Perception - AbsoluteAstronomy.com

Perception is the process of attaining awareness

Awareness

Awareness is the state or ability to perceive, to feel, or to be conscious of events, objects or sensory patterns. In this level of consciousness, sense data can be confirmed by an observer without necessarily implying understanding. More broadly, it is the state or quality of being aware of...

or understanding

Understanding

Understanding is a psychological process related to an abstract or physical object, such as a person, situation, or message whereby one is able to think about it and use concepts to deal adequately with that object....

of the environment

Natural environment

The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....

by organizing and interpreting sensory

Sense

Senses are physiological capacities of organisms that provide inputs for perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception...

information

Information

Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...

. All perception involves signals in the nervous system

Nervous system

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...

, which in turn result from physical stimulation of the sense organs. For example, vision involves light

Photon

In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...

striking the retina

Retina

The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

s 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

Perceptual learning

The term perceptual learning refers to the process of long lasting improvement in performing perceptual tasks as a function of experienceand practice . According to Eleanor Gibson , it refers to the experience-induced changes in the way information is extracted following sensory experience...

, memory

Memory

In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

and expectation. Perception involves these "top-down" effects as well as the "bottom-up" process of processing sensory input. Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness.

Since the rise of experimental psychology

Experimental psychology

Experimental psychology is a methodological approach, rather than a subject, and encompasses varied fields within psychology. Experimental psychologists have traditionally conducted research, published articles, and taught classes on neuroscience, developmental psychology, sensation, perception,...

in the late 19th Century, psychology's understanding of perception

Perceptual psychology

Perceptual psychology is a subfield of cognitive psychology that is concerned specifically with the pre-conscious innate aspects of the human cognitive system: perception....

has progressed by combining a variety of techniques. Psychophysics

Psychophysics

Psychophysics quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they effect. Psychophysics has been described as "the scientific study of the relation between stimulus and sensation" or, more completely, as "the analysis of perceptual...

measures the effect on perception of varying the physical qualities of the input. Sensory neuroscience

Sensory neuroscience

Sensory neuroscience is a subfield of neuroscience which explores the anatomy and physiology of neurons that are part of sensory systems such as vision, hearing, and olfaction. Neurons in sensory regions of the brain respond to stimuli by firing one or more nerve impulses following stimulus...

studies the brain mechanisms underlying perception. Perceptual systems can also be studied computation

Computation

Computation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc...

ally, in terms of the information they process. Perceptual issues in philosophy

Philosophy of perception

The philosophy of perception is concerned with the nature of perceptual experience and the status of perceptual data, in particular how they relate to beliefs about, or knowledge of, the world. Any explicit account of perception requires a commitment to one of a variety of ontological or...

include the extent to which sensory qualities such as sounds, smells or colors exist in objective reality rather than the mind of the perceiver.

Although the senses were traditionally viewed as passive receptors, the study of illusion

Illusion

An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people....

s and ambiguous image

Ambiguous image

Ambiguous images are optical illusion images which are crafted to exploit graphical similarities and other properties of visual system interpretation between two or more distinct image forms...

s has demonstrated that the brain's perceptual systems actively and pre-consciously attempt to make sense of their input. There is still active debate about the extent to which perception is an active process of hypothesis

Hypothesis

A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

testing, analogous to science

Science

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...

, or whether realistic sensory information is rich enough to make this process unnecessary.

The perceptual system

Perceptual system

A perceptual system is a computational system designed to make inferences about properties of a physical environment based on scenes. Other definitions may exist....

s of the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

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

Cognitive module

A cognitive module is, in theories of the modularity of mind and the closely related society of mind theory, a specialised tool or sub-unit that can be used by other parts to resolve cognitive tasks. The question of their existence and nature is a major topic in cognitive science and evolutionary...

, with different areas processing different kinds of sensory information. Some of these modules take the form of sensory maps

Sensory Maps

Sensory Maps are areas of the brain which respond to sensory stimulation, and are spatially organized according to some feature of the sensory stimulation. In some cases the sensory map is simply a topographic representation of a sensory surface such as the skin, cochlea, or retina...

