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 erceive 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 ut 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.