The Face Function

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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 disgustFear 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.”

TheScream

About the author

Sam McDougle

SAM MCDOUGLE is a Ph.D. candidate in Psychology and Neuroscience at Princeton University. His writing has appeared in Vice and The Atlantic.

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10 Comments

  • The news channel I watch has started bringing in “experts” in facial expressions. They examine the politician in the video and tell us, he’s nervous, she’s trying to mislead, trying to hold back anger… When a politician can’t hide their purpose, we can all gain.
    We communicate many ways, but we also effect our own body with our expressions. There are groups of people that get together and make themselves laugh. There may be nothing funny, but you can still smile and even simulate the laughing process. They claim to feel better and are healthier.

  • Interesting post.
    Larry: I don’t know about you, but the ‘facial experts’ on tv always seem pretty bogus to me!
    Sam – A few comments:
    1. The Paul Ekman article is interesting, but I think it glosses over cultural differences in facial expression too fast. It’s possible that some expressions are more involuntary while others are more socialized, especially when taking into account cultural nuances like eye contact.
    2. How would you respond to the argument that so many of our near-primate relatives (chimps etc.) use ‘smiling’ and the showing of teeth as a sign of aggression? A monkey grinning at you is definitely not a sign of happiness!
    3. How would this tie in to people who fall on the Autism spectrum? For many people on the spectrum, expressing (interpreting, especially) facial expressions is very difficult

  • Jeremy,
    I await Sam’s response to your comments, but just to throw in my two cents in response to #2:
    I can make a pretty scary showing-of-teeth grin. Definitely not a friendly look. I think a “friendly” grin has as much to do with the rest of the facial muscles as it does the showing of teeth, and this could be the case for our primate relatives as well.
    I have no science to back this up. But I’ll give a demonstration if needed.

  • Jeremy –

    thanks for your thoughtful comment.
    a few words:

    1. Ekman alludes (perhaps too briefly) to cultural differences in his brief description of his 1969 work comparing Japanese and American subjects and disgust vs. disgust-masking expressions. He found differences only when an authority figure was present (pg 32). I would argue that certain cultural pressures (and eye contact may very well be one of these) have the power to override natural dispositions in this way. In other words, i don’t think expressions are either “socialized” or “involuntary,” i think they are all innate but can be molded by social factors. The base expressions are universal, though their manifestations in varying social settings are subject to some degree of change.
    2. I defer to Noah and Robby on this one, with the added caveat that there are often major differences in very closely related species in regard to socially relevant behaviors (like aggression or affection)…i.e. the large mating behavior differences btw. gorillas and chimps.
    3. The autism point is a very very interesting one, and I was torn about whether or not to bring it up in my post. I think the key here is, as you mentioned, that the more significant disability among autistics is the interpreting of facial expressions. Actually, the fascinating divergence between expressing and interpreting facial expressions is supported by some interesting neurophysiological data. According to Simon Baron-Cohen (google his book “Mindblindness” – perhaps the best literature on autism around), the inability for most autistics to “read” the faces of their peers has to do with problems in “theory of mind,” which is a proposed psychological module that helps one attribute goals, beliefs, and desires to other individuals. TOM is distinct from the neural substrates that produce expressions, which helps explain the divergence. However, because more serious cases tend to have trouble with producing certain emotional expressions themselves, this idea does not cover all the bases.

    Thanks for reading!

  • Good points, all.
    I guess my discomfort with Ekman’s claim that facial expressions are universal is due to my own caution towards explanations that seem too reductionist at first glance.
    I haven’t heard of Simon Baron-Cohen (Related to Sacha? They are both British!) but I’ll keep my eye open for that book you mentioned.
    As for the chimp-smiling, I was under the impression that they usually ‘smile’ to show their teeth, since biting is their main form of attack. But I think Noah’s right – it’s probably more than just the teeth that make a smile. I await anxiously his demonstration the next time I see him!

  • Almost all public ‘actors’, by which I mean, those with a community exposure: workplace, media, instituional setting, share a common skill: facial manipulations that belie intention. I would think that one should worry less about true responsive expressions, regardless of cultural interpretation, and instead focus upon manipulation by false fronts. Television demonstrates best what I have in mind: women use their ‘teeth’ showing such good will to the world. I’ve come to despise good looking teeth simply because I often suspect the motives of the actor. Somehow cosmetics have evolved to avoid reality, so in the Western framework I’m not so sure what good it does us to have a neuronal catalogue of expression…unless fraud has a universal display.

  • I find myself laughing at horror films most of the time. It’s usually because what’s happening is so over the top ridiculous that I’m laughing in sort of a, “Yeah, like that would happen.” kind of way, or laughing at myself for being scared by something I know is fake.

    I have Asperger’s Syndrome, while some people say those with Autism have impaired empathy, I don’t believe that. I am genuinley horrified when something bad happens to someone in a horror film. Yet there are many horror films that play on dark humor, like the original Friday the 13th films. So most of the time I fnd horror films funny, because they go to such an extreme of ridiculousness.

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