Apparent spatial arrangement and perceived brightness.

The problems of brightness constancy (e.g., the constancy of perceived object color under different illumination conditions), and of the perceptual constancies in general, arise from the fact that changed sensory stimuli frequently elicit unchanged responses (and vice versa) which follow more closely the variations of distal stimuli (objects) than of the sensory-surface stimulus distributions. This raises difficulties for any formulation of a one-to-one correspondence between stimulus and experience (confusingly called the "constancy hypothesis," [5, p. 86]), which at first sight would seem essential to psychological prediction. Such findings have been used in attempted ("nativistic") refutation of the constancy hypothesis and its associated stimulus-sensation units of analysis (5), and to demonstrate the importance of nonstimulus organizational "forces." Empiricist "inferential" explanations, on the other hand, retain the constancy hypothesis in sensation, and ascribe the obtained discrepancies to the effects of past experience in perception. Objections to the nativistic position are: (a) some evidence suggests that the accuracy of the perceptual constancies depends on past experience (1); (b) no well-defined analytic units have been presented to supplant the old "sensations," and in their absence precise prediction is difficult despite the considerable heuristic value of the more or less intuitive Gestalt "laws." General objections to the empiricist positions have been: (a) it is not possible to distinguish between AND JACOB BECK