chapter 8: perceiving motion

Question 1

define akinetopsia

Answer 1

inability to perceive motion

Question 2

define attentional capture

Answer 2

when our attention is automatically drawn to salient objects

Question 3

define event in the context of perception of movement

Answer 3

segment of time at a particular location that is preserved by observers to have a beginning and an end

Question 4

define event boundary

Answer 4

point in time when each event ends and the next one begins

Question 5

describe the Heider and Simmel’s short animated film experiment

Answer 5

• “house” and three “characters”: circle, small and big triangle
• 2 1/2 min animation film
• Ps created stories based on the movement of the characters and gave them humanlike characteristics and personalities

Question 6

describe the point-light walkers experiment (Centelles, 2013)

Answer 6

• small light placed on people’s joints
• pattern of mov filmed between 2 people
  2 conditions:
• social interaction
• non-social interaction
  Ps could tell just from the joint mov which condition they were watching

Question 7

name the functions of motion perception

Answer 7

• detecting stimuli
• perceiving objects
• understanding events
• social perception
• carrying out physical actions

Question 8

differentiate between real motion and illusory motion

Answer 8

real: when something moves across our field of view
illusory: perception of motion of stimuli that aren’t actually moving

Question 9

name the three types of illusory motion

Answer 9

• apparent motion: two stimuli in slightly different locations are alternated with correct timing
• induced motion: motion of one object causes a nearby stationary object to appear to move
• motion aftereffects: viewing a moving stimulus causes a stationary stimulus to appear to move

Question 10

explain the waterfall illusion

Answer 10

looking at a waterfall for 30-60 seconds then looking off to the side at something that is stationary, everything will appear to move upward for a few seconds

Question 11

explain Larsen’s experiment (2006) and their findings

Answer 11

control condition: 2 squares different positions flashed simultaneously
real motion display: small square move back and forth
apparent motion: squares flashed one after another so that they appeared to move back and forth

finding: activation associated with apparent motion is similar to real motion display activation

Question 12

define optic array

Answer 12

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

Question 13

according to gibson’s ecological approach to motion perception, define local disturbance in the optic array

Answer 13

when portions of the optic array become covered as a person walks by and then are uncovered as they move on

Question 14

define global optic flow

Answer 14

the fact that everything moves at once in response to movement of the observer’s eyes or body

Question 15

name the three signals in the corollary discharge theory

Answer 15

1. image displacement signal: image moves across retina
2. motor signal: sent from the motor area to the eye muscles to cause the eye to move
3. corollary discharge signal: copy of motor signal

Question 16

according to corollary discharge theory, when will movement be perceived?

Answer 16

if comparator (brain structure) receives just one signal, either from image displacement or corollary discharge
- if received both at the same time, no movement perceived

Question 17

explain the reichardt detector

Answer 17

• neuron A sends its signal to output unit
• delay unit slows down signals from A
• during delay, neuron B sends signal down
• if right timing, both arrive at the same time and output unit multiplies responses from A and B = large movement signal results

Question 18

according to the reichardt detector, why isnt a signal created for movement from right to left

Answer 18

• stimulus activates neuron B first which doesn’t have delay unit
• by the time signal from neuron A arrives to output unit, response from B has dropped to 0
• output unit multiplies signal from A and 0 signal from B = no mov signal

Question 19

define coherence

Answer 19

degree to which the dots move in the same direction (Britten 1992)

Question 20

what is the conclusion drawn from newsome’s experiment on the monkeys

Answer 20

linear correlation between coherence and ability to judge direction of motion + firing rate

Question 21

recall what the transcranial magnetic stimulation (TMS) is

Answer 21

temporary disruption of the functioning of a particular brain area by applying a strong magnetic field

Question 22

explain the microstimulation technique

Answer 22

passing weak electrical signal through tip of electrode.
stimulates neurons that are near the electrode tip and causes them to fire

Question 23

what is the medial superior temporal (MST) area responsible for

Answer 23

eye movements, localizing moving object in space

Question 24

define the aperture problem

Answer 24

motion of a one-dimensional structure (bar or edge) cannot be determined unambiguously if it is viewed through a small aperture such as a neuron’s receptive field

Question 25

what are the two solutions to the aperture problem

Answer 25

1. uses info from neurons in the striate cortex that respond to movement of ends of objects
2. uses info from neurons in MT cortex that pool the responses of a number of direcionally selective neurons

Question 26

define the shortest path constraint

Answer 26

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

Question 27

describe shiffrar and freyd’s experiment (1990, 1993)

Answer 27

• when shown two photographs alternating very rapidly, motion would be perceived as a straight line, even if physically impossible
• when alternation slowed down, motion was perceived in a realistic way

Question 28

what was the 2 conclusions drawn from shiffrar and freyd’s experiment

Answer 28

1. visual system needs time to process info in order to perceive movement of complex meaningful stimuli
2. human body might be special and influences the way movement is perceived

Question 29

define biological motion

Answer 29

self-produced motion of a person or other living organism caused by perceptual organization

Question 30

name the functions related to motion associated with each of these brain areas:
- striate cortex (V1)
- middle temporal (MT) area
- medial superior temporal (MST) area
- superior temporal sulcus (STS)

Answer 30

V1: direction of motion across small receptive fields
MT: direction and speed of object motion
MST: processing optic flow, locating moving objects, reaching for moving objects
STS: perception of motion related to animals and people

Question 31

define implied motion

Answer 31

picture that depicts an action involving motion

Question 32

define representational momentum

Answer 32

idea that the motion depicted in a picture tends to continue in the observer’s mind