chapter 8: perceiving motion Flashcards
define akinetopsia
inability to perceive motion
define attentional capture
when our attention is automatically drawn to salient objects
define event in the context of perception of movement
segment of time at a particular location that is preserved by observers to have a beginning and an end
define event boundary
point in time when each event ends and the next one begins
describe the Heider and Simmel’s short animated film experiment
- “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
describe the point-light walkers experiment (Centelles, 2013)
- 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
name the functions of motion perception
- detecting stimuli
- perceiving objects
- understanding events
- social perception
- carrying out physical actions
differentiate between real motion and illusory motion
real: when something moves across our field of view
illusory: perception of motion of stimuli that aren’t actually moving
name the three types of illusory motion
- 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
explain the waterfall illusion
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
explain Larsen’s experiment (2006) and their findings
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
define optic array
structure created by the surfaces, textures and contours of the environment
according to gibson’s ecological approach to motion perception, define local disturbance in the optic array
when portions of the optic array become covered as a person walks by and then are uncovered as they move on
define global optic flow
the fact that everything moves at once in response to movement of the observer’s eyes or body
name the three signals in the corollary discharge theory
- image displacement signal: image moves across retina
- motor signal: sent from the motor area to the eye muscles to cause the eye to move
- corollary discharge signal: copy of motor signal
according to corollary discharge theory, when will movement be perceived?
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
explain the reichardt detector
- 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
according to the reichardt detector, why isnt a signal created for movement from right to left
- 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
define coherence
degree to which the dots move in the same direction (Britten 1992)
what is the conclusion drawn from newsome’s experiment on the monkeys
linear correlation between coherence and ability to judge direction of motion + firing rate
recall what the transcranial magnetic stimulation (TMS) is
temporary disruption of the functioning of a particular brain area by applying a strong magnetic field
explain the microstimulation technique
passing weak electrical signal through tip of electrode.
stimulates neurons that are near the electrode tip and causes them to fire
what is the medial superior temporal (MST) area responsible for
eye movements, localizing moving object in space
define the aperture problem
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
what are the two solutions to the aperture problem
- uses info from neurons in the striate cortex that respond to movement of ends of objects
- uses info from neurons in MT cortex that pool the responses of a number of direcionally selective neurons
define the shortest path constraint
apparent movement tends to occur along the shortest path between two stimuli
describe shiffrar and freyd’s experiment (1990, 1993)
- 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
what was the 2 conclusions drawn from shiffrar and freyd’s experiment
- visual system needs time to process info in order to perceive movement of complex meaningful stimuli
- human body might be special and influences the way movement is perceived
define biological motion
self-produced motion of a person or other living organism caused by perceptual organization
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)
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
define implied motion
picture that depicts an action involving motion
define representational momentum
idea that the motion depicted in a picture tends to continue in the observer’s mind
