Lecture 11: Motion

Question 1

What is the principle of attentional capture?

Answer 1

motion attracts attention

Question 2

________________ is a cue that we rely on for distinguishing between event boundaries.

Answer 2

motion

Question 3

What is an example of event boundaries?

Answer 3

changes in speed/acceleration of actor’s hands was a good predictor of subjective judgements about events

Question 4

What is akinetopsia?

Answer 4

inability to perceive motion

Question 5

What is real motion?

Answer 5

occurs when an object is physically moving

Question 6

What is illusory motion (aka apparent movement, phi phenomenon)?

Answer 6

stationary stimuli are presented in slightly differente locations

Question 7

What is induced motion?

Answer 7

movement of one object (usually a larger object like clouds) results in the perception of movement in another object (usually a smaller object like the moon)

Question 8

What is motion aftereffect? What is an example?

Answer 8

observer looks at movement of object for 30-60 seconds, then a stationary object, and movement appears to occur in opposite direction from original movement (e.g. waterfall illusion)

Question 9

Describe the physiology behind motion aftereffect.

Answer 9

• fatiguing/adapting neurons tined to motion in one direction become less sensitive compared to neurons tuned to motion in other directions
• e.g. down neurons fatigued and signals weaken, therefore up neurons generate stronger signals even at baseline

Question 10

In Larsen et al.’s 2006 study comparing real and apparent motion, what were the conditions? What was the major finding?

Answer 10

• control condition: 2 squares in slightly different positions are briefly presented simultaneously
• real motion condition: a small square is moved back and forth
• apparent motion condition: 2 squares are quickly alternated to create illusory motion
• perception of motion in both apparent and real conditions involve SIMILAR NEURAL MECHANISMS

Question 11

When an object moves, but our eyes are stationary, does the image on the retina move? Is object movement perceived?

Answer 11

• image on retina moves
• movement is perceived

Question 12

When an object moves, and our eyes move along with it, does the image on the retina move? Is object movement perceived?

Answer 12

• image on retina is stationary
• movement is perceived

Question 13

When an object is stationary, but our eyes move (e.g. scanning the environment), does the image on the retina move? Is object motion perceived?

Answer 13

• image on retina moves
• movement is NOT perceived

Question 14

What is the ecological approach?

Answer 14

how information directly available in the environment is useful t guide perception/action

Question 15

What does the term optic array refer to?

Answer 15

the structure created by surfaces, textures, and contours in the environment, which change as the observer moves through space

Question 16

Gibson thought the optic array can be used to explain when motion is and isn’t perceived, with reference to which 2 basic kinds of changes?

Answer 16

1. local disturbances in the optic array: objects moving relative to background
2. global optic flow: overall movement of the entire optic array (i.e. without any local disturbances)

Question 17

___________________ may explain why motion is perceived when an object moves whether the eyes are stationery or moving.

Answer 17

local disturbances in the optic array

Question 18

__________________ may explain why motion is NOT perceived when the object is stationary but the eyes are moving.

Answer 18

global optic flow

Question 19

If some aspects of the optic array change, and those changes are not uniform (e.g. some objects are covered/uncovered), will motion be perceived?

Answer 19

yes

Question 20

If the optic array changes in a uniform way (e.g. the entirety of the optic array all moves in exactly the same way), will motion be perceived?

Answer 20

no

Question 21

TRUE or FALSE: According to Gibson, we perceive motion when the entire field moves or remains stationary

Answer 21

FALSE: we perceive motion when one part of the visual scene moves relative to the rest of the scene

Question 22

TRUE or FALSE: According to Gibson, we do not perceive motion when the entire field moves or remains stationary

Answer 22

TRUE

Question 23

What is the corollary discharge theory?

Answer 23

movement perception depends on 3 signals: image displacement signal, motor signal, corollary discharge signal

Question 24

What is the image displacement signal (IDS)?

Answer 24

movement of image stimulating receptors across the retina

Question 25

What is the motor signal (MS)?

Answer 25

signal sent to eyes to move eye muscles

Question 26

What is the corollary discharge signal (CDS)?

Answer 26

derived from the motor signal (i.e. a carbon copy of whatever the motor signal is doing, though it gets sent to a different part of the brain for another purpose)

Question 27

According to the corollary discharge theory, movement is perceived when comparator receives input from ______________________.

Answer 27

either CDS or IDS

Question 28

According to the corollary discharge theory, movement is NOT perceived when comparator receives input ____________________.

Answer 28

at the same time, from both CDS and IDS

Question 29

review last 3 slides for example of how corollary discharge theory applies to motion perception

Answer 29

last 3 slides