |year=1970 |title=Restoration of missing speech sounds |journal=Science |volume=167 |pages=392–393 |doi=10.1126/science.167.3917.392 |pmid=5409744 |issue=3917}}</ref>
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  +
===Touch===
  +
{{main|Haptic perception}}
  +
''Haptic perception'' is the process of recognizing objects through touch. It involves a combination of [[somatosensory]] perception of patterns on the skin surface (e.g., edges, curvature, and texture) and [[proprioception]] of hand position and conformation. People can rapidly and accurately identify three-dimensional objects by touch.<ref>{{cite journal |author=Klatzky RL, Lederman SJ, & Metzger VA |year=1985 |title=Identifying objects by touch: An "expert system." |journal=Perception & Psychophysics |issue = 37 |pages=299–302 |doi=10.3758/BF03211351 |volume=37}}</ref> This involves exploratory procedures, such as moving the fingers over the outer surface of the object or holding the entire object in the hand.<ref>{{cite journal |author=Lederman SJ, & Klatzky RL |year=1987 |title=Hand movements: A window into haptic object recognition |journal=Cognitive Psychology |issue=3 |pages=342–368 |doi=10.1016/0010-0285(87)90008-9 |volume=19 |pmid=3608405}}</ref> Haptic perception relies on the forces experienced during touch.<ref name=Robles-de-la-torre2001>{{Cite journal | last1 = Robles-de-la-torre | first1 = Gabriel | last2 = Hayward | first2 = Vincent | year = 2001 | title = Force can overcome object geometry in the perception of shape through active touch | journal = Nature | pmid = 11473320 | volume = 412 | issue = 6845 | pages = 445–448 | doi = 10.1038/35086588}}</ref>
  +
  +
Gibson defined the haptic system as "The sensibility of the individual to the world adjacent to his body by use of his body".<ref>{{cite book |last=Gibson |first=J.J. |year=1966 |title=The senses considered as perceptual systems. |location=Boston |publisher=Houghton Mifflin |isbn=0-313-23961-4}}</ref> Gibson and others emphasized the close link between haptic perception and body movement: haptic perception is active exploration. The concept of haptic perception is related to the concept of [[extended physiological proprioception]] according to which, when using a tool such as a stick, perceptual experience is transparently transferred to the end of the tool.
  +
  +
===Taste===
  +
{{main|Taste}}
  +
Taste (or, the more formal term, ''gustation'') is the ability to perceive the [[flavor]] of substances including, but not limited to, [[food]]. Humans receive tastes through sensory organs called ''[[taste bud]]s'', or ''gustatory calyculi'', concentrated on the upper surface of the [[tongue]].<ref>[http://books.google.com/books?id=dNhFLnc6NRkC&lpg=PA201 Human biology (Page 201/464)] Daniel D. Chiras. Jones & Bartlett Learning, 2005.</ref> The human tongue has 100 to 150 taste receptor cells on each of its roughly ten thousand taste buds.<ref name="DeVereCalvert2010_39">{{cite book |last1=DeVere|first1=Ronald|last2=Calvert|first2=Marjorie|title=Navigating Smell and Taste Disorders|url=http://books.google.com/books?id=m6WOtX2QAtwC&pg=PA39|accessdate=26 March 2011|date=31 August 2010|publisher=Demos Medical Publishing|isbn=978-1-932603-96-5|pages=39–40}}</ref> There are five primary tastes: [[sweetness]], [[Bitter_(taste)#Bitter|bitterness]], [[sourness]], [[saltiness]], and [[umami]]. Other tastes can be mimicked by combining these basic tastes.<ref name="DeVereCalvert2010_39"/><ref name="SiegelAlbers2006"/> The recognition and awareness of umami is a relatively recent development in [[Western cuisine]].<ref>
  +
*[http://www.foxnews.com/leisure/2010/01/05/oh-mama-whats-umami/ Oh, Mama, What's Up With Umami?] foxnews.com, January 05, 2010
  +
*[http://www.trendcentral.com/life/umami-dearest/ Umami Dearest: The mysterious fifth taste has dfficially infiltrated the food scene] trendcentral.com, Feb 23rd, 2010
  +
*[http://www.foodchannel.com/articles/article/8-food-trend-for-2010-i-want-my-umami/ #8 Food Trend for 2010: I Want My Umami] foodchannel.com, Dec. 06, 2009</ref> The basic tastes contribute only partially to the sensation and [[flavor]] of food in the mouth&nbsp;— other factors include [[Odor|smell]], detected by the [[olfactory epithelium]] of the nose;<ref name="DeVereCalvert2010_33">{{cite book |last1=DeVere|first1=Ronald|last2=Calvert|first2=Marjorie|title=Navigating Smell and Taste Disorders|url=http://books.google.com/books?id=m6WOtX2QAtwC&pg=PA39|accessdate=26 March 2011|date=31 August 2010|publisher=Demos Medical Publishing|isbn=978-1-932603-96-5|pages=33–37}}</ref> [[Texture (food)|texture]], detected through a variety of [[mechanoreceptor]]s, muscle nerves, etc.;<ref name="SiegelAlbers2006"/><ref>[http://books.google.com/books?id=aJBIbvClWfcC&lpg=PP1&dq=Food%20texture&pg=PA4#v=onepage&q&f=false Food texture: measurement and perception (page 3–4/311)] Andrew J. Rosenthal. Springer, 1999.</ref> and temperature, detected by [[thermoreceptor]]s.<ref name="SiegelAlbers2006">{{cite book |last1=Siegel|first1=George J.|last2=Albers|first2=R. Wayne|title=Basic neurochemistry: molecular, cellular, and medical aspects|url=http://books.google.com/books?id=Af0IyHtGCMUC&pg=PA825|accessdate=26 March 2011|year=2006|publisher=Academic Press|isbn=978-0-12-088397-4|page=825}}</ref> All basic tastes are classified as either ''appetitive'' or ''aversive'', depending upon whether the things they sense are harmful or beneficial.<ref name=aa>[http://www.scientificamerican.com/article.cfm?id=two-great-tastes-not-great-together Why do two great tastes sometimes not taste great together?] scientificamerican.com. Dr. Tim Jacob, Cardiff University. May 22, 2009.</ref>
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  +
===Other senses===
  +
{{main|Sense}}
  +
Other senses enable perception of body balance, acceleration, gravity, position of body parts, temperature, pain, time, and perception of internal senses such as suffocation, gag reflex, intestinal distension, fullness of rectum and urinary bladder, and sensations felt in the throat and lungs.
  +
  +
===Of the social world===
  +
{{main|Social perception}}
  +
''Social perception'' is the part of perception that allows people to understand the individuals and groups of their social world, and thus an element of [[social cognition]].<ref>E. R. Smith, D. M. Mackie (2000). ''Social Psychology''. Psychology Press, 2nd ed., p. 20</ref>
   
