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Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system, which in turn result from physical or chemical stimulation of the sensory system.Goldstein (2009) pp. 5–7 Vision involves light striking the retina of the eye; smell is mediated by odor molecules; and hearing involves pressure waves. Perception is not only the passive receipt of these signals, but it is also shaped by the recipient's learning, memory, expectation, and attention. Gregory, Richard. "Perception" in Gregory, Zangwill (1987) pp. 598–601. Sensory input is a process that transforms this low-level information to higher-level information (e.g., extracts shapes for object recognition). The process that follows connects a person's concepts and expectations (or knowledge), restorative and selective mechanisms (such as attention) that influence perception. 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 in the 19th century, psychology's understanding of perception has progressed by combining a variety of techniques. Psychophysics quantitatively describes the relationships between the physical qualities of the sensory input and perception. Sensory neuroscience studies the neural 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
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
, smell or color exist in objective reality rather than in the mind of the perceiver. Although people traditionally viewed the senses 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. 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. The perceptual systems of the brain enable individuals to see the world around them as stable, even though the sensory information is typically incomplete and rapidly varying. Human and other 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, taste is strongly influenced by smell.


Process and terminology

The process of perception begins with an object in the real world, known as the '' distal stimulus'' or ''distal object''.Goldstein (2009) pp. 5–7 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''.Pomerantz, James R. (2003): "Perception: Overview". In: Lynn Nadel (Ed.), ''Encyclopedia of Cognitive Science'', Vol. 3, London: Nature Publishing Group, pp. 527–537. This raw pattern of neural activity is called the ''proximal stimulus''. These neural signals are then transmitted to the brain and processed. The resulting mental re-creation of the distal stimulus is the ''percept''. To explain the process of perception, an example could be an ordinary shoe. The shoe itself is the distal stimulus. When light from the shoe enters a person's eye and stimulates the retina, that stimulation is the proximal stimulus. The image of the shoe reconstructed by the brain of the person is the percept. Another example could be a ringing telephone. The ringing of the phone is the distal stimulus. The sound stimulating a person's auditory receptors is the proximal stimulus. 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'' or ''stimulus modalities''.


Bruner's model of the perceptual process

Psychologist Jerome Bruner developed a model of perception, in which people put "together the information contained in" a target and a situation to form "perceptions of ourselves and others based on social categories."Alan S. & Gary J. (2011). Perception, Attribution, and Judgment of Others. Organizational Behaviour: Understanding and Managing Life at Work, Vol. 7. This model is composed of three states: # When people encounter an unfamiliar target, they are very open to the informational cues contained in the target and the situation surrounding it. # The first stage does not give people enough information on which to base perceptions of the target, so they will actively seek out cues to resolve this ambiguity. Gradually, people collect some familiar cues that enable them to make a rough categorization of the target. # The cues become less open and selective. People try to search for more cues that confirm the categorization of the target. They actively ignore and distort cues that violate their initial perceptions. Their perception becomes more selective and they finally paint a consistent picture of the target.


Saks and John's three components to perception

According to Alan Saks and Gary Johns, there are three components to perception: #The Perceiver: a person whose awareness is focused on the stimulus, and thus begins to perceive it. There are many factors that may influence the perceptions of the perceiver, while the three major ones include (1) motivational state, (2) emotional state, and (3) experience. All of these factors, especially the first two, greatly contribute to how the person perceives a situation. Oftentimes, the perceiver may employ what is called a "perceptual defense," where the person will only see what they want to see. #The Target: the ''object'' of perception; something or someone who is being perceived. The amount of information gathered by the sensory organs of the perceiver affects the interpretation and understanding about the target. #The Situation: the ''environmental'' factors, timing, and degree of stimulation that affect the process of perception. These factors may render a single stimulus to be left as merely a stimulus, not a percept that is subject for brain interpretation.


Multistable perception

Stimuli are not necessarily translated into a percept and rarely does a single stimulus translate into a percept. An ambiguous stimulus may sometimes be transduced into one or more percepts, experienced randomly, one at a time, in a process termed '' multistable perception''. 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 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.


