Mental Health

Your Smile Changes Stress Levels Of Those Who See it

There are many ways to read a smile, and they're not always positive. A new study suggests that our brains may be able to read the subtle differences between different types of smiles, which apparently affect our stress levels.

The newly published study on male college students revealed how friendly-looking smiles can be a buffer against stress, while smiles of dominance can led to an increase in stress hormones. The study was led by Jared Martin, a psychology graduate student at the University of Wisconsin–Madison. 

"Facial expressions really do regulate the world. We have that intuition, but there hasn’t been a lot of science behind it,” he said. “Our results show that subtle differences in the way you make facial expressions while someone is talking to you can fundamentally change their experience, their body, and the way they feel like you’re evaluating them."

Psychology professor Paula Niedenthal, a co-author of the study, had previously published research that established three types of smiles: dominance (conveying a social status), affiliation (communicating a bond to show you’re not a threat), and reward (a beaming, intuitive smile that lets others know they make you happy).

The new study is the first work to demonstrate that these different smiles have varying effects on the physiology of the recipient. Researchers gathered 90 male college students as participants, who were asked to spontaneously speak on a few topics while they were judged over a webcam by a fellow student. The evaluator, who was actually in on the study, smiled demonstrating dominance, reward or affiliation.

During this process, the researchers collected saliva samples from the participants to measure their levels of cortisol, a hormone that regulates numerous processes throughout the body such as metabolism and the immune response. Heart rates were also measured before, after and during the task.

So how did the recipients respond to each of the three smiles?  

"If they received dominance smiles, which they would interpret as negative and critical, they felt more stress, and their cortisol went up and stayed up longer after their speech," explained Niedenthal. "If they received reward smiles, they reacted to that as approval, and it kept them from feeling as much stress and producing as much cortisol."

The study added cortisol "appears to support the detection of social threat and coordinate biological activity needed to adequately respond to the threat."

It was also found participants with high heart-rate variability showed stronger physiological reactions to the different smiles. This meant those who had a longer period of time between heartbeats did not have extreme, varying reactions, compared to their counterparts.

Martin explained disorders like obesity, cardiovascular disease, autism, anxiety and depression can drag down heart-rate variability, weakening the ability to recognize and react to social cues. 

“Those things that we carry around with us change the way we perceive the world in very sensitive and personal ways,” he said.

While the study is limited by its sample size, it does lend support to understanding the physiology behind facial cues, and how these subtle, physical changes can affect social interaction.

The research was supported by the National Institutes of Health and National Science Foundation and U.S.-Israeli Binational Science Foundation.