 
== Types of sensory perception==
 
== Types of sensory perception==
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== See also ==
 
== See also ==
  +
{{col-begin}}
  +
{{col-2}}
  +
* [[Action-specific perception]]
 
* [[Apophenia]]
 
* [[Apophenia]]
 
* [[Apperception]]
 
* [[Apperception]]
 
* [[Attention]]
 
* [[Attention]]
 
* [[Autopoiesis]]
 
* [[Autopoiesis]]
  +
* [[Change blindness]]
 
* [[Constructivism]]
 
* [[Constructivism]]
 
* [[Deregowski's Cross-Cultural Study on Perception]]
 
* [[Deregowski's Cross-Cultural Study on Perception]]
Line 75: Line 79:
 
* [[Object recognition]]
 
* [[Object recognition]]
 
* [[Pareidolia]]
 
* [[Pareidolia]]
  +
{{col-2}}
 
* [[Perceptual closure]]
 
* [[Perceptual closure]]
 
* [[Perceptual constancy]]
 
* [[Perceptual constancy]]
Line 91: Line 96:
 
* [[Priming]]
 
* [[Priming]]
 
* [[Psychophysics]]
 
* [[Psychophysics]]
  +
* [[Qualia]]
 
* [[Rhythym]]
 
* [[Rhythym]]
 
* [[Sensory gating]]
 
* [[Sensory gating]]
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* [[Sensory neuroscience]]
 
* [[Sensory neuroscience]]
 
* [[Visual routine]]
 
* [[Visual routine]]
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{{Multicol-end}}
   
