Understanding the Brain


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Perception (from the Latin perceptio, percipio) is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information.[1][2] All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs.[3] 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.[4][5] Perception involves these "top-down" effects as well as the "bottom-up" process of processing sensory input.[5] Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness.[3]




Process and terminology

The process of perception begins with an object in the real world, termed the distal stimulus or distal object.[citation needed] 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.[1][3] This raw pattern of neural activity is called the proximal stimulus.[citation needed] These neural signals are transmitted to the brain and processed.[3] The resulting mental recreation 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.



Perception and reality

In the case of visual perception, some people can actually see the percept shift in their mind's eye.[11] 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.






Perceptual constancy is the ability of perceptual systems to recognise the same object from widely varying sensory inputs.[5][13] 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.[14] 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.[15][16] 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.[16] 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.[16] Other constancies include melody, odor, brightness and words.[17] These constancies are not always total, but the variation in the percept is much less than the variation in the physical stimulus.[16] The perceptual systems of the brain achieve perceptual constancy in a variety of ways, each specialized for the kind of information being processed.[18]


Law of Closure


Contrast effects

Two physically identical orange squares are perceived as different subjective colors, because each has a different surrounding color.[24]



Effect of experience


Effect of motivation and expectation







Perception as hypothesis-testing






Evolutionary psychology and perception

Many experts, such as Jerry Fodor, write that the purpose of perception is knowledge, but evolutionary psychologists hold that its primary purpose is to guide action.[39] 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.[39] 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.[39]

Building and maintaining sense organs is metabolically expensive, so these organs evolve only when they improve an organism's fitness.[39] 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.[39] Perception accurately mirrors the world; animals get useful, accurate information through their senses.[39]

Scientists who study perception and sensation have long understood the human senses as adaptations.[39] Depth perception consists of processing over half a dozen visual cues, each of which is based on a regularity of the physical world.[39] Vision evolved to respond to the narrow range of electromagnetic energy that is plentiful and that does not pass through objects.[39] 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.[39] Taste and smell respond to chemicals in the environment that were significant for fitness in the EEA.[39] The sense of touch is actually many senses, including pressure, heat, cold, tickle, and pain.[39] Pain, while unpleasant, is adaptive.[39] An important adaptation for senses is range shifting, by which the organism becomes temporarily more or less sensitive to sensation.[39] For example, one's eyes automatically adjust to dim or bright ambient light.[39] 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.[39]

Evolutionary psychologists claim that perception demonstrates the principle of modularity, with specialized mechanisms handling particular perception tasks.[39] 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).[39] EP suggests that this indicates a so-called face-reading module.[39]

Theories of visual perception



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.[40] Receptive fields have been identified for the visual system, auditory system and somatosensory system, so far.


Of sound




Of speech





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.[44] This involves exploratory procedures, such as moving the fingers over the outer surface of the object or holding the entire object in the hand.[45] Haptic perception relies on the forces experienced during touch.[46]



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.[48] The human tongue has 100 to 150 taste receptor cells on each of its roughly ten thousand taste buds.[49] There are five primary tastes: sweetness, bitterness, sourness, saltiness, and umami. Other tastes can be mimicked by combining these basic tastes.[49][50] The recognition and awareness of umami is a relatively recent development in Western cuisine.[51] 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;[6] texture, detected through a variety of mechanoreceptors, muscle nerves, etc.;[50][52] and temperature, detected by thermoreceptors.[50] All basic tastes are classified as either appetitive or aversive, depending upon whether the things they sense are harmful or beneficial.[53]

