Summary of Social Neuroscience for the first MC exam of chapter 1-4. I summarised the YouTube videos of Jamie Ward and added information from the textbook (in blue text)! Good luck :)!
Summary Social Neuroscience – YouTube videos + book (= blue text)
Chapter 5 – Reading faces and bodies
Visual perception or social perception?
- We cannot observe peoples thoughts and feelings but we can observe their faces and bodies
(and hear their voices too)
- Rooted in evolutionary past
- Need to know whether someone is likely to cooperate or cheat & whether someone is happy
or sad & whether someone is angry and likely to use force
- As such, there is a strong incentive to extract socially relevant info from faces and bodies
- E.g. inferring emotion from expressions
- Inferring intentions from gaze
- Clues as to what’s driving their cognition
- Inferring deception from body language (e.g. in skilled basketball players they
can see through this deception)
- Many believe that we can read character traits, such as trustworthiness and
aggression from faces even when they have neutral facial expressions
- Basic mechanism = visual perception
- To recognize a particular individual (that is my wife)
- Function in real world = social perception
- Extract other types of socially relevant information such as whether the person is
happy, attractive, old, where they are looking, etc.
Going beyond what is given
- Todorov et al. (2005)
- Pairs of faces from US congressional election (winner & runner-up)
- Only unfamiliar faces used
- Discard pairs that are familiar to participants
- Participants asked to rate how competent a person looks
- People agree on a subjective value of competence
- Positive correlation between how competent they are + how well they
won/the margin of victory
- People infer traits from faces (and it influences voting behaviour!)
A cognitive model of face processing Zie figuur 5.2, blz 143 in boek
- Bruce & Young (1986)
1. Earliest level of processing involves structural encoding of the face by detecting shading
and curvature of surfaces and detection of edges
- Take early visual image of face and try and extract a structural description of how
features are related to each other
2. A distinction made between the processing of familiar and unfamiliar faces
- Unfamiliar and familiar
- Recognizing familiar faces is assumed to involve matching the visual
description of the face with stored memory representation of a face
- Create description of a face (mentally rotate a ¾ face to front)
, - Matching a face seen from one particular viewpoint and one particular lighting
condition to a memory representation that stores the three-dimensional structure of the
face
- Enabling it to be recognized from any view
- Map to face recognition units
= A hypothetical entity in models of face processing that responds to the face
of a particular individual
- There is a class of neurons that respond to faces but not objects and they
respond to certain faces more than other faces
- Likely to be coded in terms of the activity of a set of neurons rather than
having a single neuron responding to each known face
- Recognising a familiar person and extracting other kinds of info (e.g. gaze, lip-reading
(visual information amplifies auditory signal), expression) processed differently
3. The semantic level of description (which relates to conceptual knowledge of people,
rather than face per se) is termed the person identity node
- Person identity node = a hypothetical entity in models of face processing that
links together semantic and perceptual information about a particular
individual
4. Other information may become available, such as their occupation or name
- Directed visual processing: separate route to deal with unfamiliar faces
- In order to match them across different views/lighting conditions
- Evidence from prosopagnosia
= Impairments of face processing that do not reflect difficulties in early visual
analysis/inability to recognize previously familiar faces
- People lose ability to recognise familiar faces but can perform process of model
- Recognize them by their voices or other non-facial information
- Recognize other socially salient information from faces, including sex, age
and emotional expressions
- Can use lip-reading cues to aid in speech perception
- Can see but all faces look the same
- Can see a face as a face, but not the individuation
- Can also be born with this = congenital prosopagnosia
- Is present throughout the lifespan with no known external cause
A neural model
- Ventral visual stream: concerned with identifying objects, largely irrespective of where they
are
- Face perception primarily depends on this stream
- Dorsal visual stream: concerned with locating objects, largely irrespective of what they are
- Haxby et al. (2000)
- Core regions involved in face perception to lie in fusiform gyrus in humans and the STS
- Division into ‘core system’ (face specialised) and ‘extended system’ (face-related, but more
general functions)
- Core system: neural resources that are relatively specialised for faces