, 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.

Process and terminology

The process of perception begins with an object in the real world, termed the distal stimulus or distal object. 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. This raw pattern of neural activity is called the proximal stimulus. These neural signals are transmitted to the brain and processed. The resulting mental recreation of the distal stimulus is the percept. Perception is sometimes described as the process of constructing mental representation

Mental representation

A representation, in philosophy of mind, cognitive psychology, neuroscience, and cognitive science, is a hypothetical internal cognitive symbol that represents external reality, or else a mental process that makes use of such a symbol; "a formal system for making explicit certain entities or types...

s 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. 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

Stimulus modality

Stimulus modality also sensory modality is one aspect of a stimulus or what we percieve after a stimulus. For example the temperature modality is registered after heat or cold stimulate a receptor. There are many modalities: temperature, taste, pressure...

".

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

Multistable perception

Multistable perceptual phenomena are a form of perceptual phenomena in which there are unpredictable sequences of spontaneous subjective changes...

". 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

Rubin vase

Rubin's vase is a famous set of ambiguous or bi-stable two-dimensional forms developed around 1915 by the Danish psychologist Edgar Rubin...

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, Bergson, Deleuze and Guattari 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

Mind's eye

The phrase "mind's eye" refers to the human ability for visualization, i.e., for the experiencing of visual mental imagery; in other words, one's ability to "see" things with the mind.- Physical basis :...

. 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

Ambiguous image

Ambiguous images are optical illusion images which are crafted to exploit graphical similarities and other properties of visual system interpretation between two or more distinct image forms...

has multiple interpretations on the perceptual level.

This confusing ambiguity of perception is exploited in human technologies such as camouflage

Camouflage

Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...

, 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.

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

Gestalt psychology

Gestalt psychology or gestaltism is a theory of mind and brain of the Berlin School; the operational principle of gestalt psychology is that the brain is holistic, parallel, and analog, with self-organizing tendencies...

school of psychology, with its emphasis on holistic

Holism

Holism is the idea that all the properties of a given system cannot be determined or explained by its component parts alone...

approach.

Constancy

Perceptual constancy is the ability of perceptual systems to recognise the same object from widely varying sensory inputs. 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. 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. One kind of perceptual constancy is color constancy
Color constancy
Color constancy is an example of subjective constancy and a feature of the human color perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. A green apple for instance looks green to us at midday, when the main...

: for example, a white piece of paper can be recognised as such under different colors and intensities of light. 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. Other constancies include melody, odor, brightness and words. These constancies are not always total, but the variation in the percept is much less than the variation in the physical stimulus. The perceptual systems of the brain achieve perceptual constancy in a variety of ways, each specialized for the kind of information being processed.

Grouping

The principles of grouping (or Gestalt laws of grouping) are a set of principles in psychology

Psychology

Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

, first proposed by Gestalt psychologists

Gestalt psychology

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 five 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. Later research has identified additional grouping principles.

Contrast effects

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.

The contrast effect was noted by the 17th Century philosopher John Locke

John Locke

John Locke FRS , widely known as the Father of Liberalism, was an English philosopher and physician regarded as one of the most influential of Enlightenment thinkers. Considered one of the first of the British empiricists, following the tradition of Francis Bacon, he is equally important to social...

, who observed that lukewarm water can feel hot or cold, depending on whether the hand touching it was previously in hot or cold water. In the early 20th Century, Wilhelm Wundt

Wilhelm Wundt

Wilhelm Maximilian Wundt was a German physician, psychologist, physiologist, philosopher, and professor, known today as one of the founding figures of modern psychology. He is widely regarded as the "father of experimental psychology"...

identified contrast as a fundamental principle of perception, and since then the effect has been confirmed in many different areas. These effects shape not only visual qualities like color and brightness, but other kinds of perception, including how heavy an object feels. One experiment found that thinking of the name "Hitler" led to subjects rating a person as more hostile. Whether a piece of music is perceived as good or bad can depend on whether the music heard before it was unpleasant or pleasant. 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.

