Abstract
This review focuses on facial asymmetries during emotional expression. Facial asymmetry is defined as the expression intensity or muscular involvement on one side of the face (“hemiface”) relative to the other side and has been used as a behavioral index of hemispheric specialization for facial emotional expression. This paper presents a history of the neuropsychological study of facial asymmetry, originating with Darwin. Both quantitative and qualitative aspects of asymmetry are addressed. Next, neuroanatomical bases for facial expression are elucidated, separately for posed/voluntary and spontaneous/involuntary elicitation conditions. This is followed by a comprehensive review of 49 experiments of facial asymmetry in the adult literature, oriented around emotional valence (pleasantness/unpleasantness), elicitation condition, facial part, social display rules, and demographic factors. Results of this review indicate that the left hemiface is more involved than the right hemiface in the expression of facial emotion. From a neuropsychological perspective, these findings implicate the right cerebral hemisphere as dominant for the facial expression of emotion. In spite of the compelling evidence for right-hemispheric specialization, some data point to the possibility of differential hemispheric involvement as a function of emotional valence.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Albert, M. S., and Kaplan, E. (1980). Organic implications of neuropsychological deficits in the elderly. In Poon, L. W., Fozard, J. L., Cermak, L. S., Ahrenberg, D., and Thompson, L. W. (eds.),New Directions in Memory and Aging: Proceedings of the George A. Talland Memorial Conference, Lawrence Erlbaum, Hillsdale, NJ, pp. 403–432.
Alford, R. (1983). Sex differences in lateral facial facility: The effects of habitual emotional concealment.Neuropsychologia 21: 567–570.
Alford, R., and Alford, K. (1981). Sex differences in asymmetry in the facial expression of emotion.Neuropsychologia 19: 605–608.
Allport, G. W. (1961).Pattern and Growth in Personality, Holt, Rinehart, and Winston, New York.
Baribeau, J., Guérette, R., and Braun, C. (1987).Hemifacial production of posed emotional expression in normal men and women. Paper presented at the meeting of the International Neuropsychological Society, Washington, DC.
Blonder, L., Burns, A., Bowers, D., Moore, R., and Heilman, K. M. (1993). Right-hemisphere facial expressivity during natural conversation.Brain and Cognition 21: 44–56.
Borod, J. (1992). Interhemispheric and intrahemispheric control of emotion: A focus on unilateral brain damage.Journal of Consulting and Clinical Psychology 60: 339–348.
Borod, J. (1993). Cerebral mechanisms underlying facial, prosodic, and lexical emotional expression: A review of neuropsychological studies and methodological issues.Neuropsychology 7: 445–463.
Borod, J., and Caron, H. S. (1976, March).Facial expression and cognitive control. Invited paper presented at the Cortical Functions Laboratory, Johns Hopkins Medical Center, Baltimore, MD.
Borod, J., and Caron, H. S. (1979, February).Facial asymmetry during emotional expression. Paper presented at the International Neuropsychological Society, New York City, NY.
Borod, J., and Caron, H. (1980). Facedness and emotion related to lateral dominance, sex, and expression type.Neuropsychologia 18: 237–242.
Borod, J., and Goodglass, H. (1980). Lateralization of linguistic and melodic processing with age.Neuropsychologia 18: 79–83.
Borod, J., and Koff, E. (1983). Hemiface mobility and facial expression asymmetry.Cortex 19: 335–361.
Borod, J., and Koff, E. (1984). Asymmetries in affective facial expression: Anatomy and behavior. In Fox, N., and Davidson, R. (eds.),The Psychobiology of Affective Development, Lawrence Erlbaum Associates, Hillsdale, NJ, pp. 293–323.
Borod, J., and Koff, E. (1990). Lateralization for facial emotional behavior: A methodological perspective.International Journal of Psychology 25: 157–177.
Borod, J., and Koff, E. (1991). Facial asymmetry during posed and spontaneous expression in stroke patients with unilateral lesions.Pharmacopsychoecologia 4: 15–21.
Borod, J., and Van Gelder, R. S. (1990). Facial asymmetry: Expression and paralysis [Special Issue].International Journal of Psychology 25: 2.
Borod, J., Caron, H., and Koff, E. (1981). Asymmetry of facial expression related to handedness, footedness, and eyedness: A quantitative study.Cortex 17: 381–390.
