According to a review of previous studies, published in the Psychological Bulletin, emotional facial expressions — such as smiling — can influence our emotional experience; however, the size of these effects varies and tends to be small.

“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, Ph.D. student in the Department of Psychology at the University of Tennessee, Knoxville.

“But psychologists have actually disagreed about this idea for over a century.”

These disagreements became more pronounced in 2016, when scientists 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. 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,” Coles said.

Coles and his colleagues from the University of Tennessee, Knoxville and Texas A&M University analyzed data from 138 studies involving more than 11,000 participants from all around the world.

The researchers found that 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.

“A lot of people think that you can smile your way to happiness, but these effects don’t really seem to be that powerful,” Coles said.

“We don’t think smiling is a quick fix for depression. Facial expressions like smiling can sometimes influence our emotions but not always.”

“We really still have a lot to learn about how these effects work, but they are worth studying because they provide a clue about how the mind and the body interact to shape our conscious experience of emotions.”

“Every day that we study these facial feedback effects, we get a little bit closer to understanding how emotions work, and that’s the real reason to smile.”

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Nicholas A. Coles et al. A meta-analysis of the facial feedback literature: Effects of facial feedback on emotional experience are small and variable. Psychological Bulletin, published online April 11, 2019; doi: 10.1037/bul0000194