Reason to smile: Happiness is the most dominant human expression, study finds

COLUMBUS, Ohio — Smile, and the whole world smiles with you. A new Ohio State University study has determined that of the thousands of possibilities, there are but 35 universally accepted facial expressions. Yet perhaps most remarkable is that roughly half of these, 17 to be exact, are expressions of happiness.

Unless we are actors, most of us are probably unaware of the myriad ways our faces can be reconfigured to express emotions, whether voluntarily or involuntarily. It turns out, however, humans are meant to smile much more often than they grimace, scowl, frown or wince.

“This was delightful to discover,” says study coauthor Aleix Martinez, a cognitive scientist and a professor of electrical and computer engineering at the university, “because it speaks to the complex nature of happiness.”

The current study is an expansion of previous research by the same study authors, which found that humans are able to correctly determine other people’s emotions about 75 percent of the time simply by observing blood flow changes around the nose, eyebrows, cheeks and chin.

For the current study, researchers created a list of 821 words to describe feelings and had these translated into other languages to download images across multiple cultures. With 7.2 million images of facial expressions from 31 countries, scientists used computer algorithms to discover that the human face can combine different muscles in different ways to express itself in 16,384 unique ways.

When they sorted all these thousands of expressions into categories, the study authors expected to find several hundred variations of emotions. Instead, they were surprised to find only 35.

“We were shocked,” Martinez said. “I thought there would be way, way more.”

Because of the narrow results, researchers thought perhaps most expressions were culture-specific. They analyzed the same data set of 7.2 million images and instead found just eight primary expressions. They concluded that most facial expressions are understood by all, and about half of these expressions are used to express joyfulness. The study found that happiness, whether expressed in a contented smile, glowing cheeks or crinkly eyes, is the face other humans find most recognizable.

Researchers note that there are three expressions for fear, four for surprise and five each for sadness and anger. Disgust has only one expression.

“Happiness acts as a social glue and needs the complexity of different facial expressions,” explains Martinez. “Disgust is just that: disgust.”

So go ahead and put your best face forward. If it seems that smiling comes easiest, now you know that perhaps that’s because it’s supposed to be.

The study is published in the Jan. 14, 2019 online journal IEEE Transactions on Affective Computing.