Perception, motion and action- Lecture 2 Flashcards

1
Q
James Gibson (1904-1979)
Theory of direct perception
A

The perceived environment is not a construct of the brain- information is picked up from the environment and processed in a one way system
accounts
for recognition of objects, their position in the space, their movement and direction and their
relation to the observer. T

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2
Q

Affordances

Important concept in Gibson’s theory (1979)

A

an object is perceived not only by its visual features, but also by the potential
motor actions it affords

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3
Q

Pappas & Mack (2008)

A

Unseen objects that afford motor response activate the visuomotor system automatically without conscious perception- THE AFFORDANCE EFFECT

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4
Q

Will et al (2013)

A

affordance of graspability triggers rapid activity in the motor cortex (compatible images would be able to grasp-correct orientated object)

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5
Q

Visually guided action-
Optic flow
Gibson (1950)

A

How the objects and surfaces in the environment flow when you move through the world- due to changes in the pattern of light that reaches the eyes of the observer

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6
Q

Focus of expansion

A

Target point towards which the observer is moving towards- appears to be motionless

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7
Q

Smith et al (2006)

A

Medial superior temporal area is strongly responsive to coherent optic flow- fMRI shows high activity in MST area to moving

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8
Q

Optic array

A

is all the information
from the environment that reaches the eyes
It is subjective- depends on our position and orientation in the environment

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9
Q

Flaw in Affordances

A

Oversimplified, as the same object may have a range of affordances- actually learning, practise, mood, psychological state and creativity may influence the perceived use- no longer bottom up approach

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10
Q

Invariant

A

higher order of the opric array that remains unaltered as observers move around the environment
e.g. focus of expansion, texture gradients, parallel lines that converge to a point

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11
Q

Flaw in Gibsons notion of Optic flow

A

If we can’t move directly to our goal then things become more complicated

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12
Q

Retinal Flow field

A

it is the changes in the pattern of light that reaches the retina produced by the
observer moving in environment as well as eye and head movements
Linear Retinal Flow + Rotary Retinal Flow.

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13
Q

Linear Retinal Flow

A

contains a focus of expansion (= optic flow of Gibson),

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14
Q

Rotary Retinal Flow

A

Produced by non-linear changes in the path with eye and head movements

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15
Q

Snyder and Bischof (2010)

A

2 systems in which we use to make judgements of heading when there is rotary flow disrupting the linear flow:

  • Using motion
  • Retinal Displacement
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16
Q

Retinal Displacement

A

the objects that are nearer to the direction of heading show less retinal
displacement, whilst those nearer the observer show stronger retinal displacement and are
more informative.

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17
Q

Why not just retinal displacement system as a guide for heading?, but also uses motion

A

It is not useful for curved pathways (complex motion direction)
-The first
system uses motion information quickly and automatically
-The second system uses displacement information more slowly

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18
Q

Evidence for 2 part system of heading

A

MST are not
only responsive to expansion, but also to rotation, and even more to a combination of the
two…. So probably this area can compensate for distorted flow fields and decode
information from retinal displacement and factor it in to adjust the visual flow perception.

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19
Q

Curved pathway- Point of Heading

2 Potential strategies

A

Future Path strategy

Tangent-point strategy

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20
Q

Future path strategy

A

The observer identifies a number of point along the future path

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21
Q

Tangent-point strategy

A

the point on the inside edge of the road at which its

direction appears to reverse

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22
Q

Lappi et al (2013)

A

drivers tend to switch from fixating the tangent point to fixating the future path ahead as they negotiate curves. Probably the tangent point provides
relatively precise information. As a result, drivers may use it when uncertainty about the
precise nature of the curve or bend is maximal (i.e., when approaching and entering it).
Thereafter, drivers may revert to focusing on the future path.