==References & Bibliography==
+
==Notes==
  +
{{Reflist|20em}}
  +
  +
==References==
  +
{{Refbegin}}
  +
*{{cite book |last=Goldstein|first=E. Bruce|title=Sensation and perception|url=http://books.google.com/books?id=2tW91BWeNq4C|accessdate=26 March 2011|date=13 February 2009|year=2009a|publisher=Cengage Learning|isbn=978-0-495-60149-4|ref=harv}}
  +
*{{cite book |last1=Gregory|first1=Richard L.|last2=Zangwill|first2=O. L.|title=The Oxford companion to the mind|url=http://books.google.com/books?id=HRYoSwAACAAJ|accessdate=24 March 2011|year=1987|publisher=Oxford University Press|ref=harv}}
  +
{{Refend}}
  +
  +
==Further reading==
 
==Key texts==
 
==Key texts==
 
===Books===
 
===Books===
  +
*Arnheim, R. (1969). Visual Thinking. Berkeley: University of California Press. ISBN 978-0-520-24226-5.
  +
*Gibson, J. J. (1966). ''The Senses Considered as Perceptual Systems''.
  +
*Gibson, J. J. (1987). ''The Ecological Approach to Visual Perception''. Lawrence Erlbaum Associates. ISBN 0-89859-959-8
 
*Goldstein, Sensation & Perception ISBN 0-534-09026-5 ISBN 0-534-13723-7
 
*Goldstein, Sensation & Perception ISBN 0-534-09026-5 ISBN 0-534-13723-7
 
*Goldstein, Sensation & Perception, Media Edition ISBN 0-534-13741-5 ISBN 0-534-13714-8
 
*Goldstein, Sensation & Perception, Media Edition ISBN 0-534-13741-5 ISBN 0-534-13714-8
* James J. Gibson. ''The Ecological Approach to Visual Perception''. Lawrence Erlbaum Associates, 1987. ISBN 0898599598
+
*James J. Gibson. ''The Ecological Approach to Visual Perception''. Lawrence Erlbaum Associates, 1987. ISBN 0898599598
   
 
===Papers===
 
===Papers===
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* Robles-De-La-Torre G. & Hayward V. [http://www.roblesdelatorre.com/gabriel/GR-VH-Nature2001.pdf Force Can Overcome Object Geometry In the perception of Shape Through Active Touch]. Nature 412 (6845):445-8 (2001).
 
* Robles-De-La-Torre G. & Hayward V. [http://www.roblesdelatorre.com/gabriel/GR-VH-Nature2001.pdf Force Can Overcome Object Geometry In the perception of Shape Through Active Touch]. Nature 412 (6845):445-8 (2001).
 
* Robles-De-La-Torre G. [http://www.roblesdelatorre.com/gabriel/GR-IEEE-MM-2006.pdf The Importance of the Sense of Touch in Virtual and Real Environments]. IEEE Multimedia 13(3), Special issue on Haptic User Interfaces for Multimedia Systems, pp. 24-30 (2006).
 
* Robles-De-La-Torre G. [http://www.roblesdelatorre.com/gabriel/GR-IEEE-MM-2006.pdf The Importance of the Sense of Touch in Virtual and Real Environments]. IEEE Multimedia 13(3), Special issue on Haptic User Interfaces for Multimedia Systems, pp. 24-30 (2006).
  +
 
==External links==
 
==External links==
 
*[http://consc.net/online1.html#perception Online papers on perception], by various authors, compiled by [[David Chalmers]]
 
*[http://consc.net/online1.html#perception Online papers on perception], by various authors, compiled by [[David Chalmers]]
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* [http://www.technologyreview.com/read_article.aspx?id=17363&ch=biotech&sc=&pg=1 The Cutting Edge of Haptics], by Duncan Graham-Rowe.
 
* [http://www.technologyreview.com/read_article.aspx?id=17363&ch=biotech&sc=&pg=1 The Cutting Edge of Haptics], by Duncan Graham-Rowe.
 
* [http://www.simplypsychology.pwp.blueyonder.co.uk/perception-theories.html Theories of Perception]
 
* [http://www.simplypsychology.pwp.blueyonder.co.uk/perception-theories.html Theories of Perception]
  +
* [http://www.richardgregory.org/ Richard L Gregory] Theories of Richard. L. Gregory.
  +
*[http://www.michaelbach.de/ot/ Comprehensive set of optical illusions, presented by Michael Bach].
  +
* [http://www.optillusions.com/ Optical Illusions] Examples of well-known optical illusions.
   
