Facial expressions of intense joy and pain are indistinguishable

Eyes shut tight, face contorted into a grimace. Are they ecstatic or anguished? Ignorant of the context, it can be hard to tell. Recent research that involved participants looking at images of the facial expressions of professional tennis players supported this intuition – participants naive to the context were unable to tell the difference between the winners and losers.

From a scientific perspective, the problem with the tennis study is that the findings might have been affected by the players' physical exertion or their awareness of being on public display. To test the similarity of facial expressions of joy and pain more robustly, a new study in the journal Emotion has used videos taken from a much wider range of contexts.

Sofia Wenzler and her colleagues began by finding online videos of the ecstatic relatives of soldiers who'd just made a surprise return home. For comparison they found videos of witnesses caught up in real life terror attacks who were expressing intense negative emotion (none were actually harmed themselves).

The researchers took stills of the moment of peak emotional facial expression from the joyful and negative videos and presented them to 28 undergrad students. Naive to the context of the facial expressions, the students' task was to rate them from 1 "most negative" to 9 "most positive". On average, they rated the intense joy and intense anguish facial expressions negatively and to a similar extent. In other words, the students couldn't tell the difference between the facial displays of intense pleasure and pain.

A second experiment involving children's facial expressions produced largely similar results. This time, for the negative emotional displays, the researchers took stills from pranks shown on the Jimmy Kimmel late-night TV show, such as when children woke to discover their parents had eaten all their sweets earned through trick-or-treating. For children's facial expressions of intense joy, the researchers found online videos of children receiving surprise treats, such as tickets to see their favourite pop star in concert.

Again, students naive to the context looked at and rated still images of the children's facial expressions and again they rated intense joy negatively, although in this case not as negatively as intense pain (this might be because the contexts used in this experiment were not as momentous as those used in the first experiment that featured adults).

The findings from the two experiments contradict mainstream psychological theories of emotion, which predict that facial expressions of emotion should be most distinguishable at the opposite ends of the positive/negative spectrum. One explanation for this contradiction considered by the researchers is that in moments of extreme joy, people are actually experiencing negative emotion, for example through the evocation of negative memories. Another is that extreme joy prompts the expression of negative emotion as a way to restore emotional equilibrium. However, Wenzler and her team find both these possibilities unconvincing – for one thing, the equilibrium account predicts incorrectly that negative emotion should manifest in facial expressions of joy.

A matter on which the researchers remain silent is why, from an evolutionary perspective, humans have developed a tendency to express intense joy in a way that is perceived as indistinguishable from intense pain. This is pure speculation, but perhaps it is because for our ancestors, intense joy, like pain, was typically a moment of vulnerability, and it was adaptive for its facial expression to signal a need for support and protection.

Further reading

Wenzler, S., Levine, S., van Dick, R., Oertel-Knöchel, V., & Aviezer, H. (2016). Beyond Pleasure and Pain: Facial Expression Ambiguity in Adults and Children During Intense Situations. Emotion DOI: 10.1037/emo0000185