Perception of Action Flashcards
who created the ecological theory?
Gibson
summarise the ecological theory
visual info is rich. cog processing and internal representations to make sense of that info not needed. objects perceived as they really are. perception can be explained solely in terms of the environment
background to Gibson’s theory
worked with pilots in WW2. point of focus on runway remained stationary as they flew towards it.
what does optic flow provide detailed information on?
distance (from runaway) and speed
what is optic flow?
expansion/contraction of a scene (an optic tray that reaches the retina). appearance of objects as the observer moves past them
what is gradient of flow?
how much the scene expands on your retina gives you enough information to capture depth perception.
what does gradient of flow say the difference in flow is a function of?
distance from the observer
what is focus of expansion?
point in distance where there is no flow. you don’t need to ‘reconstruct’ the wold to judge where you are going, just use the mechanisms developed to detect FoE.
why does the structure of the optic array change as you move?
different intensities of light shining in different directions during movement; an every changing source of sensory information
how does optic flow differ from other cues?
determined by our own actions
what is affordance?
the ability to discern possibilities for action within the environment
changes in the flow of the optic array contain important information about what?
the type of movement taking place
flaws with Gibson’s ecological theory
head is not often stationary. reductionist (only environment). there is evidence that brain and LTM influences perception. only supports the nature side.
pros of Gibson’s ecological theory
high ecological validity. many applications. good explanation for perception when viewing conditions are clear. highlights richness of info in optic array.
what do Neo-Gibsonians believe and give an example of a researcher?
perceptual and action systems couple to interpret environmental constraints and produce skilled movement. eg. David Lee
example of Neo-Gibsonian research
Land and Lee. measured angle of steering wheel, speed, and direction fo gaze. drivers use other info as well as optic flow to determine their heading such as tangent point
where else do we look, aside from optic flow (bottom-up)?
areas within a scene which have a high proportion of relevant information (top-down)
what does Allport (1989) argue about what features we pay attention to?
we pay attention only to features in the environment that are relevant toward an intended action, thus vision and action are inextricably linked
if you know the size of an object, you can estimate…
its distance
if you note the change in size during approach you can estimate…
speed (the change in distance)
if you know the distance and speed then you can estimate…
the time until you reach the object -TTC
if you know the TTC, then you can…
prepare your behaviour
calculation for TTC
distance to collision/approach speed
what happens to the size of objects travelling toward us?
grow, and vice versa
what happens to the TTC the faster an image is expanding?
the less TTC there is
give an example of good TTC in the real world
fishing gannets - have to streamline wings at just the right moment
what is motion perception used to infer?
self-motion, scene layout, object shape and social intention
give an example of a monocular depth cue
segmentation of foreground from background. motion parallax.
what is motion parallax?
as we move, objects that are closer to use move farther across our field of view than objects in the distance
give an example of a binocular depth cue
compute the distance to various objects. things that are further away slide cross the retina more slowly
what did the point-light walker stimulus study show, and who conducted it?
Johansson (1975). humans are able to perceive human motion and infer a person’s intentions from it.
give an example of an important component related to understanding the intention of a target from body actions
motion smoothness
smoothness of movement often perceived to signal…
an attractive, trustworthy, or competent person
our ability to perceive biological motion may be based on what?
imitation
who demonstrated the existence of ‘mirror neurons’ and in what species?
Gallese et al. (204) in area F5 of monkey premotor cortex
describe a study that provides evidence for mirror neurons in humans
Calvino-Merino et al. (2004). stronger activation in premotor, parietal cortices and STS when expert dancers viewed movement they had been trained to perform and vice versa.
what could be the purposes of mirror neurons?
help imitate the observed action; help understand another animal’s actions and react to them appropriately; link sensory perceptions and motor actions
what can mirror neurons be associated with?
empathy and autism
name 2 impacts of mirror neurones.
injured athletes continue to train without moving a muscle, and can help rehabilitate people whose motor skills have been damaged by stroke
what is the purpose of processing rich visual information?
to safely negotiate a path to our destination
what does dynamic information mean?
environmental information is not static
describe the moving room paradigm
when wall moves forward/backwards: toddlers 12-18 months old fall, adults sway but do not fall. optic flow helps keep balance
what does Patla (1998) argue regulates movement?
feedback control and feed-forward information to plan and adapt movement strategies
what are the 3 requirements for successful walking according to Patla et al?
support the body against gravitational forces; keep the body balanced; adapt to changing environmental demands
to walk around the environment, perceptual information must be integrated with what?
the motor demands required to move the body forward and keep it balanced
summarise evidence for the bottom-up processing argument for perception of movement
Simion et al. (2008) found that new-borns preferred to look at a display showing biological motion (moving chickens) and looked longer at upright displays than inverted ones
summarise evidence fr the top-down processing argument for perception of movement
Thornton et al. (2002); when a point-light display was masked by either a scrambled mask or a random mask, observers found it harder to identify the walker’s direction in the scrambled was condition
summarise evidence for the ecological approach to perception of movement
structural cues: gender differences, men typically have broader shoulders/narrower hips compared to women. dynamic cues: men show relatively grater body sway with upper body compared to women and vice versa
summarise DCD
movement skills below what would be expected given the person’s age and opportunity to practice. daily life significantly affected. prevalence 5-6% of children 5-11 yrs. difficulties handwriting, riding a bike, learning to drive, and negotiating the environment
what are some problems that arise when walking with DCD?
difficulty integrating sensory information while walking (Wilmut et al., 2016); over-reliance on visual information (Smiths-Engelsmna et al. 2003)
how do individuals with DCD walk on level ground?
children: shorter step length, longer in double support. trunk further forward. adults and kids more variable in walking patterns.
how do individuals with DCD walk on uneven ground?
< walking speed, shortened and widened step to a greater extent. inclined their head and trunk more towards the ground
describe the impacts of DCD
cycle of motor skills, self-esteem, participation in physical activity and health in children with DCD (Straker et al., 2011)
