Expressing fear enhances sensory acquisition

1. Expressing fear enhances sensory acquisition Susskind et al., Nature Neuroscience, 11, 843-850 (2008) Presented by: Kara Hawkins

2. 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

3. Paul Ekman • Social communication • Cultural invariance in the recognition of facial expressions Ekman, P. & Friesen, W. J. Pers. Soc. Psychol., 17 124-129 (1971)

4. Carroll E. Izard • Innate & universal facial expressions • Developmental & cross-cultural research Izard, C.E. Psychol. Bull., 115, 288-299 (1994)

5. 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)

6. Adolphs,R. Behav. Cogn. Neurosci. Rev. 1, 21-62 (2002)

7. 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)

8. Gallese & Adolphs have begun to consider some of the mechanisms involved in the production of facial expressions, however they have not addressed the questionof why particular facial muscle actions are associated with specific emotional states 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)

9. Why do we look the way we do in certain situations? Whalen P.J. & Kleck R.E. Nat. Neurosci., 11, 739-740 (2008)

10. 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)

11. 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

12. 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

13. Face Stimuli • 8 face exemplars for each of the 6 basic emotions were used to train the appearance model

14. 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)

15. Prototypical fear Antiprototypical fear • 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) Prototypical disgust Antiprototypical disgust

16. Subjective ratings • Fear antiprototype was rated maximally as disgust • Disgust antiprototype was rated maximally as fear

17. In 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. Antifear to fear Antidisgust to disgust Vector flow fields • Derived from the surface deformations that occur as the face moves from: Spreading longitudinal action Contracting longitudinal action

18. 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

19. 135° 45° Fear Neutral baseline • 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. 315° 225° Vertical eye-size relative to neutral Disgust Size of upper-visual field relative to neutral Visual-field estimation experiment

20. Both average & peak velocities increased from disgust to fear Reliably faster than neutral expressions According to these results, expressions of fear enhance and expressions of disgust decrease the velocity of horizontal saccadic eye movements during target localization. Pronounced slowing relative to neutral expressions Eye movement experiment

21. Increased mean air-flow velocity over time Increased 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. Decreased mean air-flow velocity over time Decreased inspiration volume Nasal inspiration experiment

22. Fearful axial slice Disgusted axial slice Disgust Neutral Fear Closed Dilated MRI of nasal passage: case study

23. 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 MRI of nasal passage: case study Volume of air cavity in ventral portion of nasal passages Average overall air cavity volume

24. 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

25. 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

26. 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)

27. 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

28. Thank You!