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In philosophy, psychology, and the cognitive sciences, perception is the process of attaining awareness or understanding of sensory information. The word "perception" comes from the Latin words perceptio, percipio, and means "receiving, collecting, action of taking possession, apprehension with the mind or senses."

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. The study of perception gave rise to the Gestalt school of psychology, with its emphasis on holistic approach.

What one perceives is a result of interplays between past experiences, including one’s culture, and the interpretation of the perceived. If the percept does not have support in any of these perceptual bases it is unlikely to rise above perceptual threshold.

Types

Two types of consciousness are considerable regarding perception: phenomenal (any occurrence that is observable and physical) and psychological. The difference everybody can demonstrate to him- or herself is by the simple opening and closing of his or her eyes: phenomenal consciousness is thought, on average, to be predominately absent without sight. Through the full or rich sensations present in sight, nothing by comparison is present while the eyes are closed. Using this precept, it is understood that, in the vast majority of cases, logical solutions are reached through simple human sensation.

The analogy of Plato's Cave was coined to express these ideas.

Passive perception (conceived by René Descartes) can be surmised as the following sequence of events: surrounding → input (senses) → processing (brain) → output (re-action). Although still supported by mainstream philosophers, psychologists and neurologists, this theory is nowadays losing momentum. The theory of active perception has emerged from extensive research of sensory illusions, most notably the works of Richard L. Gregory. This theory, which is increasingly gaining experimental support, can be surmised as dynamic relationship between "description" (in the brain) ↔ senses ↔ surrounding, all of which holds true to the linear concept of experience.

Perception and reality

Ambiguous images


In the case of visual perception, some people can actually see the percept shift in their mind's eye. Others, who are not picture thinker, may not necessarily perceive the 'shape-shifting' as their world changes. The 'esemplastic' nature has been shown by experiment: an ambiguous image has multiple interpretations on the perceptual level. The question, "Is the glass half empty or half full?" serves to demonstrate the way an object can be perceived in different ways.

Just as one object can give rise to multiple percepts, so an object may fail to give rise to any percept at all: if the percept has no grounding in a person's experience, the person may literally not perceive it.

The processes of perception routinely alter what humans see. When people view something with a preconceived concept about it, they tend to take those concepts and see them whether or not they are there. This problem stems from the fact that humans are unable to understand new information, without the inherent bias of their previous knowledge. A person’s knowledge creates his or her reality as much as the truth, because the human mind can only contemplate that to which it has been exposed. When objects are viewed without understanding, the mind will try to reach for something that it already recognizes, in order to process what it is viewing. That which most closely relates to the unfamiliar from our past experiences, makes up what we see when we look at things that we don’t comprehend.

This confusing ambiguity of perception is exploited in human technologies such as camouflage, and also in biological mimicry, for example by Peacock butterflies, whose wings bear eye markings that birds respond to as though they were the eyes of a dangerous predator. Perceptual ambiguity is not restricted to vision. For example, recent touch perception research Robles-De-La-Torre & Hayward 2001 found that kinesthesia based haptic perception strongly relies on the forces experienced during touch.

Cognitive theories of perception assume there is a poverty of stimulus. This (with reference to perception) is the claim that sensations are, by themselves, unable to provide a unique description of the world. Sensations require 'enriching', which is the role of the mental model. A different type of theory is the perceptual ecology approach of James J. Gibson. Gibson rejected the assumption of a poverty of stimulus by rejecting the notion that perception is based in sensations. Instead, he investigated what information is actually presented to the perceptual systems. 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. 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.

Preconceptions can influence how the world is perceived. For example, one classic psychological experiment showed slower reaction times and less accurate answers when a deck of playing cards reversed the color of the suit symbol for some cards (e.g. red spades and black hearts).

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-in-action

The ecological understanding of perception derives from Gibson's early work is perception-in-action, the notion that perception is a requisite property of animate action; without perception action would not be guided and without action perception would be pointless. Animate actions require perceiving and moving together. In a sense, "perception and movement are two sides of the same coin, the coin is action." One aspect of Gibson's approach has been questioned however: it is his implicit belief that singular entities, which he calls 'invariants', already exist in the real and that all that the perception process does is to home in upon 'them'. A view known as social constructionism (see 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.'

In human communication, according to the theory, a running hypothesis that there is an 'invariant', a target to be homed in upon, is a pragmatic necessity to allow an initial measure of understanding to be established prior to the updating a statement aims to achieve, but it does not and need not represent an actuality. It is added that, after all, it is extremely unlikely that what is desired or feared by an organism will never suffer change—indeed, radical change—as time goes on; the social constructionist theory thus allows for the needful evolutionary adjustment.

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

Perceptual Threshold

One interesting aspect of CNS processing of sensory information is the perceptual threshold, the level of stimulus intensity necessary for you to be aware of a particular sensation. Stimuli bombard your sensory receptors constantly, but your brain can filter out and "turn off" some stimuli. You experience a change in perceptual threshold when you "tune out" the radio whilst studying or when you “zone out” during a lecture. In both cases, the noise is adequate to stimulate sensory neurons in the ear, but neurons higher in the pathway dampen the perceived signal so that it does not reach the conscious brain.Decreased perception of a stimulus is accomplished by inhibitor modulation, which diminishes a suprathreshold stimulus until it is below the perceptual threshold. Inhibitory modulation often occurs in the secondary and higher neurons of a sensory pathway. If the modulated stimulus suddenly becomes important, such as when the professor asks you a question, you can consciously focus your attention and overcome the inhibitory modulation. At that point, your conscious brain seeks to retrieve and recall recent sound input from your subconscious so that you can answer the question.

Theories of perception



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