Types of perception


Vision

In many ways, vision is the primary human sense. Light is taken in through each eye and focused in a way which sorts it on the retina according to direction of origin. A dense surface of photosensitive cells, including rods, cones, and intrinsically photosensitive retinal ganglion cells captures information about the intensity, color, and position of incoming light. Some processing of texture and movement occurs within the neurons on the retina before the information is sent to the brain. In total, about 15 differing types of information are then forwarded to the brain proper via the optic nerve. The timing of perception of a visual event, at points along the visual circuit, have been measured. A sudden alteration of light at a spot in the environment first alters photoreceptor cells in the retina, which send a signal to the retina bipolar cell layer which, in turn, can activate a retinal ganglion neuron cell. A retinal ganglion cell is a bridging neuron that connects visual retinal input to the visual processing centers within the central nervous system. Light-altered neuron activation occurs within about 5–20 milliseconds in a rabbit retinal ganglion, although in a mouse retinal ganglion cell the initial spike takes between 40 and 240 milliseconds before the initial activation. The initial activation can be detected by an action potential spike, a sudden spike in neuron membrane electric voltage. A perceptual visual event measured in humans was the presentation to individuals of an anomalous word. If these individuals are shown a sentence, presented as a sequence of single words on a computer screen, with a puzzling word out of place in the sequence, the perception of the puzzling word can register on an electroencephalogram (EEG). In an experiment, human readers wore an elastic cap with 64 embedded electrodes distributed over their scalp surface. Within 230 milliseconds of encountering the anomalous word, the human readers generated an event-related electrical potential alteration of their EEG at the left occipital-temporal channel, over the left occipital lobe and temporal lobe.


Sound

Hearing (or ''audition'') is the ability to perceive
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
by detecting
vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic function, periodic, such as the motion of a pendulum ...
s (i.e., ''sonic'' detection). Frequencies capable of being heard by humans are called ''audio'' or ''audible'' ''frequencies'', the range of which is typically considered to be between 20  Hz and 20,000 Hz. Frequencies higher than audio are referred to as ''ultrasonic'', while frequencies below audio are referred to as ''infrasonic''. The auditory system includes the outer ears, which collect and filter sound waves; the middle ear, which transforms the sound pressure ( impedance matching); and the inner ear, which produces neural signals in response to the sound. By the ascending auditory pathway these are led to the primary auditory cortex within the
temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...
of the human brain, from where the auditory information then goes to the cerebral cortex for further processing. 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 sources of interest, identifying them and often estimating their distance and direction.


Touch

The process of recognizing objects through touch is known as ''haptic perception''. 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. 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 body movement and haptic perception, where the latter 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

Taste (formally known as ''gustation'') is the ability to perceive the flavor of substances, including, but not limited to, food. Humans receive tastes through sensory organs concentrated on the upper surface of the tongue, called '' taste buds'' or ''gustatory calyculi''. The human tongue has 100 to 150 taste receptor cells on each of its roughly-ten thousand taste buds. Traditionally, there have been four primary tastes: sweetness, bitterness, sourness, and saltiness. The recognition and awareness of umami, which is considered the fifth primary taste, is a relatively recent development in Western cuisine. Other tastes can be mimicked by combining these basic tastes, all of which contribute only partially to the sensation and flavor of food in the mouth. Other factors include smell, which is detected by the olfactory epithelium of the nose; texture, which is detected through a variety of
mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force i ...
s, muscle nerves, etc.; and temperature, which is detected by
thermoreceptor A thermoreceptor is a non-specialised sense receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range. In the mammalian peripheral nervous s ...
s. All basic tastes are classified as either '' appetitive'' or '' aversive'', depending upon whether the things they sense are harmful or beneficial.Why do two great tastes sometimes not taste great together?
scientificamerican.com. Dr. Tim Jacob, Cardiff University. 22 May 2009.


Smell

Smell is the process of absorbing molecules through olfactory organs, which are absorbed by humans through the
nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for Respiration (physiology), respiration alongside the mouth. Behind the nose are the olfactory mucosa and the Paranasal sinus, sinuses. B ...
. These molecules diffuse through a thick layer of
mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
; come into contact with one of thousands of
cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryote, eukaryotic Cell (biology), cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a ...
that are projected from sensory neurons; and are then absorbed into a receptor (one of 347 or so). It is this process that causes humans to understand the concept of smell from a physical standpoint. Smell is also a very interactive sense as scientists have begun to observe that olfaction comes into contact with the other sense in unexpected ways. It is also the most primal of the senses, as it is known to be the first indicator of safety or danger, therefore being the sense that drives the most basic of human survival skills. As such, it can be a catalyst for human behavior on a
subconscious In psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, including feelings and thoughts. It is an academic dis ...
and
instinct Instinct is the inherent inclination of a life, living organism towards a particular complex behavior, behaviour, containing both innate (inborn) and learned elements. The simplest example of an instinctive behaviour is a fixed action pattern (FAP ...
ive level.


Social

Social perception Social perception (or interpersonal perception) is the study of how people form impressions of and make inferences about other people as sovereign personalities. Social perception refers to identifying and utilizing social cues to make judgments ab ...
is the part of perception that allows people to understand the individuals and groups of their social world. Thus, it is an element of
social cognition Social cognition is a sub-topic of various branches of psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, in ...
.