Borod, J., Kent, J., Koff, E., Martin, C., and Alpert, M. (1988). Facial asymmetry while posing positive and negative emotions: Support for the right hemisphere hypothesis.Neuropsychologia 26: 759–764.
Borod, J., Koff, E., and Buck, R. (1986). The neuropsychology of facial expression in normal and brain-damaged subjects. In Blanck, P., Buck, R., and Rosenthal, R. (eds.),Nonverbal Communication in the Clinical Context, Pennsylvania State University Press, University Park, PA, pp. 196–222.
Borod, J., Koff, E., and Caron, H. (1983). Right hemispheric specialization for the expression and appreciation of emotion: A focus on the face. In Perecman, E. (ed.),Cognitive Functions in the Right Hemisphere, Academic Press, New York, pp. 83–110.
Borod, J., Koff, E., Lorch, M., and Nicholas, M. (1986). The expression and perception of facial emotion in brain-damaged patients.Neuropsychologia 24: 169–180.
Borod, J., Koff, E., and White, B. (1983). Facial asymmetry in spontaneous and posed expressions of emotion.Brain and Cognition, 2: 165–175.
Borod, J., St. Clair, J., Koff, E., and Alpert, M. (1990). Perceiver and poser asymmetries in processing facial emotion.Brain and Cognition 13: 167–177.
Brockmeier, B., and Ulrich, G. (1993). Asymmetries of expressive facial movements during experimentally induced positive versus negative mood states: A video-analytic study.Cognition and Emotion 7: 393–405.
Brown, J., and Jaffe, J. (1975). Hypothesis on cerebral dominance.Neuropsychologia 3: 107–110.
Buck, R. (1978). The slide-viewing techniques for measuring non-verbal sending accuracy: A guide for replication.Catalog of Selected Documents in Psychology 8: 63.
Buck, R. (1984).The Communication of Emotion, Guilford, New York.
Buck, R., and Duffy, R. J. (1980). Nonverbal communication of affect in brain-damaged subjects.Cortex 16: 351–362.
Cacioppo, J. T., and Petty, R. E. (1981). Lateral asymmetry in the expression of cognition and emotion.Journal of Experimental Psychology: Human Perception and Performance 7: 333–341.
Campbell, R. (1978). Asymmetries in interpreting and expressing a posed facial expression.Cortex 14: 327–342.
Campbell, R. (1979). Left-handers’ smiles: Asymmetries in the projection of a posed expression.Cortex 14: 571–579.
Campbell, R. (1982). Asymmetries in moving faces.British Journal of Psychology 73: 95–103.
Campbell, R. (1986). Asymmetries of facial action: Some facts and fancy of normal face movement. In Bruyer, R. (ed.),The Neuropsychology of Face Perception and Facial Expression, Erlbaum, Hillsdale, NJ, pp. 247–267.
Carlson, D. F., and Harris, L. J. (1986, February).Perception of happiness and sadness in free-viewing of chimeric faces. Paper presented at the meeting of the International Neuropsychological Society, Denver, CO.
Chaurasia, B. D., and Goswami, H. K. (1975). Functional asymmetry in the face.Acta Anatomica 91: 154–160.
Chusid, J. G., and McDonald, J. F. (1976).Correlative Neuroanatomy and Functional Neurology (17th ed.), Lange Medical Publications, Los Altos, CA.
Crosby, E. G., and De Jonge, B. R. (1963). Experimental and clinical studies of the central connections and central relations of the facial nerve.Annals of Otology, Rhinology, and Laryngology 72: 735–755.
Damasio, A. R., and Maurer, R. G. (1978). A neurological model for childhood autism.Archives of Neurology 35: 777–786.
Darwin, C. (1890).The Expression of the Emotions in Man and Animals, D. Appleton and Co., New York.
Davidson, R. (1984). Affect, cognition, and hemispheric specialization. In Izard, C. E., Kagan, J., and Zajonc, R. (eds.),Emotions, Cognition, and Behavior, Cambridge Press, Cambridge, England, pp. 320–365.
Davidson, R. (1993). Parsing affective space: Perspectives from neuropsychology and psychophysiology.Neuropsychology 7: 464–475.
Davidson, R., Ekman, P., Saron, C. D., Senulis, J. A., and Friesen, W. V. (1990). Approach-withdrawal and cerebral asymmetry: Emotion expression and brain physiology I.Journal of Personality and Social Psychology 58: 330–341.