Of the social world


See also


  2. Defined as "receiving, collecting, action of taking possession, apprehension with the mind or senses." in Oxford English Dictionary: The definitive record of the English language
  3. 3.0 3.1 3.2 3.3 Goldstein (2009) pp. 5–7
  4. 4.0 4.1 4.2 4.3 4.4 Gregory, Richard. "Perception" in Gregory, Zangwill (1987) pp. 598–601
  5. 5.0 5.1 5.2 Bernstein, Douglas A. (5 March 2010). Essentials of Psychology. Cengage Learning. pp. 123–124. ISBN 9780495906933. http://books.google.com/books?id=rd77N0KsLVkC&pg=PA123. Retrieved 25 March 2011. 
  6. 6.0 6.1 DeVere, Ronald; Calvert, Marjorie (31 August 2010). Navigating Smell and Taste Disorders. Demos Medical Publishing. pp. 33–37. ISBN 9781932603965. http://books.google.com/books?id=m6WOtX2QAtwC&pg=PA39. Retrieved 26 March 2011. 
  7. http://www.learner.org/discoveringpsychology/07/e07glossary.html
  8. Willis, William D.; Coggeshall, Richard E. (31 January 2004). Sensory Mechanisms of the Spinal Cord: Primary afferent neurons and the spinal dorsal horn. Springer. p. 1. ISBN 9780306480331. http://books.google.com/books?id=uqnKCewO2voC&pg=PA1. Retrieved 25 March 2011. 
  9. Leibniz' Monadology
  10. Deleuze and Guattari's What is Philosophy?
  13. Atkinson, Rita L.; Atkinson, Richard C.; Smith, Edward E. (March 1990). Introduction to psychology. Harcourt Brace Jovanovich. pp. 177–183. ISBN 9780155436893. http://books.google.com/books?id=Nw54PwAACAAJ. Retrieved 24 March 2011. 
  14. 14.0 14.1 14.2 Moore, Brian C. J. (15 October 2009). "Audition". In Goldstein, E. Bruce. Encyclopedia of Perception. Sage. pp. 136–137. ISBN 9781412940818. http://books.google.com/books?id=Y4TOEN4f5ZMC&pg=PA136. Retrieved 26 March 2011. 
  15. 15.0 15.1 Sonderegger, Theo (16 October 1998). Psychology. John Wiley and Sons. pp. 45–46. ISBN 9780822053279. http://books.google.com/books?id=UUrCHiSb_QsC&pg=PA45. Retrieved 24 March 2011. 
  16. 16.0 16.1 16.2 16.3 Goldstein, E. Bruce (15 October 2009). "Constancy". In E. Bruce Goldstein. Encyclopedia of Perception. Sage. pp. 309–313. ISBN 9781412940818. http://books.google.com/books?id=Y4TOEN4f5ZMC&pg=PA309. Retrieved 26 March 2011. 
  17. Roeckelein, Jon E. (2006). Elsevier's dictionary of psychological theories. Elsevier. p. 126. ISBN 9780444517500. http://books.google.com/books?id=1Yn6NZgxvssC&pg=PA126. Retrieved 24 March 2011. 
  18. Yantis, Steven (2001). Visual perception: essential readings. Psychology Press. p. 7. ISBN 9780863775987. http://books.google.com/books?id=GpGvYSTk9gYC&pg=PA7. Retrieved 24 March 2011. 
  20. Wolfe, Jeremy M.; Kluender, Keith R.; Levi, Dennis M.; Bartoshuk, Linda M.; Herz, Rachel S.; Klatzky, Roberta L.; Lederman, Susan J. (2008). "Gestalt Grouping Principles". Sensation and Perception (2nd ed.). Sinauer Associates. pp. 78, 80. ISBN 9780878939381. http://www.sinauer.com./wolfe/chap4/gestaltF.htm. 
  21. Goldstein (2009). pp. 105–107
  23. Weiten, Wayne (1998). Psychology: themes and variations (4th ed.). Brooks/Cole Pub. Co.. p. 144. ISBN 9780534340148. 
  24. Dale Purves and R. Beau Lotto, 2003. Why we see what we do: an empirical theory of vision. Sinaeur Associates
  25. Corsini, Raymond J. (2002). The dictionary of psychology. Psychology Press. p. 219. ISBN 9781583913284. http://books.google.com/books?id=0uxnglHzYaoC&pg=PA219. Retrieved 24 March 2011. 