Speech

''Speech perception'' is the process by which
spoken language A spoken language is a language produced by articulate sounds or (depending on one's definition) manual gestures, as opposed to a written language. An oral language or vocal language is a language produced with the vocal tract in contrast with a si ...
is heard, interpreted and understood. Research in this field seeks to understand how human listeners recognize the sound of speech (or ''
phonetics Phonetics is a branch of linguistics Linguistics is the scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, parti ...
'') and use such information to understand spoken language. Listeners manage to perceive words across a wide range of conditions, as the sound of a word can vary widely according to words that surround it and the
tempo In musical terminology, tempo (Italian language, Italian, 'time'; plural ''tempos'', or ''tempi'' from the Italian plural) is the speed or pace of a given musical composition, piece. In classical music, tempo is typically indicated with an inst ...
of the speech, as well as the physical characteristics, accent, tone, and mood of the speaker.
Reverberation Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abso ...
, signifying the persistence of sound after the sound is produced, can also have a considerable impact on perception. 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 within the auditory signal and the process of
audition An audition is a sample performance by an actor, singer, musician, dancer or other performer. It typically involves the performer displaying their talent through a previously memorized and rehearsed solo piece or by performing a work or piece giv ...
. The initial auditory signal is compared with visual information—primarily lip movement—to extract acoustic cues and phonetic information. It is possible other sensory modalities are integrated at this stage as well. This speech information can then be used for higher-level language processes, such as word recognition. Speech perception is not necessarily uni-directional. Higher-level language processes connected with
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy) Galaxy morphological classification is a system used by astronomers ...
,
syntax In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentence (linguistics), sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence st ...
, and/or
semantics Semantics (from grc, wikt:σημαντικός, σημαντικός ''sēmantikós'', "significant") is the study of reference, Meaning (philosophy), meaning, or truth. The term can be used to refer to subfields of several distinct discipline ...
may also interact with basic speech perception processes to aid in recognition of speech sounds. It may be the case that it is not necessary (maybe not even possible) for a listener to recognize
phoneme In phonology and linguistics, a phoneme () is a unit of sound that can distinguish one word from another in a particular language. For example, in most List of dialects of English, dialects of English, with the notable exception of the West M ...
s before recognizing higher units, such as words. In an 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. Moreover, they were not able to accurately identify which phoneme had even been disturbed.


Faces

''Facial perception'' refers to cognitive processes specialized in handling human faces (including perceiving the identity of an individual) and facial expressions (such as emotional cues.)


Social touch

The ''somatosensory cortex'' is a part of the brain that receives and encodes sensory information from receptors of the entire body. Affective touch is a type of sensory information that elicits an emotional reaction and is usually social in nature. Such information is actually coded differently than other sensory information. Though the intensity of affective touch is still encoded in the primary somatosensory cortex, the feeling of pleasantness associated with affective touch is activated more in the
anterior cingulate cortex In the human brain, the anterior cingulate cortex (ACC) is the frontal part of the cingulate cortex that resembles a "collar" surrounding the frontal part of the corpus callosum. It consists of Brodmann areas Brodmann area 24, 24, Brodmann area ...
. Increased blood oxygen level-dependent (BOLD) contrast imaging, identified during
functional magnetic resonance imaging Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...
(fMRI), shows that signals in the anterior cingulate cortex, as well as the
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas Brodmann area 8, BA8, Brodmann area 9, BA9, Brodmann area 10, BA10, Brodmann area 11, BA ...
, are highly correlated with pleasantness scores of affective touch. Inhibitory
transcranial magnetic stimulation Transcranial magnetic stimulation (TMS) is a noninvasive form of neurostimulation, brain stimulation in which a changing magnetic field is used to induce an electric current at a specific area of the brain through electromagnetic induction. An ele ...
(TMS) of the primary somatosensory cortex inhibits the perception of affective touch intensity, but not affective touch pleasantness. Therefore, the S1 is not directly involved in processing socially affective touch pleasantness, but still plays a role in discriminating touch location and intensity.


Multi-modal perception

Multi-modal perception refers to concurrent stimulation in more than one sensory modality and the effect such has on the perception of events and objects in the world.


