The Face Function
The form and function of our facial expressions
Norman Bates is coming for Lila Crane.
Gripped with fear, Lila dashes to the cellar to escape the approaching madman, her eyes wide with panic, senses heightened. You, the observer, similarly emote, as if there was a dark deadly figure lurking around your living room, waiting for the right moment before he (or she…or in this case, he-she) strikes. But your expression soon transforms – when Lila discovers the mummified old lady in the cellar you gasp, or perhaps shriek in some kind of dissonant harmony with her, and then squint and wrinkle your nose. After all, that mummy is just plain disgusting.
If you haven’t seen Hitchcock’s horror masterpiece the above may sound like nonsense, though you can certainly empathize with the primary emotions expressed: fear, here initiated by impending violence; and disgust, elicited by the sight (and, perhaps, smell) of a mummified old woman. I can’t imagine responding to either of these situations with, say, a smile or a laugh (unless you have seen Psycho enough times that Hitchcock’s sharp eye and Bernard Herrmann’s famed score gives you the movie-nerd-giggles, in spite of the terrifying action on-screen).
Human facial expressions are universal. There is no culture that expresses fear with a blissful smile, no country whose denizens frown with laughter. The reason(s) why facial expressions are so culturally invariant are not fully understood. The conventional knowledge is that facial expressions play an important social role in terms of deciphering your peers’ desires, motivations, and beliefs, and are thus unchanging. It would be difficult for an individual to form normal social bonds if their expressions were unrecognizable. The maladaptivity of some kind of novel facial expressions would likely result in a disabled social life and would be a particularly short-lived evolutionary trait.
But why do our expressions physically look the way they do? Why is a smile upturned, a frown down? Why do we open our eyes in fear and close them in pleasure? One answer would be that facial expressions are social signals that have arbitrary physical properties and only mean what they do because we’ve given them their meaning – like articles of language or fashion trends. Joshua Susskind of the University of Toronto believes otherwise – his research reveals that we cringe in disgust and widen our face in fear because there are physical properties of those expressions themselves that may help us respond to the kind of situations that cause disgust or fear.
Susskind looked at the physical properties of these two easily rendered facial expressions – fear and disgust. Fear is associated with enhanced sensory exposure: eye lids open up, the brow raises, and the nasal passage is widened. Disgust is associated with the rejection of sensory stimulation: the eye lids close, the brow lowers, and the nasal passage is constricted. But these are just descriptive factors about the changes in facial “form” brought about by the two expressions – what about changes in function?
Respecting the evolutionary biology axiom “form fits function,” Susskind studied how actual sensory perception was altered by the onset of fear and disgust. He had individuals accurately “pose” both expressions along with a ‘neutral’ expression, and complete certain sensory tasks.
His hypothesis was supported – fear led to a widened, more complete visual field as opposed to the neutral condition; disgust led to a reduction of the visual field. Fear led to an increase in saccadic eye movements (which helps individuals “sample” their visual field more efficiently) while disgust showed a slight slowing of eye movements. Lastly, fear allowed more air through the nasal passage, disgust did the opposite. All of these results support the idea that fear may look the way it does because it is serving an important function for the individual – it “heightens” the senses and could facilitate the recognition of a potential threat (fear is, of course, a response to a “threat” of some kind, real or imagined). Disgust may look the way it does because it constricts certain senses – bad smells are indicators of noxious substances, and your body rightfully rejects potentially dangerous, unsightly things (like, say, mummified bodies or bacteria-infested food).
Ultimately, facial expressions may have evolved for the direct benefits they provide to the organism on which they’re displayed. Perhaps the physical properties of expressions were later co-opted for use in social interaction (evolution is remarkably klugey). More evidence is needed to support this assertion, as is usually the case for similar “adaptive” explanations, but it is a compelling one nonetheless. It also helps explain the universality of facial expressions – as ten toes help all humans balance and ten fingers help us grasp, fearful, alerted eyes help us spot looming dangers and a crumpled nose helps us avoid pestilence.
I look forward to a forthcoming explanation of the smile or the glare, and it would not surprise me if at least some facial expressions are purely social in function. That is certainly the case when it comes to facially-driven behaviors such as deceit. In being deceitful, we use the usually “honest” signal that is our face to be dishonest and manipulate others. Here, the function of the expression is not what it does for us directly, as when fear enhances our vision, but what its interpretation by others does for us in the future – it is a purely social tool.
And with that, Mr. Norman Bates will have the last word:
“I think I must have one of those faces you can’t help believing.”