Chapter 8

Question 1

What is akinetopsia?

Answer 1

Motion is very difficult or impossible to perceive

Question 2

What are the functions of motion perception?

Answer 2

Detecting things
Perceiving objects
Perceiving events
Social perception
Taking action

Question 3

What is an event boundary?

Answer 3

The point in time when each of these events ends and the next one begins

Question 4

What did Zacks find?

Answer 4

Event boundaries are more likely to occur when there is a change in the speed or acceleration of an actor’s hands
The perception of movement plays an important role in separating activities into meaningful events

Question 5

What are point-light walkers?

Answer 5

Created by placing lights on people’s joints and then filming the patterns created by these lights when people move
Observers can see a moving person without any of the other cues that can occur in social situations

Question 6

What is real motion?

Answer 6

When something moves across our field of vision

Question 7

What is illusory motion?

Answer 7

The perception of the motion of stimuli that aren’t actually moving

Question 8

What is apparent motion?

Answer 8

No actual motion between stimuli
The flashing lights example

Question 9

What is induced motion?

Answer 9

Occurs when motion of one object causes a nearby stationary object to appear to move

Question 10

What are motion aftereffects?

Answer 10

Occurs when viewing a moving stimulus causes a stationary stimulus to appear to move

Question 11

What is the waterfall illusion?

Answer 11

If you look at a waterfall for a while and then look off to the side, everything will appear to move upward for a few seconds

Question 12

What is an optic array?

Answer 12

The structure created by the surfaces, textures, and contours of the environment

Question 13

What is a local disturbance in the optic array?

Answer 13

When portions of the optic array become covered as someone walks by and then uncovered when they move on

Question 14

What is global optic flow?

Answer 14

Everything moves at once in response to movement of the observer’s eyes or body
Signals that the environment is stationary and that the observer is moving, either by moving their body or by scanning with their eyes

Question 15

What are the three signals in corollary discharge theory?

Answer 15

Image displacement signal = when an image moves across the retina
Motor signal = sent from the motor area to the eye muscles which causes the eye to move
Corollary discharge signal = copy of the motor signal

Question 16

What is the Reichardt detector?

Answer 16

A circuit that consists of two neurons which send their signals to an output unit that compares the signals it receives

Question 17

What is a delay unit?

Answer 17

The key to the operation of the Reichardt detector circuit
Slows down the signals from neuron A as they travel toward the output unit
It multiplies the responses from A and B to create the movement signal that results in the perception of motion

Question 18

What is the role of the middle temporal area in motion detection?

Answer 18

Contains many directionally selective neurons and is specialized for processing information about motion

Question 19

Where does evidence that the MT cortex is specialized for processing information about motion come from?

Answer 19

From experiments that have used moving dot displays in which the direction of motion of individual dots can be varied

Question 20

What is coherence?

Answer 20

Indicates the degree to which dots move in the same direction
0 = dots moving in random directions
50 = half the dots are moving in the same direction 100 = all dots are moving in the same direction

Question 21

What happens as dot coherence increases?

Answer 21

You are able to judge the direction of motion more accurately
the MT fires more vigorously

Question 22

What happens to coherence when you lesion the MT cortex?

Answer 22

Coherence must be 10 to 20 percent before monkeys can begin detecting the direction of motion

Question 23

What happens when the MT cortex is deactivated using transcranial magnetic stimulation?

Answer 23

Participants had difficult determining the direction in which a random pattern or dots was moving

Question 24

What happens when the MT cortex is stimulated using microstimulation?

Answer 24

Shifts the monkey’s perception of the direction of movement

Question 25

What is microstimulation

Answer 25

Achieved by lowering a small wire electrode into the cortex and passing a weak electrical charge through the tip of the electrode

Question 26

What is the aperture problem?

Answer 26

The neurons’ receptive field functions like an aperture, only revealing small portions of a scene

Question 27

What are some solutions to the aperture problem?

Answer 27

Neurons can use information from the end of a moving object to determine its direction of motion (striate cortex)
Combining responses from a number of neurons (MT cortex)

Question 28

What is the shortest path constraint?

Answer 28

Apparent movement tends to occur along the shortest path between two stimuli

Question 29

What is biological motion?

Answer 29

Self-produced motion of a person or other living organisms

Question 30

Why are we good at seeing biological motion?

Answer 30

Because we see it all of the time

Question 31

What area in the brain is activated by biological motion?

Answer 31

A small area in the superior temporal sulcus
Also the FFA and the PFC that contain mirror neurons

Question 32

What is implied motion?

Answer 32

When an image depicts an action involving motion

Question 33

What is representational momentum?

Answer 33

The idea that the motion depicted in a picture tends to continue in the observer’s mind
Example of experience influencing perception