DeJong, R. N. (1979).The Neurologic Examination, Harper and Row, New York.
Diamond, C., and Frew, I. (1979).The Facial Nerve, Oxford University Press, New York.
Dopson, W. G., Beckwith, B. E., Tucker, D. M., and Bullard-Bates, P. C. (1984). Asymmetry of facial expression in spontaneous emotion.Cortex 20: 243–251.
Dyken, P., and Miller, M. D. (1980).Facial Features of Neurologic Syndromes, C. V. Mosby, St. Louis, MO.
Egan, G. J., Kilts, C. D., Gideon, D. A., Hoffman, J. M., and Faber, T. (1996, August).PET analysis of hemispheric involvement in human face perception. Paper presented at the annual meeting of the American Psychological Association, Toronto, Ontario.
Ehrlichman, H. (1987). Hemispheric asymmetry and positive-negative affect. In Ottoson, D. (ed.),Duality and Unity of the Brain, Macmillan, Hampshire, England, pp. 194–206.
Ekman, P. (1980). Asymmetry in facial expression.Science 209: 833–834.
Ekman, P., and Friesen, W. V. (1969). The repertoire of nonverbal behavior: Categories, origins, usage, and coding.Semiotics 1: 49–98.
Ekman, P., and Friesen, W. V. (1978).Facial Action Coding System, Consulting Psychologists Press, Palo Alto, CA.
Ekman, P., Hager, J. C., and Friesen, W. V. (1981). The symmetry of emotional and deliberate facial actions.Psychophysiology 18: 101–105.
Ellis, R., and Oscar-Berman, M. (1989). Alcoholism, aging, and functional cerebral asymmetries.Psychological Bulletin 106: 128–147.
Erwin, R. J., Gur, R. C., Gur, R. E., Skolnick, B., Mawhinney-Hee, M., and Smailis, J. (1992). Facial emotion discrimination: I. Task construction and behavioral findings in normal subjects.Psychiatry Research 42: 231–240.
Etcoff, N. (1986). The neuropsychology of emotional expression. In Goldstein, G., and Tarter, R. E. (eds.),Advances in Clinical Neuropsychology, Plenum Press, New York, pp. 127–175.
Fox, N. A. (1991). If it’s not left, it’s right.American Psychologist, 46: 863–872.
Fridlund, A., Ekman, P., and Oster, H. (1987). Facial expressions of emotion: Review of the literature 1970–1983. In Siegman, A., and Feldstein, S. (eds.),Nonverbal Behavior and Communication, Erlbaum, Hillsdale, NJ, pp. 143–224.
Gainotti, G. (1972). Emotional behavior and hemispheric side of lesion.Cortex 8: 41–55.
Gainotti, G., Caltagirone, C., and Zoccolotti, P. (1993). Left-right and cortical/subcortical dichotomies in the neuropsychological study of human emotions.Cognition and Emotion 7: 71–93.
Gardner, H. (1975).The Shattered Mind: The Person after Brain Damage, A. A. Knopf, New York.
George, M., Ketter, T. A., Gill, D. S., Haxby, J. V., Ungerleider, L. G., Herscovitch, P., and Post, R. M. (1993). Brain regions involved in recognizing facial emotion or identity: An Oxygen-15 PET study.Journal of Neuropsychiatry 5: 385–394.
Geschwind, N. (1979). Specializations of the human brain.Scientific American 241: 180–199.
Goffman, E. (1958).The Presentation of Self in Everyday Life, Doubleday, New York.
Goldberg, E., and Costa, L. (1981). Hemisphere differences in the acquisition and use of descriptive systems.Brain and Language 14: 144–173.
Güntürkün, O. (1991). The Venus of Milo and the dawn of facial asymmetry research.Brain and Cognition 16: 147–150.
Hager, J. C. (1982). Asymmetries in facial expression. In Ekman P. (ed.),Emotion in the Human Face, Cambridge University Press, Cambridge, England, pp. 318–352.
Hager, J. C., and Ekman, P. (1985). The asymmetry of facial actions is inconsistent with models of hemispheric specialization.Psychophysiology 22: 307–318.
Hallervorden, J. (1902). Eine neue methode experimenteller physiognomik. [A new method of experimental physiognomy.]Psychiatrisch-Neurologische Wochenschrift 28: 309–311.
