Chapter 8 Vocab

Question 1

akinetopsia

Answer 1

A rare neuropsychological disorder in which the affected individual has no perception of motion.

Question 2

aperture problem

Answer 2

The fact that when a moving object is viewed through an aperture (or a receptive field), the direction of motion of a local feature or part of the object may be ambiguous.

Question 3

aperture

Answer 3

An opening that allows only a partial view of an object.

Question 4

apparent motion

Answer 4

The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession.

Question 5

biological motion

Answer 5

The pattern of movement of living beings (humans and animals).

Question 6

comparator

Answer 6

An area of the visual system that receives one copy of the command issued by the motor system when the eyes move (the other copy goes to the eye muscles). The comparator compares the image motion signal with the eye motion signal and can compensate for the image changes caused by the eye movement.

Question 7

correspondence problem

Answer 7

In motion detection, the problem faced by the motion detection system of knowing which feature in frame 2 corresponds to a particular feature in frame 1.

Question 8

first-order motion

Answer 8

The motion of an object that is defined by changes in luminance.

Question 9

focus of expansion

Answer 9

The point in the center of the horizon from which, when we’re in motion (e.g., driving on the highway), all points in the perspective image seem to emanate. The focus of expansion is one aspect of optic flow.

Question 10

interocular transfer

Answer 10

The transfer of an effect (such as adaptation) from one eye to the other.

Question 11

luminance-defined object

Answer 11

An object that is delineated by changes in reflected light.

Question 12

microsaccade

Answer 12

An involuntary, small, jerklike eye movement.

Question 13

middle temporal area (MT)

Answer 13

An area of the brain thought to be important in the perception of motion.

Question 14

motion aftereffect (MAE)

Answer 14

The illusion of motion of a stationary object that occurs after prolonged exposure to a moving object.

Question 15

optic array

Answer 15

The collection of light rays that interact with objects in the world that are in front of a viewer. Term coined by J. J. Gibson.

Question 16

optic flow

Answer 16

The changing angular positions of points in a perspective image that we experience as we move through the world.

Question 17

reflexive eye movement

Answer 17

A movement of the eye that is automatic and involuntary.

Question 18

saccade

Answer 18

A type of eye movement, made both voluntarily and involuntarily, in which the eyes rapidly change fixation from one object or location to another.

Question 19

saccadic suppression

Answer 19

The reduction of visual sensitivity that occurs when we make saccadic eye movements. Saccadic suppression eliminates the smear from retinal image motion during an eye movement.

Question 20

second-order motion

Answer 20

The motion of an object that is defined by changes in contrast or texture, but not by luminance.

Question 21

smooth pursuit

Answer 21

A type of voluntary eye movement in which the eyes move smoothly to follow a moving object.

Question 22

superior colliculus

Answer 22

A structure in the midbrain that is important in initiating and guiding eye movements.

Question 23

tau (τ)

Answer 23

Information in the optic flow that could signal time to collision (TTC) without the necessity of estimating either absolute distances or rates. The ratio of the retinal image size at any moment to the rate at which the image is expanding is tau, and TTC is proportional to tau.

Question 24

texture-defined (contrast-defined) object

Answer 24

An object that is defined by changes in contrast, or texture, but not by luminance.

Question 25

time to collision (TTC)

Answer 25

The time required for a moving object (such as a cricket ball) to hit a stationary object (such as a batsman’s head). TTC = distance/rate.

Question 26

vergence

Answer 26

A type of eye movement in which the two eyes move in opposite directions; for example, both eyes turn toward the nose (convergence) or away from the nose (divergence).