Time (chronoception)

Chronoception refers to how the passage of
time Time is the continued sequence of existence and event (philosophy), events that occurs in an apparently irreversible process, irreversible succession from the past, through the present, into the future. It is a component quantity of various me ...
is perceived and experienced. Although the sense of time is not associated with a specific
sensory system The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neural pathways, and parts of the brain invo ...
, the work of
psychologist A psychologist is a professional who practices psychology and studies mental states, perceptual, cognitive, emotional, and social processes and behavior. Their work often involves the experimentation, observation, and interpretation of how indi ...
s and
neuroscientist A neuroscientist (or neurobiologist) is a scientist who has specialised knowledge in neuroscience, a branch of biology that deals with the physiology, biochemistry, psychology, anatomy and molecular biology of neurons, Biological neural network, n ...
s indicates that human brains do have a system governing the perception of time, composed of a highly distributed system involving the cerebral cortex,
cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...
, and
basal ganglia The basal ganglia (BG), or basal nuclei, are a group of subcortical Nucleus (neuroanatomy), nuclei, of varied origin, in the brains of vertebrates. In humans, and some primates, there are some differences, mainly in the division of the globus p ...
. One particular component of the brain, the
suprachiasmatic nucleus The suprachiasmatic nucleus or nuclei (SCN) is a tiny region of the brain in the hypothalamus, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms. The neuronal and hormonal activities it generates regula ...
, is responsible for the
circadian rhythm A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
(commonly known as one's "internal clock"), while other cell clusters appear to be capable of shorter-range timekeeping, known as an '' ultradian rhythm''. One or more
dopaminergic pathways Dopaminergic pathways (dopamine pathways, dopaminergic projections) in the human brain The human brain is the central organ (anatomy), organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brai ...
in the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
appear to have a strong modulatory influence on
mental chronometry Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; sometimes referred to as "response time") is meas ...
, particularly interval timing.


Agency

''Sense of agency'' refers to the subjective feeling of having chosen a particular action. Some conditions, such as
schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social w ...
, can cause a loss of this sense, which may lead a person into delusions, such as feeling like a machine or like an outside source is controlling them. An opposite extreme can also occur, where people experience everything in their environment as though they had decided that it would happen. Even in non-
pathological Pathology is the study of the causal, causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when us ...
cases, there is a measurable difference between the making of a decision and the feeling of agency. Through methods such as the Libet experiment, a gap of half a second or more can be detected from the time when there are detectable neurological signs of a decision having been made to the time when the subject actually becomes conscious of the decision. There are also experiments in which an illusion of agency is induced in psychologically normal subjects. In 1999, psychologists Wegner and Wheatley gave subjects instructions to move a mouse around a scene and point to an image about once every thirty seconds. However, a second person—acting as a test subject but actually a confederate—had their hand on the mouse at the same time, and controlled some of the movement. Experimenters were able to arrange for subjects to perceive certain "forced stops" as if they were their own choice.


Familiarity

Recognition memory Recognition memory, a subcategory of declarative memory, is the ability to recognize previously encountered events, objects, or people.Medina, J. J. (2008)The biology of recognition memory. ''Psychiatric Times''. When the previously experienced eve ...
is sometimes divided into two functions by neuroscientists: ''familiarity'' and ''recollection''. A strong sense of familiarity can occur without any recollection, for example in cases of deja vu. The
temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...
(specifically the
perirhinal cortex The perirhinal cortex is a brain cortex, cortical region in the medial temporal lobe that is made up of Brodmann areas Brodmann area 35, 35 and Brodmann area 36, 36. It receives highly processed sensory information from all sensory regions, and is ...
) responds differently to stimuli that feel novel compared to stimuli that feel familiar. Firing rates in the perirhinal cortex are connected with the sense of familiarity in humans and other mammals. In tests, stimulating this area at 10–15 Hz caused animals to treat even novel images as familiar, and stimulation at 30–40 Hz caused novel images to be partially treated as familiar. In particular, stimulation at 30–40 Hz led to animals looking at a familiar image for longer periods, as they would for an unfamiliar one, though it did not lead to the same exploration behavior normally associated with novelty. Recent studies on
lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or Trauma (medicine), trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no ...
s in the area concluded that rats with a damaged perirhinal cortex were still more interested in exploring when novel objects were present, but seemed unable to tell novel objects from familiar ones—they examined both equally. Thus, other brain regions are involved with noticing unfamiliarity, while the perirhinal cortex is needed to associate the feeling with a specific source.