 
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Please copy and paste this prompt to other appropriate areas. Feel free to edit as necessary

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For the journal of the same name, see Perception (journal)

Perception (from the Latin perceptio, percipio) is the organization, identification, and interpretation of sensory information in order to represent and understand the environment.[1] All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs.[2] For example, vision involves light striking the retinas of the eyes, smell is mediated by odor molecules and hearing involves pressure waves. Perception is not the passive receipt of these signals, but can be shaped by learning, memory, and expectation.[3][4] Perception involves these "top-down" effects as well as the "bottom-up" process of processing sensory input.[4] The "bottom-up" processing is basically low-level information that's used to build up higher-level information (e.g., shapes for object recognition). The "top-down" processing refers to a person's concept and expectations (knowledge) that influence perception. Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness.[2]

Since the rise of experimental psychology in the late 19th Century, psychology's understanding of perception has progressed by combining a variety of techniques.[3] Psychophysics measures the effect on perception of varying the physical qualities of the input. Sensory neuroscience studies the brain mechanisms underlying perception. Perceptual systems can also be studied computationally, in terms of the information they process. Perceptual issues in philosophy include the extent to which sensory qualities such as sounds, smells or colors exist in objective reality rather than the mind of the perceiver.[3]

Although the senses were traditionally viewed as passive receptors, the study of illusions and ambiguous images has demonstrated that the brain's perceptual systems actively and pre-consciously attempt to make sense of their input.[3] There is still active debate about the extent to which perception is an active process of hypothesis testing, analogous to science, or whether realistic sensory information is rich enough to make this process unnecessary.[3]

The perceptual systems of the brain enable individuals to see the world around them as stable, even though the sensory information may be incomplete and rapidly varying. Human and animal brains are structured in a modular way, with different areas processing different kinds of sensory information. Some of these modules take the form of sensory maps, mapping some aspect of the world across part of the brain's surface. These different modules are interconnected and influence each other. For instance, the taste is strongly influenced by its odor.[5]

Process and terminology

The process of perception begins with an object in the real world, termed the distal stimulus or distal object.[2] By means of light, sound or another physical process, the object stimulates the body's sensory organs. These sensory organs transform the input energy into neural activity—a process called transduction.[2][6] This raw pattern of neural activity is called the proximal stimulus.[2] These neural signals are transmitted to the brain and processed.[2] The resulting mental re-creation of the distal stimulus is the percept. Perception is sometimes described as the process of constructing mental representations of distal stimuli using the information available in proximal stimuli.

An example would be a person looking at a shoe. The shoe itself is the distal stimulus. When light from the shoe enters a person's eye and stimulates their retina, that stimulation is the proximal stimulus.[7] The image of the shoe reconstructed by the brain of the person is the percept. Another example would be a telephone ringing. The ringing of the telephone is the distal stimulus. The sound stimulating a person's auditory receptors is the proximal stimulus, and the brain's interpretation of this as the ringing of a telephone is the percept. The different kinds of sensation such as warmth, sound, and taste are called "sensory modalities".[6][8]

Psychologist Jerome Bruner has developed a model of perception. According to him people go through the following process to form opinions:.[9]

  1. When a perceiver encounters an unfamiliar target we are opened different informational cues and want to learn more about the target.
  2. In the second step we try to collect more information about the target. Gradually, we encounter some familiar cues which helps us categorize the target.
  3. At this stage the cues become less open and selective. We try to search for more cues that confirm the categorization of the target. At this stage we also actively ignore and even distort cues that violate our initial perceptions. Our perception becomes more selective and we finally paint a consistent picture of the target.

According to Alan Saks and Gary Johns, there are three components to perception.[9]

  1. The Perceiver, the person who becomes aware about something and comes to a final understanding. There are 3 factors that can influence his or her perceptions: experience, motivational state and finally emotional state. In different motivational or emotional states, the perceiver will react to or perceive something in different ways. Also in different situations he or she might employ a "perceptual defence" where they tend to "see what they want to see".
  2. The Target. This is the person who is being perceived or judged. "Ambiguity or lack of information about a target leads to a greater need for interpretation and addition."
  3. The Situation also greatly influences perceptions because different situations may call for additional information about the target.

Stimuli are not necessarily translated into a percept and rarely does a single stimulus translate into a percept. An ambiguous stimulus may be translated into multiple percepts, experienced randomly, one at a time, in what is called "multistable perception". And the same stimuli, or absence of them, may result in different percepts depending on subject’s culture and previous experiences. Ambiguous figures demonstrate that a single stimulus can result in more than one percept; for example the Rubin vase which can be interpreted either as a vase or as two faces. The percept can bind sensations from multiple senses into a whole. A picture of a talking person on a television screen, for example, is bound to the sound of speech from speakers to form a percept of a talking person. "Percept" is also a term used by Leibniz,[10] Bergson, Deleuze and Guattari[11] to define perception independent from perceivers.

