Perceptual Constancy examines a group of long-standing problems in the field of perception and provides a review of the fundamentals of the problems and their solutions. Experts in several different fields - including computational vision, physiology, neuropsychology, psychophysics and comparative psychology - present their approaches to one of the fundamental problems of perception: How does the brain extract a stable world from an ever-changing retinal input? How do we achieve color constancy despite changes in the wavelength content of daylight? How do we recognize objects from different viewpoints? And how do we know the sizes of those objects? The volume is divided into three sections, each of which addresses developmental, clinical and comparative issues, psychophysics, and physiology. The first section is on color constancy, the second section describes size, shape and speed, and the third is on perceptual inconstancies. The final chapters address how the visual system must retain the ability to learn and also how the errors we make reveal the mechanisms we use.