Hallervorden J. (1929). Rechts-und Linkshandig-keit und Gesichtausdruck. [Right-and left-handedness and facial expression.]Zentralbatt fur die gesamte Neurologie und Psychiatrie 53: 560.
Heilman, K. M., Scholes, R., and Watson, R. T. (1975). Auditory affective agnosia: Disturbed comprehension of affective speech.Journal of Neurology, Neurosurgery, and Psychiatry 38: 69–72.
Heller, W., and Levy, J. (1981). Perception and expression of emotion in right-handers and left-handers.Neuropsychologia 19: 263–272.
Izard, C. E. (1983).The Maximally Discriminative Facial Movement Coding System, Instructional Resources Center, University of Delaware, Newark, DE.
Jaeger, J. (1984).The neuropsychology of emotion in major depressive disorder. Unpublished doctoral dissertation, Yeshiva University, New York.
Jaeger, J., Borod, J., and Peselow, E. (1987). Depressed patients have atypical hemispace biases in the perception of emotional chimeric faces.Journal of Abnormal Psychology 96: 321–324.
Kahn, E. A. (1964). Facial expression.Clinical Neurosurgery 12: 9–22.
Karch, G. R., and Grant, C. W. (1978). Asymmetry in perception of the sides of the human face.Perceptual and Motor Skills 47: 727–734.
Kent, J., Borod, J., Koff, E., Welkowitz, J., and Alpert, M. (1988). Posed facial emotional expression in brain-damaged patients.International Journal of Neuroscience 43: 81–87.
Kinsbourne, M. (1982). Hemispheric specialization and the growth of human understanding.American Psychologist 37: 411–420.
Kinsbourne, M., and Bemporad, B. (1984). Lateralization of emotion: A model and the evidence. In Fox, N., and Davidson, R. (eds.),The Psychobiology of Affective Development, Erlbaum Press, Hillsdale, NJ, pp. 259–291.
Koff, E., Borod, J., and White, B. (1981). Asymmetries for hemiface size and mobility.Neuropsychologia 19: 825–830.
Kop, W. J., Merckelbach, H., and Muris, P. (1991). Unilateral contraction of facial muscles and emotion: A failed replication.Cortex 27: 101–104.
Kowner, R. (1995). Laterality in facial expressions and its effect on attributions of emotion and personality: A reconsideration.Neuropsychologia 33: 539–559.
Kuypers, H. G. J. M. (1958). Corticobulbar connections to the pons and lower brainstem in man.Brain 81: 364–390.
Levy, J. (1974). Psychobiological implications of bilateral asymmetry. In Dimond, S. J., and Beaumont, J. G. (eds.),Hemisphere Function in the Human Brain, John Wiley & Sons, New York, pp. 121–183.
Levy, J., Heller, W., Banich, M. T., and Burton, L. A. (1983). Asymmetry of perception in free viewing of chimeric faces.Brain and Cognition 2: 404–419.
Libby, W. L., and Yaklevich, D. (1973). Personality determinents of eye contact and direction of gaze aversion.Journal of Personality and Social Psychology 27: 197–206.
Lindzey, G., Prince, B., and Wright, H. K. (1952). A study of facial asymmetry.Journal of Personality 21: 68–84.
Lynn, J. G. (1940). An apparatus and method for stimulating, recording and measuring facial expression.Journal of Experimental Psychology 27: 81–88.
Lynn, J. G., and Lynn, D. R. (1938). Face-hand laterality in relation to personality.Journal of Abnormal and Social Psychology 83: 291–322.
Lynn, J. G., and Lynn, D. R. (1943). Smile and hand dominance in relation to basic modes of adaptation.Journal of Abnormal and Social Psychology 38: 250–276.
Mandal, M. K., Asthana, H. S., Madan, S. K., and Pandey, R. (1992). Hemifacial display of emotion in the resting face.Behavioral Neurology 5: 169–171.
Mandal, M. K., Asthana, H. S., and Tandon, S. C. (1993). Judgment of facial expression of emotion in unilateral brain-damaged patients.Archives of Clinical Neuropsychology 8: 171–183.
Mandal, M. K., and Singh, S. K. (1990). Lateral asymmetry in identification and expression of facial emotions.Cognition and Emotion 4: 61–70.