Effect of experience

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.

Effect of motivation and expectation

A perceptual set, also called perceptual expectancy or just set is a predisposition to perceive things in a certain way. It is an example of how perception can be shaped by "top-down" processes such as drives and expectations. Perceptual sets occur in all the different senses. 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. 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".

Sets can be created by motivation

Motivation

Motivation is the driving force by which humans achieve their goals. Motivation is said to be intrinsic or extrinsic. The term is generally used for humans but it can also be used to describe the causes for animal behavior as well. This article refers to human motivation...

and so can result in people interpreting ambiguous figures so that they see what they want to see. For instance, how someone perceives what unfolds during a sports game can be biased if they strongly support one of the teams. 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.

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. 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.

One classic psychological experiment showed slower reaction times and less accurate answers when a deck of playing cards reversed the color of the suit

Suit (cards)

In playing cards, a suit is one of several categories into which the cards of a deck are divided. Most often, each card bears one of several symbols showing to which suit it belongs; the suit may alternatively or in addition be indicated by the color printed on the card...

symbol for some cards (e.g. red spades and black hearts).

Philosopher Andy Clark

Andy Clark

Andy Clark is a Professor of Philosophy and Chair in Logic and Metaphysics at the University of Edinburgh in Scotland. Before this he was director of the Cognitive Science Program at Indiana University in Bloomington. Previously, he taught at Washington University at St. Louis and the University...

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

Learning

Learning is acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human 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).

Perception as hypothesis-testing

Cognitive theories

Cognition

In science, cognition refers to mental processes. These processes include attention, remembering, producing and understanding language, solving problems, and making decisions. Cognition is studied in various disciplines such as psychology, philosophy, linguistics, and computer science...

of perception assume there is a poverty of stimulus

Stimulus (physiology)

In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....

. This (with reference to perception) is the claim that sensations are, by themselves, unable to provide a unique description of the world. Sensations require 'enriching', which is the role of the mental model. A different type of theory is the perceptual ecology

Ecology

Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

approach of 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. 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." He and the psychologists who work within this paradigm

Paradigm

The word paradigm has been used in science to describe distinct concepts. It comes from Greek "παράδειγμα" , "pattern, example, sample" from the verb "παραδείκνυμι" , "exhibit, represent, expose" and that from "παρά" , "beside, beyond" + "δείκνυμι" , "to show, to point out".The original Greek...

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.

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

Constructivism

Constructivism may refer to:* Constructivist epistemology, the philosophical view* Constructivism in international relations* Constructivism , a philosophical view on mathematical proofs and existence of mathematical objects...

(held by such philosophers as Ernst von Glasersfeld

Ernst von Glasersfeld

Ernst von Glasersfeld was a philosopher, and Emeritus Professor of Psychology at the University of Georgia, Research Associate at the Scientific Reasoning Research Institute, and Adjunct Professor in the Department of Psychology at the University of Massachusetts, Amherst...

) 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.

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.

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

General Tau Theory

General tau theory deals with the guidance of bodily movements. All movements of the body, and within the body, require guided closure of action-gaps. An action-gap, generally defined, is the changing gap between a current state and a goal state...

. According to this theory, tau information, or time-to-goal information is the fundamental 'percept' in perception.

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. 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. 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.

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

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

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

Theories of visual perception

Empirical theories of perception
Empirical theories of perception
An empirical theory of perception is a kind of explanation for how percepts arise. These theories hold that sensory systems incorporate information about the statistical properties of the natural world into their design and relate incoming stimuli to this information, rather than analyzing sensory...
Anne Treisman's Feature Integration Theory
Feature integration theory
The feature integration theory, developed by Anne Treisman and Garry Gelade since the early 1980s, posits that different kinds of attention are responsible for binding different features into consciously experienced wholes...
Interactive Activation and Competition
Interactive Activation and Competition
Interactive Activation and Competition networks are neural networks used to model memory and intuitive generalizations. They are made up of nodes or artificial neurons which are arrayed and activated in ways that emulate the behaviors of human memory....
Irving Biederman's Recognition by Components Theory
Recognition by Components Theory
The Recognition-by-components theory, or RBC theory, is a bottom-up process proposed by Irving Biederman to explain object recognition. According to RBC theory, we are able to recognize objects by separating them into geons...