Perception and reality

In the case of visual perception, some people can actually see the percept shift in their mind's eye.[12] Others, who are not picture thinkers, may not necessarily perceive the 'shape-shifting' as their world changes. The 'esemplastic' nature has been shown by experiment: an ambiguous image has multiple interpretations on the perceptual level.

This confusing ambiguity of perception is exploited in human technologies such as camouflage, and also in biological mimicry, for example by European Peacock butterflies, whose wings bear eye markings that birds respond to as though they were the eyes of a dangerous predator.

There is also evidence that the brain in some ways operates on a slight "delay", to allow nerve impulses from distant parts of the body to be integrated into simultaneous signals.[13]

Perception is one of the oldest fields in psychology. The oldest quantitative law in psychology is the Weber-Fechner law, which quantifies the relationship between the intensity of physical stimuli and their perceptual effects (for example, testing how much darker a computer screen can get before the viewer actually notices). The study of perception gave rise to the Gestalt school of psychology, with its emphasis on holistic approach.

Features

Constancy

Main article: Subjective constancy

Perceptual constancy is the ability of perceptual systems to recognise the same object from widely varying sensory inputs.[4][14] For example, individual people can be recognised from views, such as frontal and profile, which form very different shapes on the retina. A coin looked at face-on makes a circular image on the retina, but when held at angle it makes an elliptical image.[15] In normal perception these are recognised as a single three-dimensional object. Without this correction process, an animal approaching from the distance would appear to gain in size.[16][17] One kind of perceptual constancy is color constancy: for example, a white piece of paper can be recognised as such under different colors and intensities of light.[17] Another example is roughness constancy: when a hand is drawn quickly across a surface, the touch nerves are stimulated more intensely. The brain compensates for this, so the speed of contact does not affect the perceived roughness.[17] Other constancies include melody, odor, brightness and words.[18] These constancies are not always total, but the variation in the percept is much less than the variation in the physical stimulus.[17] The perceptual systems of the brain achieve perceptual constancy in a variety of ways, each specialized for the kind of information being processed.[19]

Grouping

Main article: Principles of grouping
File:Gestalt closure.svg

The principles of grouping (or Gestalt laws of grouping) are a set of principles in psychology, first proposed by Gestalt psychologists to explain how humans naturally perceive objects as organized patterns and objects. Gestalt psychologists argued that these principles exist because the mind has an innate disposition to perceive patterns in the stimulus based on certain rules. These principles are organized into six categories. The principle of proximity states that, all else being equal, perception tends to group stimuli that are close together as part of the same object, and stimuli that are far apart as two separate objects. The principle of similarity states that, all else being equal, perception lends itself to seeing stimuli that physically resemble each other as part of the same object, and stimuli that are different as part of a different object. This allows for people to distinguish between adjacent and overlapping objects based on their visual texture and resemblance. The principle of closure refers to the mind’s tendency to see complete figures or forms even if a picture is incomplete, partially hidden by other objects, or if part of the information needed to make a complete picture in our minds is missing. For example, if part of a shape’s border is missing people still tend to see the shape as completely enclosed by the border and ignore the gaps. The principle of good continuation makes sense of stimuli that overlap: when there is an intersection between two or more objects, people tend to perceive each as a single uninterrupted object. The principle of common fate groups stimuli together on the basis of their movement. When visual elements are seen moving in the same direction at the same rate, perception associates the movement as part of the same stimulus. This allows people to make out moving objects even when other details, such as color or outline, are obscured. The principle of good form refers to the tendency to group together forms of similar shape, pattern, color, etc.[20][21][22][23] Later research has identified additional grouping principles.[24]

Contrast effects

Main article: Contrast effect

A common finding across many different kinds of perception is that the perceived qualities of an object can be affected by the qualities of context. If one object is extreme on some dimension, then neighboring objects are perceived as further away from that extreme. "Simultaneous contrast effect" is the term used when stimuli are presented at the same time, whereas "successive contrast" applies when stimuli are presented one after another.[25]

