According to Darwin’s evolutionary theory The Expression of the Emotions in Man and Animals, “Disgust is a sensation rather more distinct in its nature, and refers to something revolting, primarily in relation to the sense of taste, as actually perceived or vividly imagined; and secondarily to anything which causes a similar feeling, through the sense of smell, touch, and even of eyesight.” (2) Darwin observed that we express extreme disgust by moving our mouths in a similar way to when we are about to vomit: We open our mouths wide, forcefully retract our top lips, screw up our noses, drop our bottom lips and turn them inside out.
Facial expressions of various emotions, including disgust, have been widely studied since the late 1950s. Psychologists Paul Ekman and Walter Friesen showed that such expressions are universal, and developed FACS, a Facial Action Coding System.(3)
According to this system, we express disgust by screwing up our noses (contracting the quad. Labii sup. aka the Levator labii superioris alaeque nasi) lowering the corners of our lips (via the Musculus depressor anguli oris) and opening our bottom lips (thanks to the Depressor labii inferioris muscle).
Disney-Pixar(5) followed this anatomical description to personify the emotion of Disgust in its film Inside Out(6).
Notes et références
(1) Rozin P et al (2008). Disgust. In Handbook of emotions, 3rd ed. (pp. 757-776). New York: Guilford Press.
(2) Darwin CR (1872) The expression of the emotions in man and animals. London: John Murray. 1st edition, 373pp. Citation on page 254. Accessible here
(3) Ekman P & Friesen WV (1976). Measuring facial movement. Env. Psycho.Nonverbal Behav., 1(1), 56-75. Available here.
Ekman P & Friesen WV (1978). Manual for the facial action coding system. Consulting Psychologists Press.
(4) Biehl et al (1997) J. Nonverbal Behav., 21(1), 3-21.
(5) Keltner D & Ekman P (2015). The Science of ‘Inside Out’, The New York Times, july 3 2015.. Available here.
(6) Video “Inside out | Meet Disgust | Disney Pixar” available here.