Physiology

A sensory system is a part of the nervous system

Nervous system

responsible for processing sensory

Sense

information. A sensory system consists of sensory receptor

Sensory receptor

In a sensory system, a sensory receptor is a sensory nerve ending that responds to a stimulus in the internal or external environment of an organism...

s, neural pathway

Neural pathway

A neural pathway, neural tract, or neural face, connects one part of the nervous system with another and usually consists of bundles of elongated, myelin-insulated neurons, known collectively as white matter...

s, and parts of the brain

Brain

involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing

Hearing (sense)

Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...

, somatic sensation (touch), taste

Taste

Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....

and olfaction

Olfaction

Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...

(smell). In short, senses are transducers from the physical world to the realm of the mind.

The receptive field

Receptive field

The receptive field of a sensory neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron. Receptive fields have been identified for neurons of the auditory system, the somatosensory system, and the visual system....

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

Rod cell

Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than can the other type of visual photoreceptor, cone cells. Named for their cylindrical shape, rods are concentrated at the outer edges of the retina and are used in peripheral vision. On...

or cone

Cone cell

Cone cells, or cones, are photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. If the retina is exposed to an intense visual stimulus, a negative afterimage will be...

can see, is its receptive field. Receptive field

Receptive field

s have been identified for the visual system

Visual system

The visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...

, auditory system

Auditory system

The auditory system is the sensory system for the sense of hearing.- Outer ear :The folds of cartilage surrounding the ear canal are called the pinna...

and somatosensory system

Somatosensory system

The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...

, so far.

Of sound

Hearing (or audition) is the ability to perceive sound

Sound

Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...

by detecting vibration

Vibration

Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...

s. Frequencies capable of being heard by humans are called audio

Audio frequency

An audio frequency or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human...

or sonic. The range is typically considered to be between 20 Hz

Hertz

The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

and 20,000 Hz. Frequencies higher than audio are referred to as ultrasonic

Ultrasound

Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

, while frequencies below audio are referred to as infrasonic

Infrasound

Infrasound is sound that is lower in frequency than 20 Hz or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high...

. The auditory system

Auditory system

The auditory system is the sensory system for the sense of hearing.- Outer ear :The folds of cartilage surrounding the ear canal are called the pinna...

includes the ear

Ear

The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....

s and inner structures which produce neural signals in response to the sound. The primary auditory cortex

Primary auditory cortex

The primary auditory cortex is the region of the brain that is responsible for the processing of auditory information. Corresponding roughly with Brodmann areas 41 and 42, it is located on the temporal lobe, and performs the basics of hearing—pitch and volume...

, within the temporal lobe

Temporal lobe

The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....

of the human brain, is where auditory information arrives in the cerebral cortex

Cerebral cortex

The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

.

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.

Of speech

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

Accent (linguistics)

In linguistics, an accent is a manner of pronunciation peculiar to a particular individual, location, or nation.An accent may identify the locality in which its speakers reside , the socio-economic status of its speakers, their ethnicity, their caste or social class, their first language In...

and mood of the speaker. Listeners manage to perceive words across this wide range of different conditions. Another variation is that reverberation

Reverberation

Reverberation is the persistence of sound in a particular space after the original sound is removed. A reverberation, or reverb, is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air...

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.

The process of perceiving speech begins at the level of the sound signal and the process of audition

Hearing

Hearing may refer to:* Hearing , the sense by which sound is perceived* Hearing , a person who has hearing within normal parameters* Hearing , a legal proceeding before a court or other decision making body or officer...

. 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

Morphology (linguistics)

In linguistics, morphology is the identification, analysis and description, in a language, of the structure of morphemes and other linguistic units, such as words, affixes, parts of speech, intonation/stress, or implied context...