McGlone, J. (1980). Sex differences in human brain asymmetry: A critical survey.The Behavioral and Brain Sciences 3: 215–263.
Miehlke, A. (1973).Surgery of the Facial Nerve, W. B. Saunders, Philadelphia, PA.
Monserrat, L. (1984).Facial asymmetry in the spontaneous expression of emotion: An index of the role of functional brain asymmetry in the regulation of emotional expression. Unpublished doctoral dissertation, New York University, New York.
Moreno, C. R., Borod, J., Welkowitz, J., and Alpert, M. (1990). Lateralization for the expression and perception of facial emotion as a function of age.Neuropsychologia 28: 199–209.
Moscovitch, M., and Olds, J. (1979, June).Asymmetries in spontaneous facial expressions and their possible relation to hemispheric specialization. Paper presented at the European International Neuropsychological Society, Amsterdam, The Netherlands.
Moscovitch, M., and Olds, J. (1982). Asymmetries in spontaneous facial expressions and their possible relation to hemispheric specialization.Neuropsychologia 20: 71–81.
Myers, R. F. (1976). Comparative neurology of vocalization and speech: Proof of a dichotomy.Annals of the New York Academy of Sciences 51: 112–129.
Rappeport, M., and Friendly, M. (1978).Facial asymmetry in emotion: Observer and stimulus differences. Paper presented at the Canadian Psychological Association, Ottawa, Canada.
Remillard, G. M., Andermann, F., Rhi-Sausi, A., and Robbins, N. M. (1977). Facial asymmetry in patients with temporal lobe epilepsy.Neurology 27: 109–114.
Rinn, W. B. (1984). The neuropsychology of facial expression: A review of the neurological and psychological mechanisms for producing facial expression.Psychological Bulletin 95: 52–77.
Rinn, W. E., Friedman, C., and Meller, P. (1982, February).An investigation of personality correlates of lateral gaze preference and facial asymmetry. A paper presented at the meeting of the International Neuropsychological Society, Pittsburgh, PA.
Roberts, L. (1966). Central brain mechanisms in speech. In Carterette, E. C. (ed.),Brain Function: Speech, Language and Communication, University of California Press, Berkeley, CA, pp. 17–36.
Ross, E. D., Homan, R. W., and Buck, R. (1994). Differential hemispheric lateralization of primary and social emotions.Neuropsychiatry, Neuropsychology, and Behavioral Neurology 7: 1–19.
Rozhe, A., Voronin, L. G., and Sokolov, Ye. N. (1960). Electroencephalographic research on temporary association with dampening of the orientation reflex in man. In Brazier, M. A. B. (ed.),The Central Nervous System and Behavior: Translations from the Russian Literature, The Josiah Macy, Jr., Foundation, Bethesda, MD, pp. 841–859.
Sackeim, H. A., and Grega, D. M. (1987). Perceiver bias in the processing of deliberately asymmetric emotional expressions.Brain and Cognition 6: 464–473.
Sackeim, H. A., and Gur, R. C. (1978). Lateral asymmetry in intensity of emotional expression.Neuropsychologia 16: 473–481.
Sackeim, H. A., and Gur, R. C. (1980). Asymmetry in facial expression.Science 209: 834–836.
Sackeim, H. A., and Gur, R. C. (1983). Facial asymmetry and the communication of emotion. In Cacioppo, J. T., and Petty, R. E. (eds.),Social Psychophysiology, Guilford, New York, pp. 307–352.
Sackeim, H. A., Weiman, A. L., and Forman, B. D. (1984). Asymmetry of the face at rest: Size, area and emotional expression.Cortex 20: 165–178.
Schiff, B. B., and Lamon, M. (1989). Inducing emotion by unilateral contraction of facial muscles: A new look at hemispheric specialization and the experience of emotion.Neuropsychologia 27: 923–935.
Schiff, B. B., and MacDonald, B. (1990). Facial asymmetries in the spontaneous response to positive and negative emotional arousal.Neuropsychologia 28: 777–785.
Schnierla, T. (1959). An evolutionary and developmental theory of motivation underlying approach and withdrawal.Nebraska Symposium on Motivation 7: 1–42.
Schwartz, G. E., Ahern, G. L., and Brown, S. (1979). Lateralized facial muscle response to positive and negative emotional stimuli.Psychophysiology 16: 561–571.