The contrast effect was noted by the 17th Century philosopher John Locke, who observed that lukewarm water can feel hot or cold, depending on whether the hand touching it was previously in hot or cold water.[26] In the early 20th Century, Wilhelm Wundt identified contrast as a fundamental principle of perception, and since then the effect has been confirmed in many different areas.[26] These effects shape not only visual qualities like color and brightness, but other kinds of perception, including how heavy an object feels.[27] One experiment found that thinking of the name "Hitler" led to subjects rating a person as more hostile.[28] Whether a piece of music is perceived as good or bad can depend on whether the music heard before it was unpleasant or pleasant.[29] For the effect to work, the objects being compared need to be similar to each other: a television reporter can seem smaller when interviewing a tall basketball player, but not when standing next to a tall building.[27]

Effect of experience

Main article: Perceptual learning

With experience, organisms can learn to make finer perceptual distinctions, and learn new kinds of categorization. Wine-tasting, the reading of X-ray images and music appreciation are applications of this process in the human sphere. Research has focused on the relation of this to other kinds of learning, and whether it takes place in peripheral sensory systems or in the brain's processing of sense information. [citation needed]

Effect of motivation and expectation

Main article: Set (psychology)

A perceptual set, also called perceptual expectancy or just set is a predisposition to perceive things in a certain way.[30] It is an example of how perception can be shaped by "top-down" processes such as drives and expectations.[31] Perceptual sets occur in all the different senses.[16] They can be long term, such as a special sensitivity to hearing one's own name in a crowded room, or short term, as in the ease with which hungry people notice the smell of food.[32] A simple demonstration of the effect involved very brief presentations of non-words such as "sael". Subjects who were told to expect words about animals read it as "seal", but others who were expecting boat-related words read it as "sail".[32]

Sets can be created by motivation and so can result in people interpreting ambiguous figures so that they see what they want to see.[31] For instance, how someone perceives what unfolds during a sports game can be biased if they strongly support one of the teams.[33] In one experiment, students were allocated to pleasant or unpleasant tasks by a computer. They were told that either a number or a letter would flash on the screen to say whether they were going to taste an orange juice drink or an unpleasant-tasting health drink. In fact, an ambiguous figure was flashed on screen, which could either be read as the letter B or the number 13. When the letters were associated with the pleasant task, subjects were more likely to perceive a letter B, and when letters were associated with the unpleasant task they tended to perceive a number 13.[30]

Perceptual set has been demonstrated in many social contexts. People who are primed to think of someone as "warm" are more likely to perceive a variety of positive characteristics in them, than if the word "warm" is replaced by "cold". When someone has a reputation for being funny, an audience are more likely to find them amusing.[32] Individual's perceptual sets reflect their own personality traits. For example, people with an aggressive personality are quicker to correctly identify aggressive words or situations.[32]

One classic psychological experiment showed slower reaction times and less accurate answers when a deck of playing cards reversed the color of the suit symbol for some cards (e.g. red spades and black hearts).[34]

Philosopher Andy Clark explains that perception, although it occurs quickly, is not simply a bottom-up process (where minute details are put together to form larger wholes). Instead, our brains use what he calls Predictive coding. It starts with very broad constraints and expectations for the state of the world, and as expectations are met, it makes more detailed predictions (errors lead to new predictions, or learning processes). Clark says this research has various implications; not only can there be no completely "unbiased, unfiltered" perception, but this means that there is a great deal of feedback between perception and expectation (perceptual experiences often shape our beliefs, but those perceptions were based on existing beliefs).[35]

Theories

Perception as direct perception

Cognitive theories of perception assume there is a poverty of stimulus. This (with reference to perception) is the claim that sensations are, by themselves, unable to provide a unique description of the world. "[36] Sensations require 'enriching', which is the role of the mental model. A different type of theory is the perceptual ecology approach of James J. Gibson. Gibson rejected the assumption of a poverty of stimulus by rejecting the notion that perception is based upon sensations – instead, he investigated what information is actually presented to the perceptual systems. His theory "assumes the existence of stable, unbounded, and permanent stimulus-information in the ambient optic array. And it supposes that the visual system can explore and detect this information. The theory is information-based, not sensation-based."[37] He and the psychologists who work within this paradigm detailed how the world could be specified to a mobile, exploring organism via the lawful projection of information about the world into energy arrays.[38] Specification is a 1:1 mapping of some aspect of the world into a perceptual array; given such a mapping, no enrichment is required and perception is direct perception.[39]

