Even a smile can cause a lot of stress

Facial expressions regulate the world

A smile is interpreted primarily as an act of kindness and warmth. But not every smile is positive. The human body reacts very differently to the different nuances of the smile. In a recent study, American scientists investigated the effects of smiles on the human body.

A research team headed by Jared Martin, a PhD in psychology from the University of Wisconsin-Madison, explores the physical responses that can bring a smile to the subject. A rewarding or warming smile can lower the stress level of the conversation partner and strengthen the bond. In contrast, a dominant, superior smile can result in an increase in stress hormones. The results of the study were recently published in the scientific journal "Scientific Reports".

Facial expressions regulate the world

"Our results show that subtle differences in the way facial expressions are used during a conversation can fundamentally change the body and mind of the conversation partner," Martin explains in a university press release on study findings. "Facial expressions really regulate the world," says Martin.

The main types of smile: dominance, affiliation and reward

Martin works closely with psychology professor Paula Niedenthal, whose emotion research has established three main types of smile: dominance, affiliation and reward. The dominant smile is supposed to convey its own status to its counterpart. The smile of belonging should strengthen the connection of the interlocutors and show that one does not pose a threat. The rewarding smile shows that you have made someone happy.

Course of the study

In the study, 90 subjects had to make short speeches via a webcam and saw the reactions of the audience on a screen. In fact, the reactions were pre-recorded reactions, each marked by a certain kind of smile, either reward, affiliation or dominance. In the meantime, the researchers monitored the heart rate of the speakers and regularly took saliva samples to measure the stress hormone cortisol.

Dominant smile caused stress

"If the subjects had a dominant smile, which they interpreted as negative and critical, they felt more stress," says Niedenthal. As a result, her cortisol levels also increased and remained elevated after the speech for a long time. In contrast, the rewarding smile was interpreted as approval and led to subjects feeling less stress and producing less cortisol. The corresponding smile could be interpreted more difficult by the subjects in this context, but came closer to the effect of the rewarding smile.

People deal differently with social information

"People differ in how tolerant or able they are to deal with or understand social information," says Niedenthal. Responsible for the reactions is the parasympathetic nervous system, which manages respiration and heart rate.

Diseases can change reactions

"Heart rate variability is not innate and unchangeable," explains Martin. Some diseases and disorders, such as obesity, cardiovascular disease, autism, anxiety and depression, can lower heart rate variability. This, in turn, could make people less aware of social signals such as dominance and reward and react differently to them.

Burdens change the perception

"We are all individuals: One may really be anxious, the other well in shape," sums up Martin. The things we carry around change the way we perceive the world in a very sensitive and personal way, according to the expert. (Vb)