Perception and knowledge

Knowledge concerning the object, scene, or event in a conscious propositional form generally does not affect perception. By and large, perception is autonomous with respect to thought. That is because perception is stimulus bound and is based on mental contents, lawful principles and rules that are unconscious and in a form very different from such consciously represented propositional knowledge. Exceptions to this generalization can occur if the stimulus is ambiguous and can support a cued or suggested interpretation or one in line with what is known to be present as well as it can support the perception that occurs spontaneously. How the representation of the given, consciously apprehended knowledge can enter into the unconscious events that govern perception is not known, but it is suggested that such knowledge accesses memories and it is these memories that can affect perception.Since knowledge of this kind can affect perception, it is important to ensure that subjects in experiments are naive. Otherwise we will confuse spontaneous perceptions with those that only occur when suggested and the distinction is theoretically important. In certain cases, knowledge leads to an intentional intervention in the process of achieving a percept, the mechanism of which is not known. However, this kind of effect may be based on a process of imagining or visualizing of objects or events that dovetails with the proximal stimulus and it is the imagining that leads to the perception.Knowledge in the form of stored representations of past visual experience (or of phylogenetic ‘experience’) can affect perception in various ways: it enables recognition and interpretation to occur; it enables perceptual discrimination among similar members of a category to occur; it can lead to perceptual enrichment effects; it provides internal solutions which can then be accessed in cases where perceptual problem solving occurs; it provides rules or laws concerning geometrical optics on the basis of which phenomena such as perceptual constancy and the like can be achieved; it can lead to the recalibration of tactual or visual sensation. However, before such top-down effects of past experience can occur bottom-up processes must first achieve a preliminary perception. That perception provides the bridge to the relevant stored representations which are accessed on the basis of similarity.