Sexual stimulation

Sexual stimulation Sexual stimulation is any stimulation, stimulus (including bodily contact) that leads to, enhances and maintains sexual arousal, and may lead to orgasm. Although sexual arousal may arise without physical stimulation, achieving orgasm usually requ ...
is any stimulus (including bodily contact) that leads to, enhances, and maintains
sexual arousal Sexual arousal (also known as sexual excitement) describes the Physiology, physiological and psychological responses in preparation for sexual intercourse or when exposed to Sexual stimulation, sexual stimuli. A number of physiological respons ...
, possibly even leading to
orgasm Orgasm (from Greek language, Greek , ; "excitement, swelling") or sexual climax is the sudden discharge of accumulated sexual excitement during the Human sexual response cycle, sexual response cycle, resulting in rhythmic, involuntary Muscle ...
. Distinct from the general sense of
touch In physiology, the somatosensory system is the network of Nervous system, neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), ...
, sexual stimulation is strongly tied to hormonal activity and chemical triggers in the body. Although sexual arousal may arise without physical stimulation, achieving orgasm usually requires physical sexual stimulation (stimulation of the Krause-Finger corpuscles found in erogenous zones of the body.)


Other senses

Other senses enable perception of body balance,
acceleration In mechanics, acceleration is the Rate (mathematics), rate of change of the velocity of an object with respect to time. Accelerations are Euclidean vector, vector quantities (in that they have Magnitude (mathematics), magnitude and Direction ...
,
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong ...
, position of body parts, temperature, and pain. They can also enable perception of internal senses, such as
suffocation Asphyxia or asphyxiation is a condition of deficient supply of oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the period ...
,
gag reflex The pharyngeal reflex or gag reflex is a reflex muscular contraction of the back of the throat, evoked by touching the roof of the mouth, the back of the tongue, the area around the tonsils, the palatine uvula, uvula, and the back of the throat. It, ...
,
abdominal distension Abdominal distension occurs when substances, such as air (gas) or fluid, accumulate in the abdomen causing its expansion. It is typically a symptom of an underlying disease or dysfunction in the body, rather than an illness in its own right. Pe ...
, fullness of
rectum The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the s ...
and
urinary bladder The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...
, and sensations felt in the
throat In vertebrate anatomy, the throat is the front part of the neck, internally positioned in front of the vertebra, vertebrae. It contains the Human pharynx, pharynx and larynx. An important section of it is the epiglottis, separating the esophagus f ...
and
lung The lungs are the primary Organ (anatomy), organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the vertebral co ...
s.


Reality

In the case of visual perception, some people can see the percept shift in their
mind's eye A mental image is an experience that, on most occasions, significantly resembles the experience of 'perceiving' some object, event, or scene, but occurs when the relevant object, event, or scene is not actually present to the senses. There are ...
. Others, who are not picture thinkers, may not necessarily perceive the 'shape-shifting' as their world changes. This esemplastic nature has been demonstrated by an experiment that showed that ambiguous images have multiple interpretations on the perceptual level. The confusing ambiguity of perception is exploited in human technologies such as
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
and biological
mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry f ...
. For example, the wings of European peacock butterflies bear eyespots 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" in order 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 laws in psychology are Weber's law, which states that the smallest noticeable difference in stimulus intensity is proportional to the intensity of the reference; and Fechner's law, which quantifies the relationship between the intensity of the physical stimulus and its perceptual counterpart (e.g., 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 an emphasis on
holistic Holism () is the idea that various systems (e.g. physical, biological, social) should be viewed as wholes, not merely as a collection of parts. The term "holism" was coined by Jan Smuts in his 1926 book ''Holism and Evolution''."holism, n." OED Onl ...
approach.


Physiology

A ''sensory system'' is a part of the nervous system responsible for processing sensory information. A sensory system consists of
sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of Stimulus (physiology), stimulus, via their Receptor (biochemistry), receptors, into action potentials or graded potentials. This ...
s,
neural pathway In neuroanatomy Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry ...
s, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for
vision Vision, Visions, or The Vision may refer to: Perception Optical perception * Visual perception, the sense of sight * Visual system, the physical mechanism of eyesight * Computer vision, a field dealing with how computers can be made to gain und ...
,
hearing Hearing, or auditory perception, is the ability to perceive Sound, sounds through an organ, such as an ear, by detecting Vibration, vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with he ...
,
somatic sensation In physiology, the somatosensory system is the network of Nervous system, neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), ...
(touch), taste and
olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it ...
(smell), as listed above. It has been suggested that the immune system is an overlooked sensory modality. In short, senses are
transducers A transducer is a device that Energy transformation, converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, M ...
from the physical world to the realm of the mind. The
receptive field The receptive field, or sensory space, is a delimited medium where some Stimulus (physiology), physiological stimuli can evoke a Sensory neuron, sensory neuronal response in specific organisms. Complexity of the receptive field ranges from the un ...
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 A cone is a three-dimensional Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position (geometry), ...
can see, is its receptive field. Receptive fields have been identified for the
visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the a ...
, auditory system and
somatosensory system In physiology, the somatosensory system is the network of Nervous system, neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), ...
, so far. Research attention is currently focused not only on external perception processes, but also to "
interoception Interoception is contemporarily defined as the collection of Sense#Other internal sensations and perceptions, senses perceiving the internal state of the body. This can be both conscious and unconscious. It encompasses the brain's process of inte ...
", considered as the process of receiving, accessing and appraising internal bodily signals. Maintaining desired physiological states is critical for an organism's well-being and survival. Interoception is an iterative process, requiring the interplay between perception of body states and awareness of these states to generate proper self-regulation. Afferent sensory signals continuously interact with higher order cognitive representations of goals, history, and environment, shaping emotional experience and motivating regulatory behavior.


