Perceptual processes are characterized by a number of dimensions or features: these include stability (the perceptions don’t fluctuate or change, quite the opposite - perceptions can be extraordinarily resistant to change even when the stimulus characteristics are altered); selective attention (the ability to select specific inputs for further processing and exclude others); figure -ground (the apparent superimposition of “object” against “background”); hypothesis testing (finding the “best-fit” interpretation for sensory activity); the impact of contexts (the “settings” of the perceptions) on pre-determining the kinds of hypotheses that will be generated, and the effect of stimulus intensity (how “loud” is a given stimulus, relative to other stimuli) on processing.

While all of these features are contributory, contexts, expectancies and past -experience seem to be among the most important influences determining perceptions.

In order to convincingly argue that something is a perceptual process, there are two criteria which have to be met :- There must be

Variation in experience among people when exposed to a standard stimulus;

Variation within individuals as non-stimulus aspects of the event are changed;

Any phenomenon showing these characteristics is perceptual in nature.