expressing fear enhances sensory acquisition presented by: kara hawkins susskind et al., nature...
TRANSCRIPT
Expressing fear enhances sensory
acquisition
Presented by: Kara Hawkins
Susskind et al., Nature Neuroscience, 11, 843-850 (2008)
Overview of Susskind’s Story Everybody talks about the behavioural & neural
bases of emotional expression recognition Ekman, Izard, Adolphs, Gallese
But what about the production of emotional expression? Why do our facial expressions look the way they do? Darwin (origin of facial expressions)
Principle of form Principle of function Provide evidence for Darwin’s view that facial
expressions look the way that they do because their form serves a function that is beneficial to the survival of the organism
Paul Ekman Social communication Cultural invariance in the
recognition of facial expressions
Ekman, P. & Friesen, W. J. Pers. Soc. Psychol., 17 124-129 (1971)
Carroll E. Izard Innate & universal facial
expressions Developmental & cross-
cultural research
Izard, C.E. Psychol. Bull., 115, 288-299 (1994)
Ralph Adolphs Demonstrated the
existence of dedicated neural substrates for the recognition of emotion from facial expressions
Adolphs, R. Behav. Cogn. Neurosci. Rev. 1, 21-62 (2002)
Adolphs,R. Behav. Cogn. Neurosci. Rev. 1, 21-62 (2002)
Ralph Adolphs Demonstrated the
existence of dedicated neural substrates for the recognition of emotion from facial expressions
Suggested a common circuitry for perceiving & generating facial expressions
Adolphs, R. Behav. Cogn. Neurosci. Rev. 1, 21-62 (2002)
Vittorio Gallese Suggested that emotion
recognition is “accomplished through mirroring motor actions to infer the mental states of others”
Shared emotional experiences result from simulated action and thus emotional resonance (empathy) in the observer
Gallese, V. Philos. Trans. R. Soc. B. Biol. Sci., 362, 659-669 (2007)
Gallese & Adolphs have begun to consider some of the mechanisms involved in the production of facial expressions, however they have not addressed the question of why particular facial muscle actions are associated with specific emotional states
Why do we look the way we do in certain situations?
Whalen P.J. & Kleck R.E. Nat. Neurosci., 11, 739-740 (2008)
Charles Darwin This sort of question was
first seriously asked by Darwin (The Expression of the Emotions in Man and Animals, 1872/1998)
Facial expressions originated for the purpose of modifying preparedness for perception & action (i.e. augmenting or diminishing exposure to environmental stimuli)
Joshua Susskind (et al.) Sought evidence for two
of Darwin’s principles 1) Principle of form:
Emotions with opposite functions are opposites in facial action
2) Principle of function: Facial expressions originate in action patterns serving adaptive information processing
1) Principle of form
Used a computer-graphics based model of facial appearance to examine the action tendencies underlying and opposing fear expressions
Specifically interested in the physical appearance of the facial expression of fear
Face Stimuli
8 face exemplars for each of the 6 basic emotions were used to train the appearance model
Computer model Represents each face as a vector in a
multidimensional space, coding variations is shape & surface reflectance
Expression prototypes for fear & disgust were created by averaging the vector representations of all exemplars from these two categories
Faces were then synthesized at successive intervals along “expression trajectories” (from the prototypical expression to the antiprototypical expression, i.e. an expression containing opposing shape & surface reflectance features)
Prototypical fear
Prototypical disgust
Antiprototypical fear
Antiprototypical disgust
Fear antiprototypes were most similar in structure to disgust (r = 0.69)
Disgust antiprototypes were most similar to fear (r = 0.69) and surprise (r = 0.70)
Subjective ratings Fear antiprototype was rated maximally as
disgust Disgust antiprototype was rated maximally
as fear
Vector flow fields Derived from the surface deformations that
occur as the face moves from:
Spreading longitudinal action Contracting longitudinal action
Antifear to fear Antidisgust to disgustIn sum, according to this computer animation model, the physical appearance (form) of fear, an emotion associated with sensory vigilance, opposes the physical appearance of disgust, an emotion associated with sensory rejection.
2) Principle of function
Does this opposition in the physical appearance of facial expressions of fear & disgust reflect evolutionarily adaptive action tendencies?
If so, these expressions should retain some residue of this function
Several studies were conducted to measure differences in sensory regulation when the face is posed to simulate the expression of fear and when it is posed to simulate the expression of disgust
45°135°
225° 315°
Visual-field estimation experiment
Neutralbaseline
Disgust
Fear
Size of upper-visual field relative to neutral
Vertical eye-size relative to neutral
• Also demonstrated that participants could detect objects at farther eccentricities in the upper visual field during the fear condition• Together, these results demonstrate that fear expressions enhance and disgust expression reduce the overall size of the visual field & stimulus detection in the upper visual field.
Eye movement experiment
Reliably faster than neutral expressions
Pronounced slowingrelative to neutral expressions
Both average & peak velocitiesincreased from disgust to fear
According to these results, expressions of fear enhance and expressions of disgust decrease the velocity of horizontal saccadic eye movements during target localization.
Nasal inspiration experimentIncreased mean air-flow velocity over time
Decreased mean air-flow velocity over time
Increased inspiration volume
Decreased inspiration volume
Since changes in air intake can be explained by a variety of factors & may not necessarily reflect structural changes in sensory capacity, the authors decided to expand upon these findings by taking a look at changes in the internal anatomy of the nasal passages.
MRI of nasal passage: case studyFearful axial slice Disgusted axial slice
Disgust Neutral Fear
DilatedClosed
MRI of nasal passage: case study
Volume of air cavity in ventral portion of nasal passages
Average overall air cavity volume
These results indicate that fearful facial expressions facilitate nasal passage dilation, while disgusted facial expressions result in sealing off these nasal passages, which normally remain open. These changes in nasal anatomy may be responsible for the changes in nasal inspiration revealed in the previous experiment
Summary of support for Darwin’s principles Fear & disgust were shown to be near
opposites in form, supported by opposing action patterns
A parallel opposition in function between fear & disgust was reveled by evidence for enhanced visual-field size, saccadic velocity, & nasal inspiration capacity in fear & the direct inverse in disgust
What do these results mean? The authors suggest that human facial
expressions likely originated in an innate functional capacity to alter sensory processing & sensory exposure (i.e. egocentric function)
But they are maintained & have been further shaped based on social pressures (i.e. empathetic function)
In other words, the functional & signal (communication) value of facial expressions have probably co-evolved such that the functional importance for the sender is coupled with communicative importance for the receiver
Non-human primates Idea supported by
observing facial expressions in non-human primates
These expressions serve as innate protective reflexes, but like human expressions they have become important for social communication
Andrew, R.J. Science, 142, 1034-1041 (1963); Whalen P.J. & Kleck R.E. Nat. Neurosci., 11, 739-740 (2008)
Take home message
Facial expressions may have originally evolved based on their adaptive role in preparing the organism for perception & action
It is likely, however, that the form & function of facial expressions in the present day reflect selection pressures from both biological & social sources
Thank You!