Features


Constancy

''Perceptual constancy'' is the ability of perceptual systems to recognize the same object from widely varying sensory inputs. For example, individual people can be recognized 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 recognized 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 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 f ...
'': for example, a white piece of paper can be recognized 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, with phonemic restoration as a notable example from hearing.


Grouping (Gestalt)

The ''principles of grouping'' (or ''Gestalt laws of grouping'') are a set of principles in
psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, including feelings and thoughts. It is an academic discipline of immens ...
, 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: # Proximity: 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. # Similarity: 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 that are different as part of a separate object. This allows for people to distinguish between adjacent and overlapping objects based on their visual texture and resemblance. # Closure: 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. # Good Continuation: 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. # Common Fate: 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 (; 29 August 1632 – 28 October 1704) was an English philosopher and physician, widely regarded as one of the most influential of Age of Enlightenment, Enlightenment thinkers and commonly known as the "father of liberalism ...
, 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 Maximilian Wundt (; ; 16 August 1832 – 31 August 1920) was a German physiologist, philosopher, and professor, known today as one of the fathers of modern psychology. Wundt, who distinguished psychology as a science from philosophy and ...
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 pleasant or unpleasant. 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. In the brain, brightness contrast exerts effects on both neuronal firing rates and neuronal synchrony.


Theories


Perception as direct perception (Gibson)

Cognitive theories of perception assume there is a poverty of stimulus. This is the claim that sensations, by themselves, are unable to provide a unique description of the world. Sensations require 'enriching', which is the role of the
mental model A mental model is an explanation of someone's thought process about how something works in the real world. It is a representation of the surrounding world, the relationships between its various parts and a person's intuitive perception about thei ...
. The perceptual ecology approach was introduced by James J. Gibson, who rejected the assumption of a
poverty of stimulus Poverty of the stimulus (POS) is the controversial argument from linguistics Linguistics is the scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise anal ...
and the idea that perception is based upon sensations. Instead, Gibson 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 In science and philosophy, a paradigm () is a distinct set of concepts or thought patterns, including theories, research methods, postulates, and standards for what constitute legitimate contributions to a field. Etymology ''Paradigm'' comes f ...
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" would be 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 Direct may refer to: Mathematics * Directed set In mathematics, a directed set (or a directed preorder or a filtered set) is a nonempty Set (mathematics), set A together with a Reflexive relation, reflexive and Transitive relation, transitive ...
.


Perception-in-action

From Gibson's early work derived an ecological understanding of perception known as ''perception-in-action,'' which argues that perception is a requisite property of animate action. It posits that, without perception, action would be unguided, and without action, perception would serve no purpose. Animate actions require both perception and motion, which 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 home in upon them. The constructivist view, held by such philosophers as
Ernst von Glasersfeld Ernst von Glasersfeld (March 8, 1917, Munich Munich ( ; german: München ; bar, Minga ) is the capital and most populous city of the States of Germany, German state of Bavaria. With a population of 1,558,395 inhabitants as of 31 July 2 ...
, 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. 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. According to this theory, "tau information", or time-to-goal information is the fundamental ''percept'' in perception.