- Extended system: face processing along with other things
- Not face specific
- Invariant aspects: things that don’t change
- Dynamic aspects: gaze for example
,- Occipital face area (OFA): physical aspects of face
- Fusiform face area (FFA): invariant aspects
- Recognising who a person is
- Superior temporal sulcus (STS): more changeable aspects (gaze)
- Evidence from fMRI
OFA
= Early (pre-categorical) perceptual region that processes the physical properties of faces
- Located in the inferior occipital gyrus
- Early stage in perceptual analysis of faces that sends inputs to fusiform and superior
temporal regions
- Larger BOLD response for faces than for objects/other categories
- OFA responds to both upright and inverted faces, whereas the FFA responds more to upright
faces
- Sensitive to any physical change in face stimulus
- Insensitive to categorical perception; e.g. when morphing of faces from Marilyn Monroe to
Margaret Thatcher
- Categorical perception = the tendency to perceive ambiguous or hybrid stimuli as
either one thing or the other (rather than both as simultaneously or as a blend)
- OFA related to degree of any physical difference between images
- FFA related to who the participants perceives it to be
- When identity was perceived to change
- You habituate if you’re seeing the same thing
- BOLD signal is reduced when the same stimulus is presented twice
- Categorically the same: 100% & 70% Thatcher
- Change within or between categories pushes the BOLD response up
- FFA just responds when an image is categorically different
- Who is this person?
FFA
= Primarily concerned with discriminating between facial identities and may act as a store of
known faces
- Responds to (upright) faces more than other kinds of visual stimuli
- More tuned to environment
- Used to see faces one way round
- Particularly important for recognizing known faces
- FFA is found bilaterally with a generally more robust BOLD response on the right
- Degree of left/right asymmetry differs between individuals and is related to
individual differences in visual field asymmetry for identifying faces
- fMRI adaptation shows it responds when same face is repeated even if different images of
the face are used/even if physical aspects of the images change
- Lesion location of acquired prosopagnosia varies, but the evidence is broadly consistent with
damage in or around the FFA
- Rival claim = within-category expertise
- Faces require discrimination within a category (between one face and another)
- Whereas most other object recognition requires a superordinate level of
discrimination (between comb and cup)
, - We’ve become ‘visual experts’ at making within-category distinctions through
prolonged experience
- Face perception and visual within-category expertise are not necessarily the same`
thing
- Is it face specific?
- Train participants to recognise non-facial stimuli and see which family it is
- Move from part-based to holistic processing
- Activate the FFA
- “They are like faces”
- Maybe evolved for faces and also cars and dogs?
STS
- According to Haxby et al. (2000) responds to changeable aspects of face (gaze, expression)
- FFA responds to stable aspects of a face (person’s identity)
- Not who it is, but more social aspects of the face
- Particularly important for extracting social cues that are likely to be fleeting
- Judging gaze direction (whether the face is looking in same direction as the last face)
activates STS not FFA, but judging face identity (whether the face is the same as the last one)
activates FFA not STS
- Same set of faces but different judgements
- Where is person looking (STS > FFA) & who is the person (FFA > STS)
- Responds to bodies as well as faces
- Linking the ventral visual stream with the dorsal stream
- Enables dynamic visual percpets of faces and bodies in the STS to be processed
motorically
A mirroring of the other’s action in one’s own motor system
- Integrates different sensory inputs (e.g. evidence from primate single cell recordings)
seen speech (facial lip-reading) and heard speech
- See somebody moving their lips (monkey signal) + hear various sounds at the same
time (that signal or something else)
- Vision + corresponding sounds helps neurons boost firing rate
- Vision alone + with ‘wrong’ sound not the same level of activity
- Respond to sounds as well as vision
Recognising expressions
- Both models make distinction between facial identity and expression, but neither model has
a complete account of data
- Haxby et al: expressions important simply because they are dynamic
- Bruce & Young: specialised module from dealing with expressions
- Separate route for analysing facial expressions
- Although prosopagnosic patients have been reported who are better at recognizing facial
expressions than facial identity, Calder and Young (2005) argue that the dissociation is not
absolute
- Both facial expression and facial identity tend to be impaired in prosopagnosia
relative to controls, even though recognition of facial expressions is less impaired
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