23
Q

Visually guided action- TIME TO CONTACT

A

Information that allows us to predict the moment in which there will be contact between us and some objects

24
Q

David Lee (1976) Professor of perception

A

Developed the General Tau Theory

25
General Tau Theory
Provided we are approaching an object at constant velocity, we can use Tau to predict TIME TO CONTACT. Tau= the size of object s retinal image/ rate of expansion
26
Tau
Tau= the size of object s retinal image/ rate of expansion
27
The faster the rate of expansion...
less time there is to contact
28
Limitations of Tau Theory
May provide simple and elegant framework to explain observers’ time-to-contact judgments BUT... -Speed must be constant -Tau provides information about time to contact with the eyes -Tau can only be applied to spherical symmetrical objects
29
Cues that observers use to predict time-to-contact
- Object familiarity -Hosking & Crassini (2010) - Binocular Disparity- steroscopic vision- perceprion of depth - Relative size- De Lucia (2013) - Emotional value of approaching object- Brendel et al. (2012)
30
Summation point about factors influencing Time to contact
Lack of a comprehensive theory that integrates/combines all of the factors influencing time to contact judgements
31
``` Scott Glover (2004) Control model ```
2 systems that enable humans to perform an action, which partially overlap: Planning system and control system
32
Planning system- Control model
Intuitively starts before control system- relatively slow Involves processes prior to movement: -T arget identified (e.g. coffee mug) -A ffordances analysed -M ovement - how this should be carried out -T imings worked out using metrical properties
33
Planning system- control model | Influenced by...
bottom up factors- visual info, affordances, visual context | top down factors- individuals goals, cognitive load
34
Brain areas involved in Planning system
Inferior parietal lobule- processing sensory info, visual representation of object and visual context Prefrontal cortex, motor cortex, basal ganglia- Planning and selection of the correct motor tools
35
Control system- Control model
Starts during execution of movement- faster circuit as not susceptible to conscious influence -Ensures movement is accurate
36
3 components of control system
EFFERENCE COPY=copy of the efferent signal sent to muscles from primary motor cortex- used by the brain to compare actual with desired movement. PROPRIOCEPTION=sensation relating to position of ones body VISUAL PERCEPTION=target object’s spatial characteristics
37
Brain areas involved in Control system
Superior parietal lobe- visual representation formed | Cerebellum and basal ganglia- control of motor processes
38
Glover (2012)
fMRI study defining planning and control systems contrast of brain activation across tasks Results confirm the existence of separate neural systems for the planning and control of reaching and grasping
39
Glover (2005)
the control process was disrupted when TMS was applied to the superior parietal lobe- confirming what model proposed
40
Streiemer et al (2011)
TMS applied to inferior and superior parietal lobes - planning process was more greatly disrupted when applied to the inferior parietal lobe- in line with the control model
41
Evidence for control model from Lesion patients
Ideomotor apraxia- inferior parietal lobe damage- poor at initiating movements in direction of target Optic ataxia- superior and posterior parietal lobe damage- difficulties making accurate movements to perform action
42
Perception of human motion
Humans are very tuned to interpreting other people's movements and actions
43
Gunnar johansson (1998)
Studied perception of the human body in motion
44
Point Light Sequencing
Johansson (1973)- used point lights on human model and found that a figure can be perceived even when it is masked by irrelevant noise dots. Images contained just the few light dots but ppts were still able to identify a figure
45
Mather & Murdoch (1994)
Gender discrimination as a function of view angle. | Participants were very accurate at identify gender-specific differences.
46
Biological motion as innate?
May prove as ontogenic and phlogenic foundation for humans higher order social cognition
47
Simion et al (2008)
Showed pointlight display of chickens to newborns (0 – 3 days) who had no previous experience of them, as well as non-biological motion. Preferred to look at a display showing biological motion
48
experience and human motion perception
- Humans can become increasingly sensitive to human motion due to increased exposure - Also exposure helps develop a better dedicated internal cortical representation of the spatial organisation of the body parts
49
Pinto (2006)
3 month olds = equally sensitive to point-light humans, cats and spiders By 5 months= more sensitive to displays of human motion
50
Influence of own repertoire of actions on human motion perception
Cohen (2002)- point light displays used of humans dogs and seals - performance best with human motion - tested on dog and seal trainers and human motion still better - must be that we recognise motion most similar to that of our own, not just having experience with a type (e.g. seal motion)
51
Specific brain region for human motion?
Superior Temporal Sulcus seems to be of particular importance
52
Thompson et al (2005) –
fMRI- STS strongly responds to moving bodies even through | occlusion, but not to disconnected moving parts.
53
Gilaie-Dotan et al. (2013a)
Grey matter volume in the superior temporal sulcus on motion detection correlated positively with the detection of biological motion but not non-biological motion.