Perception
Perception (from Latin perceptio 'gathering, receiving') is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment.[2] All perception involves signals that go through the nervous system, which in turn result from physical or chemical stimulation of the sensory system.[3] Vision involves light striking the retina of the eye; smell is mediated by odor molecules; and hearing involves pressure waves.
For other uses, see Perception (disambiguation).
Perception is not only the passive receipt for of these signals, but it is also shaped by the recipient's learning, memory, expectation, and attention.[4][5] Sensory input is a process that transforms this low-level information to higher-level information (e.g., extracts shapes for object recognition).[5] 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.[3] Since the rise of experimental psychology in the 19th century, psychology's understanding of perception has progressed by combining a variety of techniques.[4] Psychophysics quantitatively describes the relationships between the physical qualities of the sensory input and perception.[6] 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, smell or color exist in objective reality rather than in the mind of the perceiver.[4]
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.[4] 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.[4]
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.[7]
Reality[edit]
In the case of visual perception, some people can see the percept shift in their mind's eye.[54] 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 and biological mimicry. 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.[55]
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 a holistic approach.
Theories[edit]
Perception as direct perception (Gibson)[edit]
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.[75] Sensations require 'enriching', which is the role of the mental model.
The perceptual ecology approach was introduced by professor James J. Gibson, who rejected the assumption of a poverty of stimulus 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."[76] He and the psychologists who work within this paradigm detailed how the world could be specified to a mobile, exploring organism via the lawful projection of information about the world into energy arrays.[77] "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.[78]
Perception-in-action[edit]
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, 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.[79] 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.[80]
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[edit]
Many philosophers, such as Jerry Fodor, write that the purpose of perception is knowledge. However, evolutionary psychologists hold that the primary purpose of perception is to guide action.[81] They give the example of depth perception, which seems to have evolved not to aid in knowing the distances to other objects but rather to aid movement.[81] 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.[81] 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 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.[81]
Scientists who study perception and sensation have long understood the human senses as adaptations.[81] Depth perception consists of processing over half a dozen visual cues, each of which is based on a regularity of the physical world.[81] Vision evolved to respond to the narrow range of electromagnetic energy that is plentiful and that does not pass through objects.[81] 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.[81] Taste and smell respond to chemicals in the environment that were significant for fitness in the environment of evolutionary adaptedness.[81] The sense of touch is actually many senses, including pressure, heat, cold, tickle, and pain.[81] Pain, while unpleasant, is adaptive.[81] An important adaptation for senses is range shifting, by which the organism becomes temporarily more or less sensitive to sensation.[81] For example, one's eyes automatically adjust to dim or bright ambient light.[81] 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.[81]
Evolutionary psychologists claim that perception demonstrates the principle of modularity, with specialized mechanisms handling particular perception tasks.[81] For example, people with damage to a particular part of the brain are not able to recognize faces (prosopagnosia).[81] Evolutionary psychology suggests that this indicates a so-called face-reading module.[81]
Closed-loop perception[edit]
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.[82][83][84][85] Closed-loop perception appears consistent with anatomy and with the fact that perception is typically an incremental process. Repeated encounters with an object, whether conscious or not, enable an animal to refine its impressions of that object. This can be achieved more easily with a circular closed-loop system than with a linear open-loop one. Closed-loop perception can explain many of the phenomena that open-loop perception struggles to account for. This is largely because closed-loop perception considers motion to be an integral part of perception, and not an interfering component that must be corrected for. Furthermore, an environment perceived via sensor motion, and not despite sensor motion, need not be further stabilized by internal processes.[85]