perception

Gestalt psychology

The idea that we naturally organize individual pieces of sensory information into meaningful groups or complete wholes.

Proximity

A Gestalt principle in which objects that are close together are perceived as belonging to the same group.

Similarity

A Gestalt principle in which objects that look similar are perceived as belonging to the same group.

Continuity

A Gestalt principle in which we perceive smooth, continuous patterns instead of separate or sharply changing pieces.

Connectedness

A Gestalt principle in which spots, lines, or areas that are connected are perceived as one unit.

Closure

A Gestalt principle in which we fill in missing gaps to perceive a complete object.

Perceptual constancy

The tendency to perceive an object as unchanged even when the image it produces on the retina changes.

Shape constancy

Perceiving an object as having the same shape even when the viewing angle changes. Example: An open door creates a different retinal image, but we still perceive it as rectangular.

Size constancy

Perceiving an object as having the same size even when its distance changes. Example: A person walking away looks smaller on the retina, but we know the person did not actually shrink.

Color constancy

Perceiving an object's color as mostly unchanged under different lighting. Example: A red apple still appears red in sunlight or indoor lighting.

Brightness constancy

Perceiving an object's brightness as mostly unchanged even when the amount of light on it changes. Example: White paper still appears white in sunlight and in a dim room.

Perceived motion

The brain's interpretation that something is moving, including situations in which stationary images or lights only appear to move.

Stroboscopic effect

The illusion of movement created when a rapid series of slightly different still images is shown. Example: movies, cartoons, or flipbooks.

Phi phenomenon

The illusion that one light is moving when nearby stationary lights flash on and off in sequence. Example: marquee signs or blinking Christmas lights.

Autokinetic effect

The illusion that a stationary point of light is moving when viewed in a dark environment.

Depth perception

The ability to see objects in three dimensions and judge their distance.

Visual cliff experiment

Eleanor Gibson's experiment in which crawling infants usually avoided crawling over an apparent drop covered by glass, showing that babies who are old enough to crawl have developed depth perception.

Two categories of depth cues

Monocular cues and binocular cues.

Monocular cues

Depth cues that can be used with either eye alone.

Linear perspective

A monocular cue in which parallel lines appear to come closer together as they get farther away. Example: railroad tracks seem to meet in the distance.

Interposition

A monocular cue in which an object blocking another object is perceived as closer.

Relative size

A monocular cue in which, if two objects are assumed to be similar in actual size, the object that looks smaller is perceived as farther away.

Texture gradient

A monocular cue in which nearby textures appear detailed and spread out, while distant textures appear smaller and more densely packed.

Shadowing

A monocular cue in which patterns of light and shadow help the brain determine an object's shape, position, and depth.

Motion parallax

A monocular cue in which nearby objects seem to move faster than distant objects as you move. Example: scenery viewed from a moving car or train.

Binocular cues

Depth cues that require both eyes.

Retinal disparity

A binocular cue based on the difference between the images seen by each eye; the greater the difference, the closer the object is.

Convergence

A binocular cue based on how much the eyes turn inward to focus; the more they turn inward, the closer the object is.