Essay on theories of perception

Describe and Evaluate Top-down and Bottom-Up explanations of perception (24 marks)

Perception is a combination of both the physiological processes involved within the senses and the way in which the brain integrates and interprets the sensory information that it takes in. The two main explanations of perception prioritise the role of one or other of these different aspects.
The bottom-up theory emphasises the importance of stimulus features in perception. The visual information that reaches the eye is thought to contain sufficient unambiguous information about an object for effective perception to take place with little further processing. Gibson suggested that light reaching the eye does so in an optic array. This provides information about such things as distance, movement and meaning. Interpretation is achieved through analysis of the information in the optic array by means of various cues such as texture gradient and horizon ratio. The former refers to the fact that the texture of an object becomes less clear the further it is away. By picking up this information an observer is able to perceive some aspects of depth.
Gibson rejected the view that we perceive a meaningful environment because of the involvement of stored knowledge and experience. He claimed that the meaning of a stimulus is determined by the object’s affordance, ie: the physical structure of an object gives clues as to what its’ potential use. Eysenck and Keane (1990) suggest that the concept of affordances is central to Gibson’s theory as otherwise he would be forced to admit that the meaning of objects is something we store in long-term memory.
Gibson’s theory has provided a good explanation of the generally fast and accurate perception of the environment but it does struggle to explain why we do sometimes make mistakes, as with illusions.
An alternative explanation of perception is that of the top-down approach suggested by Gregory. This sees the eventual product of perception being ‘constructed’, that is, built up from a combination of stimulus information, expectations and hypotheses. The process involves making sense of all the various bits of information provided by the senses. A key aspect of this view of perception is that because of the role of the hypotheses and expectation, perception will be frequently prone to error.