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The Danger of Not Reading a Face
The Danger of Not Reading a Face · Fortune

This week I found myself drawn to a research study entitled, “Experience-based human perception of facial expressions in Barbary macaques (Macaca sylvanus).” How, you wonder? Well truth be told, I spied a summary of the paper on the science news site Phys.org, which offered a much juicier title: “Tourists risk animal bites by misreading wild monkey facial expressions as ‘kisses.’” (As a rule, I’ll read anything with “wild monkey” in the headline.)

But the original research paper—and my follow-up conversation with the lead author, Laëtitia Maréchal—turned out to be more fascinating than even the phrase “wild monkey” might suggest.

The gist is that we humans are not so good at reading the facial expressions of Barbary macaques—and hint: this is important—even though we think we are.

In the study, Marechal, a behavioral ecologist/primatologist/conservation biologist at the UK’s University of Lincoln (it’s hard to know what to call a scientist with two Master’s degrees and a Ph.D.), and her colleagues showed volunteers photos of Barbary macaques displaying various “facial expressions related to aggressive, distressed, friendly or neutral states” and then tested their ability to identify them.

The humans really missed the mark when it came to matching a particularly toothy macaque expression—one in which “the corners of the lips are fully retracted and the upper and lower teeth are shown”—with the correct emotion. What looked to many like a smile was, in fact, a reflection of “a distressed emotional state…usually displayed as a submissive behavior during aggressive or dominant interactions.” Similarly, an expression that looked like “blowing kisses” was actually a sign of aggression. Oh well.

Marechal and her teammates conclude that this instinctive misreading may be getting both tourists and monkeys injured in places like South Africa’s Cape peninsula, Gibraltar, and various temples in Southeast Asia, where macaques and Ray-Ban-toting bipeds often get too close to one another.

But what makes the study truly compelling is that the research flies in the face of a very old theory, proposed by none other than Charles Darwin—that human beings and their close evolutionary cousins (in the words of Rachael E. Jack and colleagues) “communicate six basic internal emotional states (happy, surprise, fear, disgust, anger, and sad) using the same facial movements.” Indeed, that theory, called the universality hypothesis, has been getting beaten up over the last decade or so, with one research study after another taking an evidentiary swipe.