Evolutionary psychology

Many philosophers, such as
Jerry Fodor Jerry Alan Fodor (; April 22, 1935 – November 29, 2017) was an American philosopher and the author of many crucial works in the fields of philosophy of mind and cognitive science. His writings in these fields laid the groundwork for the modula ...
, write that the purpose of perception is knowledge. However, evolutionary psychologists hold that the primary purpose of perception is to guide action.Gaulin, Steven J. C. and Donald H. McBurney. Evolutionary Psychology.
Prentice Hall Prentice Hall was an American major educational publisher owned by Savvas Learning Company. Prentice Hall publishes print and digital content for the 6–12 and higher-education market, and distributes its technical titles through the Safari B ...
. 2003. , Chapter 4, pp. 81–101.
They give the example of
depth perception Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three-dimensional, three dimensions. Depth perception happens primarily d ...
, which seems to have evolved not to aid in knowing the distances to other objects but rather to aid movement. Evolutionary psychologists argue that animals ranging from fiddler crabs to humans use eyesight for collision avoidance, suggesting that vision is basically for directing action, not providing knowledge. Neuropsychologists showed that perception systems evolved along the specifics of animals' activities. This explains why bats and worms can perceive different frequency of auditory and visual systems than, for example, humans. Building and maintaining sense organs is
metabolically Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a quality that distinguishes matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes, from t ...
expensive. More than half the brain is devoted to processing sensory information, and the brain itself consumes roughly one-fourth of one's metabolic resources. Thus, such organs evolve only when they provide exceptional benefits to an organism's fitness. 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 environment of evolutionary adaptedness. 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 co-evolve, 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 are not able to recognize faces (''
prosopagnosia Prosopagnosia (from Greek ''prósōpon'', meaning "face", and ''agnōsía'', meaning "non-knowledge"), also called face blindness, (" illChoisser had even begun tpopularizea name for the condition: face blindness.") is a cognitive disorder of ...
''). Evolutionary psychology suggests that this indicates a so-called face-reading module.


Closed-loop perception

The theory of closed-loop perception proposes dynamic motor-sensory closed-loop process in which information flows through the environment and the brain in continuous loops.Friston, K. (2010
The free-energy principle: a unified brain theory?
nature reviews neuroscience 11:127-38
Tishby, N. and D. Polani
Information theory of decisions and actions
in Perception-Action Cycle. 2011, Springer. p. 601-636.


Feature integration theory

Anne Treisman's feature integration theory (FIT) attempts to explain how characteristics of a stimulus such as physical location in space, motion, color, and shape are merged to form one percept despite each of these characteristics activating separate areas of the cortex. FIT explains this through a two part system of perception involving the preattentive and focused attention stages. The preattentive stage of perception is largely unconscious, and analyzes an object by breaking it down into its basic features, such as the specific color, geometric shape, motion, depth, individual lines, and many others. Studies have shown that, when small groups of objects with different features (e.g., red triangle, blue circle) are briefly flashed in front of human participants, many individuals later report seeing shapes made up of the combined features of two different stimuli, thereby referred to as
illusory conjunctions Illusory conjunctions are psychological effects in which participants combine features of two objects into one object. There are visual illusory conjunctions, auditory illusion, auditory illusory conjunctions, and illusory conjunctions produced by ...
. The unconnected features described in the preattentive stage are combined into the objects one normally sees during the focused attention stage. The focused attention stage is based heavily around the idea of attention in perception and 'binds' the features together onto specific objects at specific spatial locations (see the binding problem).


Other theories of perception

* Enactivism * The Interactive Activation and Competition Model * Recognition-By-Components Theory ( Irving Biederman)


Effects on perception


Effect of experience

With experience,
organism In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multicellular o ...
s 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 Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedality, bipedalism and exceptional cognitive skills due to a large and complex Human brain, brain. This has enabled the development of ad ...
sphere.
Research Research is "creativity, creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular att ...
has focused on the relation of this to other kinds of
learning Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machine learning, machines ...
, and whether it takes place in peripheral sensory systems or in the brain's processing of sense information.
Empirical Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences and ...
research Research is "creativity, creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular att ...
show that specific practices (such as
yoga Yoga (; sa, योग, lit=yoke' or 'union ) is a group of Asana, physical, mental, and Spirituality#Asian traditions, spiritual practices or disciplines which originated in History of India, ancient India and aim to control (yoke) and Ś ...
,
mindfulness Mindfulness is the practice of purposely bringing one's attention to the present-moment experience without evaluation, a skill one develops through meditation or other training. Mindfulness derives from ''sati'', a significant element of Hi ...
,
Tai Chi Tai chi (), short for Tai chi ch'üan ( zh, s=太极拳, t=太極拳, first=t, p=Tàijíquán, labels=no), sometimes called "shadowboxing", is an neijia, internal Chinese martial art practiced for defense training, health benefits and medita ...
,
meditation Meditation is a practice in which an individual uses a technique – such as mindfulness, or focusing the mind on a particular object, thought, or activity – to train attention and awareness, and achieve a mentally clear and emotionally calm ...
, Daoshi and other mind-body disciplines) can modify human perceptual modality. Specifically, these practices enable perception skills to switch from the external (exteroceptive field) towards a higher ability to focus on internal signals ('' proprioception''). Also, when asked to provide verticality judgments, highly self-transcendent
yoga Yoga (; sa, योग, lit=yoke' or 'union ) is a group of Asana, physical, mental, and Spirituality#Asian traditions, spiritual practices or disciplines which originated in History of India, ancient India and aim to control (yoke) and Ś ...
practitioners were significantly less influenced by a misleading visual context. Increasing self-transcendence may enable yoga practitioners to optimize verticality judgment tasks by relying more on internal (vestibular and proprioceptive) signals coming from their own body, rather than on exteroceptive, visual cues. Past actions and events that transpire right before an encounter or any form of stimulation have a strong degree of influence on how sensory stimuli are processed and perceived. On a basic level, the information our senses receive is often ambiguous and incomplete. However, they are grouped together in order for us to be able to understand the physical world around us. But it is these various forms of stimulation, combined with our previous knowledge and experience that allows us to create our overall perception. For example, when engaging in conversation, we attempt to understand their message and words by not only paying attention to what we hear through our ears but also from the previous shapes we have seen our mouths make. Another example would be if we had a similar topic come up in another conversation, we would use our previous knowledge to guess the direction the conversation is headed in.


