Expressing fear enhances sensory acquisition Susskind et al., Nature Neuroscience, 11, 843-850 (2008) Presented by: Kara Hawkins 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 & crosscultural 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 Gallese & Adolphs have begunmirroring to consider some of theto motor actions mechanisms involved in the production of facial infer the mental states of expressions, however they have not addressed the others” question of why particular facial muscleemotional actions are Shared associated with specific emotional states result from experiences simulated action and thus emotional resonance (empathy) in the observer Gallese, V. Philos. Trans. R. Soc. B. Biol. Sci., 362, 659-669 (2007) 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: In sum, according animation Antifear to fear to this computer Antidisgust tomodel, disgust the physical appearance (form) of fear, an emotion associated with sensory vigilance, opposes the physical appearance of disgust, an emotion associated with sensory rejection. Spreading longitudinal action Contracting longitudinal action 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 Visual-field estimation experiment Fear 135° 45° • Also demonstrated that participants could detect Neutral baseline objects at farther eccentricities in the upper visual field during the fear condition 315°demonstrate Vertical eye-sizethat fear • Together, 225° these results expressions enhance andrelative disgust expression reduce to neutral the overall size of the visual field & stimulusDisgust detection in the upper visual field. Size of upper-visual field relative to neutral Eye movement experiment Reliably faster than neutral expressions Both average & peak velocities increased 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. Pronounced slowing relative to neutral expressions Nasal inspiration experiment 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 MRI of nasal passage: case study Fearful axial slice Disgust Closed Disgusted axial slice Neutral Fear Dilated MRI of nasal passage: case study 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 Volume of air cavity in ventral portion of nasal passages Average overall air cavity volume 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 nonhuman 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!