Perception-in-action

An ecological understanding of perception derived from Gibson's early work is that of "perception-in-action", the notion that perception is a requisite property of animate action; that without perception action would be unguided, and without action perception would serve no purpose. Animate actions require both perception and motion, and perception and movement can be described as "two sides of the same coin, the coin is action". Gibson works from the assumption that singular entities, which he calls "invariants", already exist in the real world and that all that the perception process does is to home in upon them. A view known as constructivism (held by such philosophers as Ernst von Glasersfeld) regards the continual adjustment of perception and action to the external input as precisely what constitutes the "entity", which is therefore far from being invariant.[40]

Glasersfeld considers an "invariant" as a target to be homed in upon, and a pragmatic necessity to allow an initial measure of understanding to be established prior to the updating that a statement aims to achieve. The invariant does not and need not represent an actuality, and Glasersfeld describes it as extremely unlikely that what is desired or feared by an organism will never suffer change as time goes on. This social constructionist theory thus allows for a needful evolutionary adjustment.[41]

A mathematical theory of perception-in-action has been devised and investigated in many forms of controlled movement, and has been described in many different species of organism using the General Tau Theory. According to this theory, tau information, or time-to-goal information is the fundamental 'percept' in perception.

Evolutionary psychology and perception

Many philosophers, such as Jerry Fodor, write that the purpose of perception is knowledge, but evolutionary psychologists hold that its primary purpose is to guide action.[42] For example, they say, depth perception seems to have evolved not to help us know the distances to other objects but rather to help us move around in space.[42] Evolutionary psychologists say that animals from fiddler crabs to humans use eyesight for collision avoidance, suggesting that vision is basically for directing action, not providing knowledge.[42]

Building and maintaining sense organs is metabolically expensive, so these organs evolve only when they improve an organism's fitness.[42] More than half the brain is devoted to processing sensory information, and the brain itself consumes roughly one-fourth of one's metabolic resources, so the senses must provide exceptional benefits to fitness.[42] Perception accurately mirrors the world; animals get useful, accurate information through their senses.[42]

Scientists who study perception and sensation have long understood the human senses as adaptations.[42] Depth perception consists of processing over half a dozen visual cues, each of which is based on a regularity of the physical world.[42] Vision evolved to respond to the narrow range of electromagnetic energy that is plentiful and that does not pass through objects.[42] Sound waves provide useful information about the sources of and distances to objects, with larger animals making and hearing lower-frequency sounds and smaller animals making and hearing higher-frequency sounds.[42] Taste and smell respond to chemicals in the environment that were significant for fitness in the EEA.[42] The sense of touch is actually many senses, including pressure, heat, cold, tickle, and pain.[42] Pain, while unpleasant, is adaptive.[42] An important adaptation for senses is range shifting, by which the organism becomes temporarily more or less sensitive to sensation.[42] For example, one's eyes automatically adjust to dim or bright ambient light.[42] Sensory abilities of different organisms often coevolve, as is the case with the hearing of echolocating bats and that of the moths that have evolved to respond to the sounds that the bats make.[42]

Evolutionary psychologists claim that perception demonstrates the principle of modularity, with specialized mechanisms handling particular perception tasks.[42] For example, people with damage to a particular part of the brain suffer from the specific defect of not being able to recognize faces (prospagnosia).[42] EP suggests that this indicates a so-called face-reading module.[42]

Theories of visual perception

Physiology

Main article: Sensory system

A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic sensation (touch), taste and olfaction (smell). It has been suggested that the immune system is an overlooked sensory modlality.[43] In short, senses are transducers from the physical world to the realm of the mind.

The receptive field is the specific part of the world to which a receptor organ and receptor cells respond. For instance, the part of the world an eye can see, is its receptive field; the light that each rod or cone can see, is its receptive field.[44] Receptive fields have been identified for the visual system, auditory system and somatosensory system, so far.

Types

Of sound

File:Anatomy of the Human Ear.svg
Main article: Hearing (sense)

Hearing (or audition) is the ability to perceive sound by detecting vibrations. Frequencies capable of being heard by humans are called audio or sonic. The range is typically considered to be between 20 Hz and 20,000 Hz.[45] Frequencies higher than audio are referred to as ultrasonic, while frequencies below audio are referred to as infrasonic. The auditory system includes the ears and inner structures which produce neural signals in response to the sound. The primary auditory cortex, within the temporal lobe of the human brain, is where auditory information arrives in the cerebral cortex.

