Sensation And Perception Ch.9

Front 1

Aperture problem

Back 1

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

Front 2

Apparent movement (or stroboscopic movement)

Back 2

An illusion of movement that occurs between two objects separated in space when the objects are flashed rapidly on and off, one after another, separated by a brief time interval.

Front 3

Biological motion

Back 3

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. See also Point-light walkers.

Front 4

Coherence

Back 4

A term used to describe the degree of correlation between the direction of moving objects. In displays containing many moving dots, zero percent coherence means all of the dots are moving independently; 100 percent coherence means all of the dots are moving in the same direction.

Front 5

Comparator

Back 5

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.

Front 6

Corollary discharge signal (CDS)

Back 6

A copy of the signal sent from the motor area of the brain to the eye muscles. The corollary discharge signal is sent to the hypothetical comparator of corollary discharge theory.

Front 7

Corollary discharge theory

Back 7

According to this theory of motion perception, a corollary discharge signal, which is a copy of the signal sent from the motor area to initiate an eye movement, is sent to a structure called the comparator. At the comparator, information in the corollary discharge is compared to the sensory movement signal. If the corollary discharge signal and the sensory movement signal do not cancel each other, movement is perceived.

Front 8

Global optic flow

Back 8

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

Front 9

Image movement signal (IMS)

Back 9

In corollary discharge theory, the signal that occurs when an image stimulates the receptors by moving across them.

Front 10

Implied motion

Back 10

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.

Front 11

Induced movement

Back 11

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

Front 12

Kinetic depth effect

Back 12

Occurs when a stimulus’s three-dimensional structure becomes apparent from viewing a two-dimensional image of a stimulus as it rotates. See also Structure-from-motion.

Front 13

Local disturbance in the optic array

Back 13

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

Front 14

Microstimulation

Back 14

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

Front 15

Motion agnosia

Back 15

An effect of brain damage in which the ability to perceive motion is disrupted.

Front 16

Motor signal (MS)

Back 16

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.

Front 17

Movement aftereffect

Back 17

An illusion that occurs after a person views a moving stimulus and then sees movement in the opposite direction when viewing a stationary stimulus. See also Waterfall illusion.

Front 18

Occlusion heuristic

Back 18

The assumption that a moving object will cover and uncover the background and that when the background is covered, it still exists. Thus, when a large object is occluded by a smaller one, we see the larger one as continuing to exist behind the occluder.

Front 19

Optic array

Back 19

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

Front 20

Point-light walker

Back 20

A biological motion stimulus created by placing lights on a number of places on a person’s body and having an observer view the moving-light stimulus that results as the person moves in the dark.

Front 21

Real movement

Back 21

The physical movement of a stimulus.

Front 22

Real-movement neuron

Back 22

Neuron in the monkey’s 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.

Front 23

Representational momentum

Back 23

Occurs when an observer views two pictures depicting the same motion, one after another, and is asked to indicate whether the second picture is the same as or different from the first picture. Representational momentum occurs when the second picture depicts the action later in time but is identified by the observer as being identical to the first picture.

Front 24

Shortest-path constraint

Back 24

The principle that apparent movement occurs along the shortest path between two stimuli when they are flashed on and off with the appropriate timing.

Front 25

Structure-from-motion

Back 25

A situation in which movement of a stimulus creates the perception of an object that was not perceived when the stimulus was stationary. See also Kinetic depth effect.

Front 26

Waterfall illusion

Back 26

An aftereffect of movement that occurs after viewing a stimulus moving in one direction, such as a waterfall. Viewing the waterfall creates other objects to appear to move in the opposite direction.