Smiling really can make people feel happier, according to a new paper published in Psychological Bulletin.

Coauthored by researchers at the University of Tennessee, Knoxville and Texas A&M, the paper looked at nearly 50 years of data testing whether facial expressions can lead people to feel the emotions related to those expressions.

"Conventional wisdom tells us that we can feel a little happier if we simply smile. Or that we can get ourselves in a more serious mood if we scowl," said Nicholas Coles, UT PhD student in social psychology and lead researcher on the paper. "But psychologists have actually disagreed about this idea for over 100 years."

These disagreements became more pronounced in 2016, when 17 teams of researchers failed to replicate a well-known experiment demonstrating that the physical act of smiling can make people feel happier.

"Some studies have not found evidence that facial expressions can influence emotional feelings," Coles said. "But we can't focus on the results of any one study. Psychologists have been testing this idea since the early 1970s, so we wanted to look at all the evidence."

Using a statistical technique called meta-analysis, Coles and his team combined data from 138 studies testing more than 11,000 participants from all around the world. According to the results of the meta-analysis, facial expressions have a small impact on feelings. For example, smiling makes people feel happier, scowling makes them feel angrier, and frowning makes them feel sadder.

"We don't think that people can smile their way to happiness," Coles said. "But these findings are exciting because they provide a clue about how the mind and the body interact to shape our conscious experience of emotion. We still have a lot to learn about these facial feedback effects, but this meta-analysis put us a little closer to understanding how emotions work."