Sound does not usually come from a single source: in real situations, sounds from multiple sources and directions are superimposed as they arrive at the ears. Hearing involves the computationally complex task of separating out the sources of interest, often estimating their distance and direction as well as identifying them.[15]

Of speech

Main article: Speech perception
File:Spectrogram of I owe you.png

Speech perception is the process by which the sounds of language are heard, interpreted and understood. Research in speech perception seeks to understand how human listeners recognize speech sounds and use this information to understand spoken language. The sound of a word can vary widely according to words around it and the tempo of the speech, as well as the physical characteristics, accent and mood of the speaker. Listeners manage to perceive words across this wide range of different conditions.[citation needed] Another variation is that reverberation can make a large difference in sound between a word spoken from the far side of a room and the same word spoken up close. Experiments have shown that people automatically compensate for this effect when hearing speech.[15][46]

The process of perceiving speech begins at the level of the sound within the auditory signal and the process of audition. After processing the initial auditory signal, speech sounds are further processed to extract acoustic cues and phonetic information. This speech information can then be used for higher-level language processes, such as word recognition. Speech perception is not necessarily uni-directional. That is, higher-level language processes connected with morphology, syntax, or semantics may interact with basic speech perception processes to aid in recognition of speech sounds.[citation needed] It may be the case that it is not necessary and maybe even not possible for a listener to recognize phonemes before recognizing higher units, like words for example. In one experiment, Richard M. Warren replaced one phoneme of a word with a cough-like sound. His subjects restored the missing speech sound perceptually without any difficulty and what is more, they were not able to identify accurately which phoneme had been disturbed.[47]

Touch

Main article: Haptic perception

Haptic perception is the process of recognizing objects through touch. It involves a combination of somatosensory perception of patterns on the skin surface (e.g., edges, curvature, and texture) and proprioception of hand position and conformation. People can rapidly and accurately identify three-dimensional objects by touch.[48] This involves exploratory procedures, such as moving the fingers over the outer surface of the object or holding the entire object in the hand.[49] Haptic perception relies on the forces experienced during touch.[50]

Gibson defined the haptic system as "The sensibility of the individual to the world adjacent to his body by use of his body".[51] Gibson and others emphasized the close link between haptic perception and body movement: haptic perception is active exploration. The concept of haptic perception is related to the concept of extended physiological proprioception according to which, when using a tool such as a stick, perceptual experience is transparently transferred to the end of the tool.

Taste

Main article: Taste

Taste (or, the more formal term, gustation) is the ability to perceive the flavor of substances including, but not limited to, food. Humans receive tastes through sensory organs called taste buds, or gustatory calyculi, concentrated on the upper surface of the tongue.[52] The human tongue has 100 to 150 taste receptor cells on each of its roughly ten thousand taste buds.[53] There are five primary tastes: sweetness, bitterness, sourness, saltiness, and umami. Other tastes can be mimicked by combining these basic tastes.[53][54] The recognition and awareness of umami is a relatively recent development in Western cuisine.[55] The basic tastes contribute only partially to the sensation and flavor of food in the mouth — other factors include smell, detected by the olfactory epithelium of the nose;[5] texture, detected through a variety of mechanoreceptors, muscle nerves, etc.;[54][56] and temperature, detected by thermoreceptors.[54] All basic tastes are classified as either appetitive or aversive, depending upon whether the things they sense are harmful or beneficial.[57]

Other senses

Main article: Sense

Other senses enable perception of body balance, acceleration, gravity, position of body parts, temperature, pain, time, and perception of internal senses such as suffocation, gag reflex, intestinal distension, fullness of rectum and urinary bladder, and sensations felt in the throat and lungs.

Of the social world

Main article: Social perception

Social perception is the part of perception that allows people to understand the individuals and groups of their social world, and thus an element of social cognition.[58]

Types of sensory perception

Other types of perception

See also

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Notes

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  37. Gibson, James J. (2002): "A Theory of Direct Visual Perception". In: Alva Noë/Evan Thompson (Eds.), Vision and Mind. Selected Readings in the Philosophy of Perception, Cambridge, MIT Press, pp. 77–89.
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  39. Richards, Robert J. (December 1976). James Gibson's Passive Theory of Perception: A Rejection of the Doctrine of Specific Nerve Energies. Philosophy and Phenomenological Research 37 (2): 218–233.
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