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!