Here’s why you shouldn’t assume someone is happy just because they’re smiling

No facial expression is as synonymous with happiness as the smile, and no smile instantly conjures up positive perceptions like the Duchenne Smile. You may be unfamiliar with its technical name, but everyone instantly recognizes a Duchenne smile when they see it. It’s the smile seen on the face of every children’s cartoon character, and the smile every suburban dad wants when he tells his kids to “smile and say cheese!”

A Duchenne smile is characterized by the fact that it influences the entire face; one’s cheeks lift and the corners of their eyes wrinkle. Now, whenever people see others displaying the “smiling eyes” that go hand in hand with a Duchenne smile, they usually assume that person is feeling genuinely happy.

Somewhat surprisingly, however, a new study from Carnegie Mellon University finds that these iconic smiles aren’t always an accurate indicator of how happy a person is feeling.

If anything, study authors say, a Duchenne smile is a much more precise gauge of smile intensity than anything else.

“I do think it’s possible that we might be able to detect how strongly somebody feels positive emotions based on their smile,” says study leader Jeffrey Girard, a former postdoctoral researcher at CMU’s Language Technologies Institute, in a release. “But it’s going to be a bit more complicated than just asking, ‘Did their eyes move?'”

The general idea of using smiles and other facial expressions to assess mood is a topic that carries some baggage among psychological circles. Many believe facial expressions provide a legitimate glimpse into one’s state of mind, while others aren’t so sure. Similarly, research on this matter has largely proven inconclusive. 

So, along with colleagues from the University of Pittsburgh and Binghamton University, the research team decided to conduct an experiment in hopes of attaining some clear answers. A total of 136 volunteers were gathered to participate, and each person agreed to have their facial expressions recorded as they completed a series of tasks designed to elicit various emotions (happiness, amusement, fear, embarrassment, etc). After finishing all the tasks, participants self-reported how strongly they felt each emotion.

Then, researchers used those recordings to create videos of all the participants’ smiles during the experiment. Those videos were shown to a group of new study subjects, who were asked to guess how happy each original volunteer was feeling based solely on their smile.

The resulting findings were telling. When participants reported feeling happy and smiled, 90% of the time they showed the “smiling eyes” indicative of a Duchenne Smile. But, Duchenne smiles also accounted for 80% of the smiles on subjects’ faces as they felt no reported positive emotions.

What does that tell us? Well, it means that a classic smile that lifts the cheeks and crinkles the eyes doesn’t always necessarily mean a person is feeling happy.

“It is really important to look at how people actually move their faces in addition to how people rate images and videos of faces, because sometimes our intuitions are wrong,” Girard adds.

“These results emphasize the need to model the subtleties of human emotions and facial expressions,” notes study co-author Louis-Phillippe Morency, associate professor in the LTI and director of the MultiComp Lab. “We need to go beyond prototypical expression and take into account the context in which the expression happened.”

Regarding the second group of volunteers who had been told to judge participants’ emotions based on their faces, as expected most guessed that those displaying a Duchenne smile were feeling pretty good.

This research set itself apart from earlier smile-centric projects by taking a continual video recording of subjects, as opposed to simply snapping individual pictures. Moreover, the experiment was designed to evoke genuine, spontaneous facial changes, not artificial smiles. Both of these factors are notable, as they strengthen the legitimacy of the conclusions drawn. 

At the end of the day, humans are just too complex to be defined by something as simple as a smile. Mental health is a much more accepted topic nowadays, and it’s often said that we can have no idea what’s going on in someone’s head on a day-to-day basis; their fears, worries, anxieties, etc. Similarly, accurately assessing someone’s positivity or happiness based on just their face feels more and more like a fool’s errand as we continue to understand the human psyche in greater detail.

The full study can be found here, published in Affective Science.