Research from the University of Wisconsin-Madison has demonstrated that a smile is not always a pleasant expression with warm feelings behind it, and smiles can even be downright hateful. According to the study authors, recipients have physical responses which depend on the intended message behind the smile.
For example, some smiles are meant to express a message of dominance. These smiles cause their recipients to experience a spike in stress hormones. Smiles that are intended to be encouraging or rewarding, on the other hand, seem to protect people from feelings of stress.
“Facial expressions really do regulate the world. We have that intuition, but there hasn’t been a lot of science behind it,” said lead author Jared Martin. “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.”
Martin worked in the lab of Psychology professor and study co-author Paula Niedenthal. Her previous research on emotions resulted in three major types of smiles: dominance, which is meant to convey status; affiliation, which communicates a bond and shows you are not a threat; and reward, a big smile that is given to let someone know they are making you happy.
The investigation was focused on 90 male college students who were tasked with short, improvised speaking assignments. They were told they were being judged by a fellow student via webcam, who had actually been previously recorded while randomly expressing one of the three types of smiles.
Throughout the presentations, the students’ heart rates were monitored and they were asked to give saliva samples, which were used to measure levels of the stress hormone cortisol.
“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,” said 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 affiliate smiles were found to have an effect on the speakers that was similar to the effect associated with reward smiles.
The study is published in the journal Scientific Reports.