Word frequency, personal values, and visual duration thresholds.

If a psychologist is asked how a "perception" can be observed, he will usually reply that we really observe a verbal report or some other overt response taking place in the presence of certain stimulus patterns. Such an acknowledgment is what often passes for an "operational definition" of perception. Actually such apparent scientific sophistication has not always been significant within the psychology of perception. It is so easy to say that one could make such an operational definition if one really wanted to, that much of the literature on perception remains without specified operational definition of concepts. Perceptual processes like "seeing," "distorting," and "selecting," are concepts which are still used incorrectly in the psychology of perception. Such concepts often are private and inprecise, although presumably they need not be; and they often admit ad hoc explanations of certain observed relations between responses and stimuli. In the recent literature on perception, for example, we find statements such as the following: "A perception is an experience of something" (2, p. 14). "What one sees, what one observes, is inevitably what one selects from a near infinitude of potential percepts" (9, p. 142). "The goal of perception, in its broadest sense,