, syntax

Syntax

In linguistics, syntax is the study of the principles and rules for constructing phrases and sentences in natural languages....

, or semantics

Semantics

Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....

may interact with basic speech perception processes to aid in recognition of speech sounds. 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.

Touch

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

Proprioception

Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement...

of hand position and conformation. People can rapidly and accurately identify three-dimensional objects by touch. This involves exploratory procedures, such as moving the fingers over the outer surface of the object or holding the entire object in the hand. Haptic perception relies on the forces experienced during touch.

Gibson defined the haptic system as "The sensibility of the individual to the world adjacent to his body by use of his body". 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

Extended physiological proprioception

Extended physiological proprioception is a concept pioneered by D.C. Simpson to describe the ability to perceive at the tip of the tool, in this case a prosthetic limb. The work was based on pneumatic prosthesis developed in response to disabilities incurred by infants as the result of use of...

according to which, when using a tool such as a stick, perceptual experience is transparently transferred to the end of the tool.

Taste

Taste (or, the more formal term, gustation) is the ability to perceive the flavor

Flavor

Flavor or flavour is the sensory impression of a food or other substance, and is determined mainly by the chemical senses of taste and smell. The "trigeminal senses", which detect chemical irritants in the mouth and throat as well as temperature and texture, are also very important to the overall...

of substances including, but not limited to, food

Food

Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

. Humans receive tastes through sensory organs called taste bud
Taste bud
Taste buds contain the receptors for taste. They are located around the small structures on the upper surface of the tongue, soft palate, upper esophagus and epiglottis, which are called papillae. These structures are involved in detecting the five elements of taste perception: salty, sour,...

s, or gustatory calyculi, concentrated on the upper surface of the tongue

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

. The human tongue has 100 to 150 taste receptor cells on each of its roughly ten thousand taste buds. There are five primary tastes: sweetness

Sweetness

Sweetness is one of the five basic tastes and is almost universally regarded as a pleasurable experience. Foods rich in simple carbohydrates such as sugar are those most commonly associated with sweetness, although there are other natural and artificial compounds that are sweet at much lower...

, bitterness, sourness, saltiness, and umami

Umami

Umami , popularly referred to as savoriness, is one of the five basic tastes together with sweet, sour, bitter, and salty.-Etymology:Umami is a loanword from the Japanese meaning "pleasant savory taste". This particular writing was chosen by Professor Kikunae Ikeda from umai "delicious" and mi ...

. Other tastes can be mimicked by combining these basic tastes. The recognition and awareness of umami is a relatively recent development in Western cuisine. The basic tastes contribute only partially to the sensation and flavor

Flavor

of food in the mouth — other factors include smell

Odor

An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also commonly called scents, which can refer to both pleasant and unpleasant odors...

, detected by the olfactory epithelium

Olfactory epithelium

The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. In humans, it measures about 1 square centimetre and lies on the roof of the nasal cavity about 7 cm above and behind the nostrils...

of the nose; texture, detected through a variety of mechanoreceptor

Mechanoreceptor

A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. There are four main types in the glabrous skin of humans: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles...

s, muscle nerves, etc.; and temperature, detected by thermoreceptor

Thermoreceptor

A thermoreceptor is a sensory receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range...

s. All basic tastes are classified as either appetitive or aversive, depending upon whether the things they sense are harmful or beneficial.

Of the social world

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

Social cognition

Social cognition is the encoding, storage, retrieval, and processing, in the brain, of information relating to conspecifics, or members of the same species. At one time social cognition referred specifically to an approach to social psychology in which these processes were studied according to the...

External links

Theories of Perception Several different aspects on perception
Richard L Gregory Theories of Richard. L. Gregory.
Optical Illusions Examples of well-known optical illusions.

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Process and terminology

Perception and reality

Constancy

Grouping

Contrast effects

Effect of experience

Effect of motivation and expectation

Perception as hypothesis-testing

Perception-in-action

Evolutionary psychology and perception

Theories of visual perception

Physiology

Of sound

Of speech

Touch

Taste

Of the social world

See also

Further reading

External links