  26. 26.0 26.1 Kushner, Laura H. (2008). Contrast in judgments of mental health. ProQuest. p. 1. ISBN 9780549913146. http://books.google.com/books?id=TYn5VHp9jioC&pg=PA1. Retrieved 24 March 2011. 
  27. 27.0 27.1 Plous, Scott (1993). The psychology of judgment and decision making. McGraw-Hill. pp. 38–41. ISBN 9780070504776. http://books.google.com/books?id=xvWOQgAACAAJ. Retrieved 24 March 2011. 
  28. Moskowitz, Gordon B. (2005). Social cognition: understanding self and others. Guilford Press. p. 421. ISBN 9781593850852. http://books.google.com/books?id=_-NLW8Ynvp8C&pg=PA421. Retrieved 24 March 2011. 
  29. Popper, Arthur N. (30 November 2010). Music Perception. Springer. p. 150. ISBN 9781441961136. http://books.google.com/books?id=ZYXd3CF1_vkC&pg=PA150. Retrieved 24 March 2011. 
  30. 30.0 30.1 Weiten, Wayne (17 December 2008). Psychology: Themes and Variations. Cengage Learning. p. 193. ISBN 9780495601975. http://books.google.com/books?id=sILajOhJpOsC&pg=PT193. Retrieved 24 March 2011. 
  31. 31.0 31.1 Coon, Dennis; Mitterer, John O. (29 December 2008). Introduction to Psychology: Gateways to Mind and Behavior. Cengage Learning. pp. 171–172. ISBN 9780495599111. http://books.google.com/books?id=vw20LEaJe10C&pg=PA171. Retrieved 24 March 2011. 
  32. 32.0 32.1 32.2 32.3 Hardy, Malcolm; Heyes, Steve (2 December 1999). Beginning Psychology. Oxford University Press. pp. 24–27. ISBN 9780198328216. http://books.google.com/books?id=fjPWqXi9WQsC&pg=PA24. Retrieved 24 March 2011. 
  33. Block, J. R.; Yuker, Harold E. (1 October 2002). Can You Believe Your Eyes?: Over 250 Illusions and Other Visual Oddities. Robson. pp. 173–174. ISBN 9781861055866. http://books.google.com/books?id=uNMFiMQu8BMC&pg=PA173. Retrieved 24 March 2011. 
  35. http://www.edge.org/q2011/q11_6.html
  39. 39.00 39.01 39.02 39.03 39.04 39.05 39.06 39.07 39.08 39.09 39.10 39.11 39.12 39.13 39.14 39.15 39.16 39.17 39.18 Gaulin, Steven J. C. and Donald H. McBurney. Evolutionary Psychology. Prentice Hall. 2003. ISBN 13: 9780131115293, Chapter 4, p 81-101.
  40. Kolb & Whishaw: Fundamentals of Human Neuropsychology (2003)
  41. "Frequency Range of Human Hearing". The Physics Factbook. http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml. 
  42. Watkins, Anthony J.; Raimond, Andrew; Makin, Simon J. (23 March 2010). "Room reflection and constancy in speech-like sounds: Within-band effects". In Enrique A. Lopez-Poveda. The Neurophysiological Bases of Auditory Perception. Springer. p. 440. ISBN 9781441956859. http://books.google.com/books?id=ACkNL-G7gUUC&pg=PA440. Retrieved 26 March 2011. 
  44. Klatzky RL, Lederman SJ, & Metzger VA (1985). "Identifying objects by touch: An "expert system."". Perception & Psychophysics (37): 299–302. 
  45. Lederman SJ, & Klatzky RL (1987). "Hand movements: A window into haptic object recognition". Cognitive Psychology (19): 342–368. 
  47. Gibson, J.J. (1966). The senses considered as perceptual systems.. Boston: Houghton Mifflin. ISBN 0313239614. 
  49. 49.0 49.1 DeVere, Ronald; Calvert, Marjorie (31 August 2010). Navigating Smell and Taste Disorders. Demos Medical Publishing. pp. 39–40. ISBN 9781932603965. http://books.google.com/books?id=m6WOtX2QAtwC&pg=PA39. Retrieved 26 March 2011. 
  50. 50.0 50.1 50.2 Siegel, George J.; Albers, R. Wayne (2006). Basic neurochemistry: molecular, cellular, and medical aspects. Academic Press. p. 825. ISBN 9780120883974. http://books.google.com/books?id=Af0IyHtGCMUC&pg=PA825. Retrieved 26 March 2011. 



Further reading

External links