Seinen, M., and Van Der Werff, J. J. (1969). The perception of asymmetry in the face.Nederlands Tijdschrift voor de Psychologie en Haar Grensgebieden 24: 551–558.
Sergent, J., Ohta, S., and MacDonald, B. (1992). Functional neuroanatomy of face and object processing.Brain 115: 15–36.
Silberman, E. K., and Weingartner, H. (1986). Hemispheric lateralization of functions related to emotion.Brain and Cognition 5: 322–353.
Sirota, A. D., and Schwartz, G. E. (1982). Facial muscle patterning and lateralization during elation and depression imagery.Journal of Abnormal Psychology 91: 25–34.
Skinner, M., and Mullen, B. (1991). Facial asymmetry in emotional expression: A meta-analysis of research.British Journal of Social Psychology, 30: 113–124.
Sperry, R. W. (1966). Brain bisection and consciousness. In Eccles, J. C. (ed.),Brain and Conscious Experience, Springer-Verlag, New York, pp. 298–313.
Strauss, E., and Kaplan, E. (1979).Lateralized asymmetries in self-perception. Paper presented at the Canadian Psychological Association, Quebec, Canada.
Strauss, E., and Kaplan, E. (1980). Lateralized asymmetries in self-perception.Cortex 16: 289–293.
Strauss, E., Moscovitch, M., and Olds, J. (1980).Children’s production of facial expression. Paper presented at the convention of the American Psychological Association, Montreal.
Stringer, P., and May, P. (1981). Attributional asymmetries in the perception of moving, static, chimeric and hemisected faces.Journal of Nonverbal Behavior 5: 238–252.
Thompson, J. K. (1985). Right brain, left brain; left face, right face: Hemisphericity and the expression of facial emotion.Cortex 21: 281–299.
Tschiassny, K. (1953). Eight syndromes of facial paralysis and their significance in locating the lesion.Annals of Otology, Rhinology and Laryngology 62: 677–691.
Tucker, D. M. (1981). Lateral brain function, emotion, and conceptualization.Psychological Bulletin 89: 19–46.
Tucker, D. M. (1986). Neural control of emotional communication. In Blanck, P. D., Buck, R., and Rosenthal, R. (eds.),Nonverbal Communication in the Clinical Context, The Pennsylvania State University Press, University Park, PA, pp. 258–307.
Tucker, D. M., and Frederick, S. L. (1989). Emotion and brain lateralization. In Wagner, H. L., and Manstead, A. S. R. (eds.),Handbook of Social Psychophysiology, Wiley, New York, pp. 27–70.
Tucker, D. M., and Williamson, P. A. (1984). Asymmetric neural control systems in human self-regulation.Psychological Review 91: 185–215.
Van Gelder, R. S., and Van Gelder, L. (1990). Facial expression and speech: Neuroanatomical considerations.International Journal of Psychology 25: 141–155.
Wemple, C. Y., Safer, M. A., and Notarius, C. T. (1986, August).Display rules and facial expression: Intensity, asymmetry and type. Paper presented at the convention of the American Psychological Association, Washington, DC.
Wolff, W. (1933). The experimental study of forms of expression.Character and Personality 2: 168–173.
Wolff, W. (1943).The Expression of Personality: Experimental Depth Psychology, Harper and Row, New York.
Woodworth, R. S., and Schlosberg, H. (1954).Experimental Psychology, Holt, Rhinehart, and Winston, New York.
Wyler, F., Graves, R., and Landis, T. (1987). Cognitive task influence on relative hemispheric motor control: Mouth asymmetry and lateral eye movements.Journal of Clinical and Experimental Neuropsychology 9: 105–116.
Wylie, D. R., and Goodale, M. A. (1988). Left-sided oral asymmetries in spontaneous but not posed smiles.Neuropsychologia 26: 823–832.
Author information
Authors and Affiliations
Additional information
An earlier version of this paper by the first author was presented at the XV Annual Symposium of the Society of Craniofacial Genetics, July 12, 1992, Stanford University, Palo Alto, CA.
Rights and permissions
About this article
Cite this article
Borod, J.C., Haywood, C.S. & Koff, E. Neuropsychological aspects of facial asymmetry during emotional expression: A review of the normal adult literature. Neuropsychol Rev 7, 41–60 (1997). https://doi.org/10.1007/BF02876972
Issue Date:
DOI: https://doi.org/10.1007/BF02876972