Goldstein: Sensation and Perception Chapter 8

Akinetopsia

A condition in which damage to an area of the cortex involved in motion perception causes blindness to motion.

Aperture problem

Occurs when only a portion of a moving stimulus can be seen, as when the stimulus is viewed through a narrow aperture. This can result in misleading information about the direction in which the stimulus is moving.

Apparent motion

An illusion of movement that occurs when two objects separated in space are presented rapidly, one after another, separated by a brief time interval.

Biological motion

Motion produced by biological organisms. Most of the experiments on biological motion have used walking humans with lights attached to their joints and limbs as stimuli, so called point-light walkers.

Coherence

In research on movement perception in which arrays of moving dots are used as stimuli, the degree of correlation between the direction of the moving dots. Zero percent coherence means all dots are moving independently, 100% coherence means all dots are moving in the same direction.

Comparator

A structure hypothesized by the corollary discharge theory of movement perception. The corollary discharge signal and the sensory movement signal meet at the comparator to determine whether movement will be perceived.

Corollary discharge signal

A copy of the motor signal that is sent to the eye muscles to cause movement of the eye. The copy is sent to the hypothetical comparator of corollary discharge theory.

Corollary discharge theory

The theory that explains motion perception as being determined both by movement of the image on the retina and signals that indicate movement of the eyes.

Event

A segment of time at a particular location that is perceived by observers to have a beginning and an ending.

Event boundary

The point in time when one event ends and another begins.

Global optic flow

Information for movement that occurs when all the elements in a scene move. The perception of global optic flow indicates that it is the observer that is moving and not the scene.

Illusory motion

Perception of motion when there actually is none. Same as apparent motion/movement.

Image displacement signal

In corollary discharge theory, the signal that occurs when an image moves across the visual receptors.

Implied motion

When a still picture depicts an action that involves motion, so that an observer could potentially extend the action depicted in the picture in his or her mind based on what will most likely happen next.

Induced motion

The illusory movement of one object that is caused by the movement of another object that is nearby.

Local disturbance in the optic array

Occurs when one object moves relative to the environment, so that the stationary background is covered and uncovered by the moving object.

Microstimulation

A procedure in which a small electrode is inserted into the cortex and an electrical current passed through the electrode activates the neurons near the tip of the electrode. This procedure has been used to determine how activation specific groups of neurons affects perception.

Motion aftereffect

An illusion that occurs after a person views a moving stimulus and then sees movement in the opposite direction when viewing a stationary stimulus immediately afterward, e.g. the waterfall illusion.

Motor signal

In corollary discharge theory, the signal that is sent to the eye muscles when the observer moves or tries to move his or her eyes.

Optic array

The structured pattern of light created by the presence of objects, surfaces, and textures in the environment.

Real motion

The physical and actual motion of a stimulus, as opposed to illusory or apparent motion.

Real-motion neuron

A neuron in the cortex that responds when movement of an image across the retina is caused by movement of a stimulus, but does not respond when movement across the retina is caused by movement of the eyes.

Reichardt detector

A neural circuit that results in neurons firing to movement in one direction. Excitation and inhibition are arranged so that movement in one direction creates inhibition that reduces or eliminates neural responding, whereas movement in the opposite direction creates excitation that enhances neural responding.

Representational momentum

Occurs when motion depicted in a still picture continues in an observer's mind.

Shortest path constraint

In the perception of apparent motion, the principle that apparent movement tends to occur along the shortest path between two stimuli.