week 7 - motion perception

Question 1

akinetopsia

Answer 1

blindness to motion

Question 2

Heider and Simmel experiment (animated shapes)

Answer 2

• subjects watched a film of animated shapes that acted as characters and interacted with each other
• subjects were then asked to describe what was occurring

Question 3

What were the results of the Heider and Simmel experiment?

Answer 3

despite not being people, subjects were able to create stories explaining the actions of the different objects and even gave them human like characteristics/personalities

Question 4

attentional capture

Answer 4

• motion attracts attention to the moving object
• ex.) waving arm to attract the attention of someone across the room

Question 5

real motion

Answer 5

object is physically moving

Question 6

illusory motion

Answer 6

Arises when an observer looks at an object for a long period of time and looks at a stationary stimulus. The stationery stimulus then appears to be moving

Question 7

apparent motion

Answer 7

• stationary stimuli are presented in slightly different locations
• basis of movement in moves and TV

Question 8

apparent movement experiment

Answer 8

• Experiment containing two light sources in slightly different locations. One light turns on, followed by a period of darkness, and then the other light turns on
• One would perceive that a single light is moving from on area to the other

Question 9

induced motion

Answer 9

• movement of one object results in the perception of movement in another object
• ex.) movement of clouds creates the illusion that the moon is moving

Question 10

motion aftereffect experiment

Answer 10

• Observer looks at movement of object for 30-60 seconds
• Observer then looks at stationary object
• Movement appears to occur in the opposite direction from original movement

Question 11

Larsen experiment (light dots)

Answer 11

• participants scanned by fMRI while viewing 3 displays
• control condition: two dots in different positions are flashed simultaneously
• real motion: a small dot is moved back and forth
• apparent motion: dots are flashed so they appear to move

Question 12

What were the results of the Larsen experiment?

Answer 12

• two areas are overlapping, they activate the same different neural regions
• control condition: each dot activated a separate area of the visual cortex
• apparent and real motion: activation of visual cortex from both sets of stimuli was similar; thus the perception of motion in both cases is related to the same brain mechanism

Question 13

an object moves and the observer is stationary…

Answer 13

movement creates an image that moves on the observer’s retina

Question 14

an object moves and the observer follows the object with their eyes…

Answer 14

movement is tracked so that the image is stationary on the retina

Question 15

an observer moves through a stationary environment…

Answer 15

image of environment moves across retina but environment is perceived as stationary

Question 16

motion perception

Answer 16

information in the environment

Question 17

ecological approach (gibson)

Answer 17

• information is directly available in the environment for perception
• ex.) optic array

Question 18

optic array

Answer 18

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

Question 19

local disturbance in the optic array

Answer 19

objects relative to background such that is covered and uncovered

Question 20

global optic flow

Answer 20

• overall movement of optic array
• indicates that the observer is moving and not the environment

Question 21

reichardt detectors

Answer 21

• neurons that fire to movement in one direction
• excitation and inhibition are arranged so that movement in one direction creates inhibition that eliminates neural responding

Question 22

describe the movement of reichardt detectors inhibiting neural response

Answer 22

1. A is excited by light
2. A excites E
3. E inhibits F
4. light excites B but it is too late to excite
5. neural response is eliminated

Question 23

describe the movement of reichardt detectors exciting neural response

Answer 23

1. Receptor D is excited by light
2. D activates H
3. neural response is activated
4. Light reaches receptor C
5. C excites G and attempts to inhibit H but it has already been excited

Question 24

corollary discharge theory

Answer 24

movement perception depends on 3 signals: 1. image displacement signal 2. motor signal 3. corollary discharge signal

Question 25

image displacement signal

Answer 25

movement of image stimulating receptors across the retina

Question 26

motor signal

Answer 26

signal sent to eyes to move muscles

Question 27

corollary discharge signal

Answer 27

split from motor signal; copy of motor signal sent to different area of brain

Question 28

What are the physiological evidence for the corollary discharge theory?

Answer 28

• damage to medial superior temporal area in humans lead to perception of movement of stationary environment with the movement of eyes
• real-movement neurons found in monkeys that respond only when a stimulus moves and do not respond when eyes move

Question 29

Newsome experiment (firing and dot coherence)

Answer 29

• coherence of movement of dot patterns was varied
• monkeys were taught to judge direction of dot movements and measurements were taken from MT neurons

Question 30

What were the results of the Newsome experiment?

Answer 30

as coherence of dot movement increased, so did the firing of the MT neurons and the judgment of movement accuracy

Question 31

Newsome and Pare (monkey lesioning)

Answer 31

• normal monkeys can detect motion with coherence of 1 or 2%
• monkeys with lesions in MT cortex cannot detect motion until coherence is 10-20%

Question 32

Movshon and Newsome (microstimulation)

Answer 32

• monkey trained to indicate direction of moving dots
• neurons inMT cortex that respond to specific direction were activated
• microstimulation of different direction sensitive neurons

Question 33

What were the results of Movshon and Newsome?

Answer 33

monkey shifted judgment to the artificially stimulated direction

Question 34

complex cortical cell

Answer 34

respond preferentially to an oriented bar moving in a specific direction

Question 35

aperture problem

Answer 35

observation of small portion of larger stimulus leads to misleading information about direction of movement

Question 36

biological motion

Answer 36

movement of person or other living organism

Question 37

Grossman and Blake experiment (point-light)

Answer 37

• Participants viewed point-light stimuli for activities
• Task was to determine whether motion was biological or scrambled
  Noise was added to dots so they could only achieve 71% accuracy

Question 38

What occurred in the Grossman and Blake experiment when TMS was applied to STS?

Answer 38

• Transcranial magnetic stimulation applied to STS caused a decrease in ability to detect biological motion
• Suggests that STS is helpful for perceiving biological motion

Question 39

implied motion

Answer 39

still pictures that depict an action that involves motion

Question 40

jumping over wall (implied motion)

Answer 40

• We have difficulty differentiating two still motion pictures going forward in time because our brain automatically perceives the motion occurring
• However, it is much easier to detect the still motion picture going backwards

Question 41

representational momentum

Answer 41

observers show that the implied motion is carried out in the observer’s mind

Question 42

Kourtzi and Kanwisher experiment

Answer 42

fMRI response was measured in MT and MST to pictures with
- Implied motion
- No-implied motion
- At rest
- Houses

Question 43

What were the results of the Kourtzi and Kanwisher experiment?

Answer 43

Results showed areas of brain responsible for motion fire in response to pictures of implied motion