Perceptual Constancies




Perceptual constancy denotes the tendency of animals and humans to see familiar objects as having standard shape, size, colour, or location regardless of changes in the angle of perspective, distance, or lighting. The impression tends to conform to the object as it is or is assumed to be, rather than to the actual stimulus. Perceptual constancy is responsible for the ability to identify objects under various conditions, which seem to be "taken into account" during a process of mental reconstitution of the known image.

Even though the retinal image of a receding automobile shrinks in size, the normal, experienced person perceives the size of the object to remain constant. Indeed, one of the most impressive features of perceiving is the tendency of objects to appear stable in the face of their continually changing stimulus features. Though a dinner plate itself does not change, its image on the retina undergoes considerable changes in shape and size as the perceiver and plate move. What is noteworthy is stability in perception despite gross instability in stimulation. Such matches between the object as it is perceived and the object as it is understood to actually exist (regardless of transformations in the energy of stimulation) are called perceptual constancies.size2.gif


1. retrieved January 1, 2009, from http://www.sapdesignguild.org/resources/optical_illusions/images/size2.gif