The status of the minimum principle in the theoretical analysis of visual perception.

We examine a number of investigations of perceptual economy or, more specifically, of minimum tendencies and minimum principles in the visual perception of form, depth, and motion. A minimum tendency is a psychophysical finding that perception tends toward simplicity, as measured in accordance with a specified metric. A minimum principle is a theoretical construct imputed to the visual system to explain minimum tendencies. After examining a number of studies of perceptual economy, we embark on a systematic analysis of this notion. We examine the notion that simple perceptual representations must be defined within the "geometric constraints " provided by proximal stimulation. We then take up metrics of simplicity. Any study of perceptual economy must use a metric of simplicity; the choice of metric may be seen as a matter of convention, or it may have deep theoretical and empirical implications. We evaluate several answers to the question of why the visual system might favor economical representations. Finally, we examine several accounts of the process for achieving perceptual economy, concluding that those which favor massively parallel processing are the most plausible. The notions of "simplicity " and "economy" have been used in varied contexts within the sciences (see Sober, 1975). It was a commonplace of classical physics and astronomy that "nature acts by the simplest means. " Euler, Lagrange, Hamilton, and others have shown that the central equations of mechanics can be formulated isoperimetrically (in terms of maximum/minimum solutions). In a broader vein, methodologists have proposed that scientists proceed in accordance with the principle of parsimony, which holds that of two theories with equal empirical adequacy, the simpler theory should be chosen. A century ago Mach (1883/1960, 1919) referred this principle to a psychological preference of the scientific investigator for economy of thought. Finally, psychologists have found a tendency