Perceptual Constancy

Perceptual constancy is the tendency to perceive an object's size, shape, color, or brightness as stable even as the raw sensory information reaching the eye changes with distance, viewing angle, or lighting. A door swinging open, for instance, projects a rapidly changing trapezoidal image onto the retina, yet is still perceived as a constant rectangular shape, and a piece of coal in bright sunlight is still seen as black even though it may physically reflect more light than a white object seen indoors. The phenomenon covers several related constancies, including size, shape, color, and brightness constancy, and is understood as the visual system correcting raw sensory data using contextual cues rather than reporting it unprocessed.