Topic 7: Perception and Action Flashcards
Ecological Approach to Perception
this approach focuses on specifying the information in the environment that is used for perception, emphasizing the study of moving observers to determine how their movements results in perceptual information that both creates perception and guides further movement
Optic Flow
the flow of stimuli in the environment that occurs when an observer moves relative to the environment
forward movement causes an expanding optic flow, whereas backward movement causes a contracting optic flow
some researchers use the term optic flow field to refer to this flow
Gradient of Flow
in an optic flow pattern, a gradient is created by movement of an observer through the environment
the “gradient” refers to the fact that the optic flow is rapid in the foreground and becomes slower as distance from the observer increases
Focus of Expansion (FOE)
the point in the flow pattern caused by observer movement in which there is no expansion
according to J.J. Gibson, the focus of expansion always remains centered on the observer’s destination
Invariant Information
environmental properties that do not change as the observer moves relative to an object or scene
for example, the spacing, or texture, of the elements in a homogenous texture gradient does not change as the observer moves on the gradient
the texture of the gradient therefore supplies information for depth perception
Affordances
the information specified by a stimulus patter that indicates how the stimulus can be used
an example of an affordance would be seeing a chair as something to sit on or a flight of stairs as something to climb
Action Affordances
a response to an object that involves both its affordance (what it is for) and the action associated with it
Visual Direction Strategy
a strategy used by moving observers to reach a destination by keeping their body oriented toward the target
Spatial Updating
process by which people and animals keep track of their position within a surrounding environment when they move
Wayfinding
the process of navigating through the environment
wayfinding involves perceiving objects in the environment, remembering objects and their relation to the overall scene, and knowing when to turn and in what direction
Landmarks
object on a route that serves as a cue to indicate where to turn
a source of information for wayfinding
Cognitive Map
a mental map of the spatial layout of an area of the environment
Place Cells
neurons that fire only when an animal is in a certain place in the environment
Place Field
area of the environment within which a place cell fires
Grid Cells
cells in the entorhinal cortex that fire when an animal is in a particular place in the environment, and which have multiple place field arranged in a grid-like pattern
Parietal Reach Region (PRR)
network of areas in the parietal cortex that contains neurons that are involved in reaching behavior
Visuomotor Grip Cells
a neuron that initially responds when a specific object is seen and then also responds as a hand grasps the same object
Proprioception
the sensing of the position of the limbs
Size-Weight Illusion
erroneously predicting weight when observing two differently sized objects that have the same weight
the error occurs when the perceiver predicts that the larger object will be heavier, and therefore uses more force to lift it, causing it to be lifted higher and to feel lighter
Audiovisual Mirror Neurons
neuron that responds to actions that produce sounds
these neurons respond when a monkey performs a hand action and when it hears the sound associated with this action
Mirror Neuron System
network of neurons hypothesized to play a role in creating mirror neurons
Action-Specific Perception Hypothesis
hypothesis that people perceive their environment in terms of their ability to act on it
What are the assumptions made in the ecological approach?
emphasized evolution: natural selection has shaped our perceptual system, considered perception in the natural environment, understanding motion of observer is important
all info required for perception is available in environment (bottom-up): optic array (stimulus pattern in the environment) is highly organized
the visual scene is analyzed in terms of whole objects and surfaces, not edges, colors, etc. that comprise objects: certain characteristics of the environment are invariant: a particular relationship holds constant
perception is direct, immediate: do not require further computation/mental operations, or additional info based on inferences or experience, no top-down processing
What is optic flow?
stimulus array changes in a logical way as observer moves through the environment
What was the Lee & Reddish (1976) research example of the ecological approach?
analyzed diving behavior of gannets
tau: ratio of target’s retinal size at two different times divided by the rate of change of its retinal size over time (i.e., time to impact)
note tau is independent of object distance or observer velocity; it is an invariant; based on optic flow
gannets always retract their wings right before hitting surface of the water, regardless of initial height, indicating sensitivity to time to collision (tau?)
How is object perception functional?
affordances: actions one can perform with an object
e.g., tree is for climbing, chopping, hugging, not eating
e.g., atmosphere affords visual, auditory, & olfactory perception
What are the pros and cons of the ecological approach?
pros: identifying invariants adds to understanding
cons: perceptual processing exists; is important
What is the lateral IP area?
represents location you plan to move your eyes to (“saccade planning area”)
What is the medial IP area?
represents area one can reach to
responds to visual and somatosensory input (“parietal reach region”)
What is the ventral IP area?
responds to moving nearby visual input/tactile input to face
important for feeding behavior
What is the anterior IP area?
represents important shape information for grasping objects
located between sensory and motor areas
contains neurons that respond to visual stimuli and physical action
nearby neurons (in intraparietal sulcus) implicated in cognitive functins that require integration of sensory and motor information (e.g., movement planning, spatial attention, and decision-making)
sends projections to premotor cortex and then to motor cortex
What are the types of AIP neurons?
motor-dominant
visual-dominant
visual and motor
What are motor dominant AIP neurons?
respond when action performed in the dark or in the light, but not to seeing visual cue
What are visual dominant AIP neurons?
respond when action performed in the light, but not in the dark
What are visual and motor AIP neurons?
respond to action in the light, and to a lesser degree to action in teh dark, or to visual cue alone
How were mirror neurons discovered?
probed premotor cortex (area F5) in brain of macaque monkeys
neurons responded when monkeys grasped a piece of food
by coincidence, one researcher reached for a banana, and some of the neurons reacted
What are mirror neurons?
activated when a goal-directed action is performed, and when a similar action is observed
found for grasping, manipulating, or placing objects
What are the features of mirror neurons?
require biological motion: no response if object picked up with pliers
seems to be an execution-observation matching system (e.g., mirror neurons active as novice guitarists watched a professional play chords)
no response when action observed without object
no response to mere visual presentation of objects
audio-visual mirror neurons can be triggered by visual information and by the sound of a particular action
mirror neurons infer the goal of an observed action
mirror neuron activation dependent on understanding intentions; intentions transcend the context of an action; they require comprehension of the “hypergoal”
What was the research by Ramachandran (1996) on mirror neurons in humans?
patients with a right-hemisphere stroke have paralysis of the left side of their body; about 5% of patients deny their paralysis (“denial syndrome” or anosognosia) and that of other patients too
some evidence suggests Broca’s area (speech production) in humans is comparable to F5 in monkeys
activation found in areas of the human premotor cortex when: reading literal phrase, watching a video of fruit being bitten or a pen being grasped, but not by a metaphorical phase
What was the research by Saygin et al. (2012) on biological motion and mirror neurons?
fMRI brain scans taken of observers watching video of recognizable actions by: a person, an android, a robot endoskeleton
less activity in anterior intraparietal sulcus when viewing robot endoskeleton
activity may be due to mirror neuron system
What role have mirror neurons played in evolution?
changes in human development over time are not due simply to increases in brain size, or unaccounted evolutionary changes
mirror neurons may account for rapid spread of innovations (“see one, do one, teach one”)
mirror neurons may simply have become activated by environmental triggers, causing the so-called big bang; perhaps due to an increase in “learnability”
mirror neurons are necessary, but not sufficient for advances to occur
