Week 10 - Face and Voices Flashcards
1
Q
What’s in a face?
A
- Identity
- Emotion
- Speech
- Gaze direction
- Physical attributes
- Social attributes
2
Q
What are the three things that makes faces special?
A
Configural Processing:
- Infant orienting - from birth, humans’ orient attention to faces
- Face inversion effect - Yin (1969) – faces are processed differently to other visual objects (e.g. houses, planes, etc.):
- Thatcher illusion - a special case of the face inversion effect where it is more difficult to detect distortion of facial features when faces are inverted
Holistic processing:
- Composite face effect - humans perceive faces as a whole rather than a collection of different features
3
Q
What are the two models of face perception?
A
- Bruce & Young (1986) - structural encoding:
- 4 separate pathways:
- Emotion
- Speech
- Identity - familiar face perception vs. unfamiliar face perception (direct visual pathway).
- Haxby (2000):
- Core system = face-specific:
- Inferior occipital gyri - occipital face area (OFA)
- Lateral fusiform gyrus - fusiform gyrus (FFA)
- Superior temporal sulcus (STS)
- Extended system = domain-general
- Regions involved in more general cognitive processing
4
Q
What evidence is there for these models?
A
Two main sources of evidence:
- Face processing can be selectively disrupted
- There is a distinct neural substrate for processing faces
5
Q
What is prosopagnosia?
A
- Prosopagnosia - selective deficit in recognising familiar faces in the absence of any other visual or cognitive impairments
6
Q
What is the occipital face area (OFA)?
A
Occipital Face Area:
- Responds more to faces > other objects
- No face inversion effect
- Sensitive to changes in face parts
7
Q
What is the fusiform face area (FFA) and describe the study associated with it
A
Fusiform Face Area (FFA) - Kanwisher et al. (1999):
- Participants - 15 people
- Stimuli:
- Human faces - stimulus of interest
- Objects - baseline comparison
- Scrambled faces - low-level visual features
- Houses - within-category discrimination
- Task - passive viewing
- Results:
- More activation for Faces > houses, scrambled faces, and houses
- More activation for Upright > inverted faces
- Sensitive to face identity
8
Q
What is the superior temporal sulcus (STS)?
A
Superior Temporal Sulcus (STS):
- Gaze direction
- Emotional expressions
- Facial speech
9
Q
What is the EEG response to faces in the brain?
A
EEG response to faces in the brain – Bentin et al. (1996):
- Participants - 12 people/experiment
- Stimuli:
- Human faces - stimulus of interest
- Animal faces - face of other species
- Hands - human body part
- Furniture - other object category
- Task - target detection: count number of stimuli in the target category
- Results:
- N170 - Larger for human faces compared to all other categories. Delayed for inverted compared to upright faces –> faster processing of upright faces
- “N170 may reflect the operation of a neural mechanism tuned to detect (as opposed to identify) human faces, similar to the “structural encoder” suggested by Bruce and Young (1986).”
10
Q
However, are faces really that special?
A
Two alternative explanations:
- Within-category discrimination
- Visual expertise
Prosopagnosia:
- Bornstein et al. (1969) - farmer with acquired prosopagnosia could no longer recognise his cattle
- But McNeil & Warrington (1993) - sheep owner with acquired prosopagnosia could still distinguish between his sheep
What might account for these differences?
- Wide-spread brain lesions (not just to the FFA)
- Compensatory strategies
Gauthier et al. (2000) – looked at expertise for cards and birds recruits brain areas involved in face recognition:
- Participants:
- 8 bird experts
- 11 car experts
- Stimuli:
- Faces, birds, cars, and objects
- Task:
- “1-back” – detect repetitions of identity or location of the preceding stimulus
- Results:
- Both groups - higher FFA activation for faces > objects
- Bird experts - higher FFA activation for birds > objects
- Car experts - higher FFA activation for cars > objects
Gauthier et al. (1999) - activation of the middle FFA increases with expertise in recognizing novel objects:
- Participants:
- 12 people (6 experts, 6 non-experts)
- Stimuli:
- Faces
- Greebles
- Task:
- Part 1: Training
- Part 2: Test
- “Same or different?”
- Results:
- Greeble novices:
- Higher FFA activation for faces > objects
- No difference between Greebles & objects
- Greeble experts:
- Higher FFA activation for faces > objects
- Higher FFA activation for Greebles > objects
Summary:
- Faces are processed holistically and configurally, in a way that differs from other objects
- Models of face perception distinguish between early structural encoding and subsequent recognition of identity (familiar/unfamiliar), emotion, and speech
- Faces are processed ‘specially’ in the brain
- (Familiar) face processing can be selectively disrupted in prosopagnosia
- Faces appear to have a distinct neural substrate (FFA/N170)
- However, it is difficult to match the level of visual expertise that humans have with faces, so other processes could also be at play
11
Q
What is a voice?
A
- “an acoustic signal produced by the anatomical and physiological vocal tract system…that is acoustically registered and auditorily perceived…as a distinctive vocal auditory object”
- Dichotomies of the voice:
- Perception versus production
- Speech versus non-verbal vocalisations
12
Q
What’s in a voice?
A
- Identity
- Emotion
- Speech
- Social attributes
- Physical attributes
- BUT no gaze direction, instead location
13
Q
How does our brain respond to voices?
A
Voice recognition in infants:
- Kisilevsky et al. (2009) – In utero - changes in heart rate in response to parent voices
- Grossmann, Oberecker, Koch & Friederici (2010) - 4-7 months: cortical brain regions respond more to vocal > non-vocal sounds
A voice inversion effect?
- Bédard, C., & Belin, P. (2004):
- Not inverted > inverted
- BUT…same for voices and instruments
14
Q
What is phonagonisa and outline the case of KH
A
Are voices treated ‘specially’ by the brain? Two main sources of evidence:
- Voice processing can be selectively disrupted
- There is a distinct neural substrate for processing voices
Phonagnosia - selective deficit in processing familiar voices:
- Van Lancker & Canter (1982) - patients with damage encompassing the temporal lobe:
- Left hemisphere associated with speech difficulties (aphasia)
- Right hemisphere associated with recognition difficulties (prosopagnosia and phonagnosia)
- But…many patients also had other impairments
- Case KH (Garrido et al., 2009):
- 60-year -old woman who reported severe difficulty recognising people over the telephone but no neurological abnormalities
- Only answered “booked calls” so that she knew who it would be on the other end of the line
- Used a different form of her name at work so that she would know when it was a work colleague who called
15
Q
What does fMRI show about the processing of voices?
A
Belin et al. (2000):
- Participants - 8 people
- Stimuli: Voices, Non-human sounds, Human non-vocal sounds, and Bells
- Task - Passive listening
- Temporal voice areas (TVAs) activated for:
- Vocal > non-vocal sounds
- Voices > scrambled voices
- Both speech & non-speech sounds
