Chapter 8 Flashcards
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.
Attentional capture
Occurs when stimulus salience causes an involuntary shift of attention. For example, attention can be captured by movement.
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. See also point-light walker.
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 of the dots are moving independently; 100 percent coherence means all of the 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 (CDS)
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 by signals that indicate movement of the eyes. See also corollary discharge signal.
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 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.
Image displacement signal (IDS)
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. This local disturbance indicates that the object is moving relative to the environment.
Microstimulation
A procedure in which a small electrode is inserted into the cortex and an electrical current passed through the electrode activates neurons near the tip of the electrode. This procedure has been used to determine how activating 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. See also waterfall illusion.
Motor signal (MS)
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.
Point-light walker
A biological motion stimulus created by placing lights at 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.
Real motion
The physical movement of a stimulus. Contrasts with apparent motion.
Real-motion neuron
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.
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.
Waterfall illusion
An aftereffect of movement that occurs after viewing a stimulus moving in one direction, such as a waterfall. Viewing the waterfall makes other objects appear to move in the opposite direction. See also movement aftereffect.
