Facial Expression

Facial muscles are involved in the expression and communication of emotional states. They can be activated both voluntarily and involuntarily,1 so there is ample opportunity for a person to interfere with the expression of emotion in ways that serve personal goals. There is strong scientific evidence that different configurations of facial-muscle contractions are associated with what are often called basic emotions.2 Those emotions include anger, contempt, disgust, fear, happiness, surprise, and sadness. There is also evidence that other emotions can be identified on the basis of patterns of movement in facial and bodily muscles (for example, embarrassment3) and that distinctions can be made between genuine felt happiness and feigned unfelt happiness according to whether a smile (produced by the zygomatic major muscles) is accompanied by the contraction of the muscles (orbicularis oculi) that circle the eyes.4

Facial-muscle activity can be measured accurately by careful examination of the changes in appearance that are produced as the muscles cause facial skin to be moved.5 Trained coders working with video recordings can analyze facial expressions reliably, but it is extremely time-consuming (it can take hours to analyze a few minutes of video fully). Greatly simplified methods that focus only on the key muscle actions involved in a few emotions of interest and that are appropriate for real-time screening are being developed and tested. Some basic efforts to develop automated computer systems for analyzing facial expressions have also been undertaken,6 but the problems inherent in adapting them for real-world, naturalistic applications are enormous.7


W.E. Rinn, “The neuropsychology of facial expression: A review of the neurological and psychological mechanisms for producing facial expressions,” Psychological Bulletin 95(1):52-77, 1984.


P. Ekman, “An argument for basic emotions,” Cognition and Emotion 6(3-4):169-200, 1992.


D. Keltner, “Signs of appeasement: Evidence for the distinct displays of embarrassment, amusement, and shame,” Journal of Personality and Social Psychology 68(3):441-454, 1995.


P. Ekman and W.V. Friesen, “Felt, false and miserable smiles,” Journal of Nonverbal Behavior 6(4):238-252, 1982.


P. Ekman and W.V. Friesen, Facial Action Coding System, Consulting Psychologists Press, Palo Alto, Calif., 1978.


J.F. Zlochower, A.J. J. Lien, and T. Kanade, “Automated face analysis by feature point tracking has high concurrent validity with manual FACS coding,” Psychophysiology 36(1):35-43, 1999.


For example, according to a German field test of facial recognition conducted in 2007, an accuracy of 60 percent was possible under optimal conditions, 30 percent on average (depending on light and other factors). See Bundeskriminalamt (BKA), Face Recognition as a Tool for Finding Criminals: Picture-man-hunt, Final report, BKA, Wiesbaden, Germany, February 2007. Available in German at http://www.cytrap.eu/files/EU-IST/2007/pdf/2007-07-FaceRecognitionField-Test-BKA-Germany.pdf.

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