Effect of motivation and expectation

A ''perceptual set'' (also called ''perceptual expectancy'' or simply ''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 is the reason for which humans and other animals initiate, continue, or terminate a behavior at a given time. Motivational states are commonly understood as forces acting within the agent that create a disposition to engage in goal-dire ...
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. When someone has a reputation for being funny, an audience is 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 A playing card is a piece of specially prepared card stock, heavy paper, thin cardboard, plastic-coated paper, cotton-paper blend, or thin plastic that is marked with distinguishing motifs. Often the front (face) and back of each card has a Pap ...
reversed the color of the
suit A suit, lounge suit, or business suit is a set of clothes comprising a suit jacket and trousers of identical textiles worn with a collared dress shirt, necktie, and dress shoes. A skirt suit is similar, but with a matching skirt instead of tr ...
symbol for some cards (e.g. red spades and black hearts). Philosopher
Andy Clark Andy Clark, (born 1957) is a British people, British philosopher who is Professor of Cognitive Philosophy at the University of Sussex. Prior to this, he was at professor of philosophy and Chair (official), Chair in Logic and Metaphysics at th ...
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 In neuroscience Neuroscience is the science, scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a Multidisciplinary approach, multidisciplinary science that comb ...
''. 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 is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machine learning, machines ...
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). Indeed, predictive coding provides an account where this type of feedback assists in stabilizing our inference-making process about the physical world, such as with perceptual constancy examples.
Embodied cognition Embodied cognition is the theory that many features of cognition, whether human or otherwise, are shaped by aspects of an organism's entire body. Sensory and motor systems are seen as fundamentally integrated with cognitive processing. The cognit ...
challenges the idea of perception as internal representations resulting from a passive reception of (incomplete) sensory inputs coming from the outside world. According to O'Regan (1992), the major issue with this perspective is that it leaves the subjective character of perception unexplained. Thus, perception is understood as an active process conducted by perceiving and engaged agents (perceivers). Furthermore, perception is influenced by agents' motives and expectations, their bodily states, and the interaction between the agent's body and the environment around it.


See also


References


Citations


Sources


Bibliography

* Arnheim, R. (1969). ''Visual Thinking''. Berkeley: University of California Press. . * Flanagan, J. R., & Lederman, S. J. (2001). "'Neurobiology: Feeling bumps and holes. News and Views", ''Nature'', 412(6845):389–91.
PDF
* Gibson, J. J. (1966). ''The Senses Considered as Perceptual Systems'', Houghton Mifflin. * Gibson, J. J. (1987). ''The Ecological Approach to Visual Perception''. Lawrence Erlbaum Associates. * Robles-De-La-Torre, G. (2006). "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.
PDF


External links



Several different aspects on perception
Richard L Gregory
Theories of Richard. L. Gregory.
Comprehensive set of optical illusions
presented by Michael Bach.
Optical Illusions
Examples of well-known optical illusions.
The Epistemology of Perception
Article in the ''
Internet Encyclopedia of Philosophy The ''Internet Encyclopedia of Philosophy'' (''IEP'') is a scholarly online encyclopedia, dealing with philosophy, Philosophy, philosophical topics, and philosophers. The IEP combines open access publication with peer reviewed publication of ori ...
''
Cognitive Penetrability of Perception and Epistemic Justification
Article in the ''
Internet Encyclopedia of Philosophy The ''Internet Encyclopedia of Philosophy'' (''IEP'') is a scholarly online encyclopedia, dealing with philosophy, Philosophy, philosophical topics, and philosophers. The IEP combines open access publication with peer reviewed publication of ori ...
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