Chapter 8: Perceiving Motion Flashcards
What are the 3 functions of movement perception?
- Understanding events: movement of objects assist in organization of stimuli
- Attracting attention: important for survival if predator
- Information about objects: ambiguous objects could be misinterpreted without movement of objects or observer
What is Akinetopsia?
Motion agnosia; damage to cortex resulting in an inability to perceive movement
What is Attentional Capture?
Motion attracts attention to the moving object
What are 4 ways to perceive motion?
- Real motion
- Illusionary motion: basis of movement in movies
- ex, apparent motion - Induced motion: movement of one object causes perceived movement of another
- ex, moon moving behind the clouds - Motion Aftereffect: looking at a moving stimulus 30-60secs then stationary object looked at will be perceived to be moving in opposite direction
- ex, waterfall
Explain Larson’s experiment involving real vs apparent motion
3 conditions:
- Control condition: 2 dots flashing simultaneously
- Real motion: 1 dot moving
- Apparent motion: 2 dots flashed to appear as if moving
- Result: (1) activated separate areas of visual cortex
- Result: (2) and (3) activated similar areas
- Finding: perception of motion is related to the same brain mechanisms
What are the 3 conditions of motion perception?
- Object moves, observer is stationary: creates moving image on retina
- Object moves, observer’s eyes follow: stationary image on the retina
- Observer moves through stationary environment: moving image on retina but environment is perceived as stationary
What are the 2 explanations for motion perception?
- Ecological approach: info is available in the environment for perception
- Physiological approach: neural processing
Define Local Disturbances
Disruptions in the optic array by covering/uncovering the background in part
Define Global Optic Flow
Overall movement of optic array indicating that an observer is moving, not the environment
What is the Reichardt Detector?
A neural network that encodes motion
When receptors are stimulated right to left, neuron fires
Explain the Corollary Discharge Theory
Movement perception depends on 3 things:
- Motor signal (MS): signal sent to move eye muscles
- Corollary discharge signal (CDS): split of an MS
- Image displacement signal (IDS): movement of image stimulating receptors across the retina
- Movement is perceived when Comparator receives input from either CDS or IDS BUT NOT BOTH
(Explains why environment perceived as stationary when observer moves through stationary environment)
What are 2 pieces of evidence that support the corollary discharge theory?
- Damage to MST leads to perception of movement of stationary environment
- Patient R.W.: damaged MST, IDS was created by eye movements
- Real-Movement Neurons: in monkeys, respond only when a stimulus moves and not when eyes move