Definition (pos): the cognitive processes responsible for analysing sensory information

Summary: Introduction

Errors made in perceptual processes help us to understand how such processes are sophisticated

Perceiving and sensing

The chapter distinguishes between sensation and perception: Sensation refers to the initial detection of the environment, whereas perception refers to the process of constructing a description of the surrounding world, and involves the analysis of sensory information

The eye

Incoming light passes through the cornea into the anterior chamber and then through the lens into the major chamber. The light is focused by the lens/cornea combination on the retina on the back surface of the eye; it is the receptor cells in the retina that sense the light

The retina consists of two broad classes of receptor cells, rods and cones, and both are receptive to light. However, where rods respond better at low light levels, cones are better at high light levels, where they can detect finer detail

Approaches to perception

Psychologists have tried different approaches to studying perception. One distinction between these approaches is whether the ‘goal’ of perception is assumed to be for action or recognition, although the two are not completely separate

Another way of differentiating the approaches is to consider whether the ‘flow’ (processing) of information occurs from the bottom-up or top-down: bottom-up starts with an image formed on the retina by light entering the eye and then analyses and gradually builds up a representation of an object; top-down starts with existing knowledge of the environment, which then guides their processing of sensory information. Both involve building a picture

THE GESTALT APPROACH TO PERCEPTION

Gestalt’s approach was key in the first half of the 20th Century. In perceptual terms, it proposed that an image was perceived according to the organization of elements within it (i.e. perceptual organization), rather than to the nature of individual elements themselves

Examples of perceptual organization are closure (i.e. see images as closed rather than open), good continuation (i.e. generally see images as smooth continuities rather than abrupt changes), proximity and similarity. Such organizational laws are said to be indications of the Law of Pragnanz, and used to group individual components together

GIBSON’S THEORY OF PERCEPTION

Gibson’s bottom-up approach is based on the premise that information in the environment is so rich it does not need processing

Perception and action are strongly linked in Gibson’s approach: action, rather than forming a description of the environment, is the aim of perception. Gibson conceptualized the link by suggesting that perception is direct (i.e. information is sufficiently lit to allow people to interact with the environment), implying that perception of 2D images are indirect

An ecological approach

Gibson believed perception should be studied by determining how real environments structure the light that reaches our retina. This emphasis on real environments, where surfaces are textured, is referred to as an ecological approach to perception. He argued that perception in the real world (which is 3D) is very different to that of 2D environmental stimuli

The optic array and invariant information

Gibson termed the structure that is imposed on light reflected textured surfaces ambient optic array, the basic structure of which is that the reflected light converges where the observer is, so wherever they move so does the optic array

Gibson also argued that additional, higher-order features (i.e. invariants) that could provide unambiguous environmental information existed, and that people could perceive by sampling the optic array (i.e. moving around?) to detect invariant information
Sedgwick (1973) demonstrated that the ‘horizon ratio relation’, where the proportion of an object above and below