The latest issue of Science Advances has a provocative and clever piece of research aimed at answering a long-standing question—one considered by Charles Darwin himself: are the facial expressions associated with human emotions universal across all cultures? And, if so, is that the result of evolution? The paper suggests that, at least for a limited set of emotions, the answer is yes to both questions. You can read the paper by clicking the screenshot below, or reading the pdf here. The full reference is at the bottom.
Cowen and Keltner note that there have been a fair number of attempts to answer this question, all involving going to remote areas where there is little contact with Westerners, and seeing if people in those areas match photos of Western expressive signals (joy, anger, sympathy) with similar words in their native language. The results have been mixed. That, one would think, already suggests that perhaps facial expressions aren’t universal. (Cultural similarities could be due to either cross-cultural transmission of expressivity, or to a common evolutionary heritage, but dissimilarities among different populations already suggest that culture can’t cause similarities.)
However, the authors suggest these tests are not dispositive, and suggest a better way to see if expressions are universal. What they did was to look at ancient Mesoamerican artworks that depict facial expressions associated with different situations, isolated the facial expressions, got modern observers to guess the emotions depicted, and then asked whether Westerners would judge those expressions to be ones appropriate to the situation depicted by the artwork. If there was a correlation between the judgements of which emotions were shown on faces, and those that other people guessed would appear in the situations depicted in the sculptures, this would suggest (but not prove) that expressions are not only universal, but perhaps universal because evolution made them universal.
The authors examined tens of thousands of Mesoamerican artifacts (going back to 1500 B.C.) archived by museums, and found 63 pieces of art that met their three criteria for this study:
- subjects were portrayed “within one of eight identifiable contexts” (torture, being held captive, carrying a heavy object, embracing another person, holding a baby, in fighting position, playing a ball sport, and playing music). Examples of each of these are given in the figure below.
- The facial expressions could be clearly visible.
- The artworks (sculptures and vessels) were deemed authentic by authorities.
Here are examples of the eight contexts for emotion; see the caption for details:
They then isolated the faces from the contexts so that the modern subjects could just look at the faces but not see what the subject was experiencing in the artwork. The 325 subjects were asked them to describe the facial expressions using 30 categories of emotion (e.g., “awe”, “anger”, “shame”, “fear”, and so on and 13 “affective features” like “arousal” and “dominance” (see categories in figure below).
Independently, they asked 114 different subjects, also modern Westerners, to judge what emotions they would expect someone to show in each of the eight situations above. These people were not shown the artworks but simply given the eight situations verbally and asked what emotions you’d expect people to evince. They then correlated the first subjects’ judgments on what emotions were portrayed by the faces with the expectation of what emotions should be shown from the eight situations, described in words, chosen for analysis.
Here are the correlations between the “read” of subjects from looking just at the faces with the emotions expected judged from subjects looking at the context described in words.
Correlations above zero are positive; that is, the expectations of what you’d feel aligned with the subjects’ “read” of the artworks’ faces. As you see, of the 32 emotion categories assessed, 27 had correlations above zero, which alone says something (if there were no correlation, roughly half of the values would be above zero and half below). More important, only six of the 27 positive correlations had standard errors that overlapped zero, or “no correlation”; the rest were statistically significant.
This shows that, in general, the emotions expected by people hearing about the eight contexts for the artwork were those actually discerned by people who looked at the faces of the artwork. And that means that the emotions we expect to see in a modern situation were those that people read from artwork of ancient civilizations. This is turn suggests that at least some facial expressions are “universal”, and people can read them fairly accurately, even in sculptures, as reflecting what people are feeling in a situation. Because these cultures were far removed from ours, this also suggests that the facial expressions weren’t culturally inherited across the ages—that is, we don’t learn the expressions to show determination or distress or the other emotions from others, but express them innately.
One could, I suppose, argue that the Incas and Mayans simply passed on their facial expressions culturally to us as their descendants, but that’s a big stretch since the route for that kind of cultural transmission is dubious: we’re not the descendants of these Mesoamericans. Alternatively, the expressions could have been culturally inherited from our mutual ancestor who lived at least 60,000 years ago when H. sapiens left Africa to populate the world. If you’re a blank-slater, that’s the argument you’d make.
But it seems more plausible to me that smiling and scowling and showing distress and pain are innate features of our behavior, though I can’t adduce hard evidence for it except that a). babies who haven’t been socialized to show facial expressions of joy or distress still show easily interpretable expressions, presumably before they’re socialized; b). other primates have readable facial expressions without our kind of culture; and c.) one can make a plausible evolutionary hypothesis that humans might have evolved to show expressions that other humans could read: “honest signals.” None of this adds up to a strong evolutionary-psychology argument, but one can agree, from the results above, that there is some universality across millennia in how humans show emotions on their faces.
Finally, the authors used a method called “principal preserved components analysis” to gather in one basket the main “dimensions” (combinations of emotions) that best explain the correlations shown above. From this they determined that three combinations of factors combine to explain at least five types of facial expressions on sculptures. Those expressions, the ones most easily seen as “universal, are these:
- “pain”, often in the context of torture
- “determination”/”strain”, in sculptures showing heavy lifting
- “anger”, usually in sculptures depicting combat
- “elation”, seen in “contexts of familial or social touch”, and
- “sadness”, as in being held captive after defeat.
The paper has other analyses, but these are the main conclusion. The authors also give several caveats, and you can have a look at those.
The tentative takeaway lesson is that, even after millennia, we can pretty accurately read the facial expressions of people from different cultures. That is, there are some universals, at least between ourselves and Mesoamericans, in the expression of emotions. Whether that be the result of cultural inheritance or a universal code for expression that resides in our DNA (or a combination of these factors) can’t yet be discerned, but I’m betting on a largely biological-determinism explanation. And so are the authors, at least judging from their final paragraph:
The present results thus provide support for the universality of at least five kinds of facial expression: those associated with pain, anger, determination/strain, elation, and sadness. These findings support the notion that we are biologically prepared to express certain emotional states with particular behaviors, shedding light on the nature of our responses to experiences thought to bring meaning to our lives.
Here are a few more faces and the contexts in which they appear (see paper for explanation), but I think you can guess pretty well.
Cowen, A. S. and D. Keltner. 2020. Universal facial expressions uncovered in art of the ancient Americas: A computational approach. Science Advances 6:eabb1005.