Scientists have found that different types of smiling positively affect an individual’s ability to recover from episodes of stress. They investigated whether manipulation of facial expressions would influence cardiovascular and affective responses to stress and found that study participants who were instructed to smile had lower heart-rate levels after recovery from stressful activities than participants who adopted neutral facial expressions, even if participants were not aware of their smile.

The study was conducted by researchers at the University of Kansas with 170 healthy participants between 18 and 25 (66 percent female and 44 percent male). The participants were divided into three groups and instructed to hold chopsticks with their teeth in a distinct manner in order to produce a neutral expression, a standard smile or a genuine Duchenne smile — named after the French neurologist Guillaume-Benjamin Duchenne.

For the latter, chopsticks were pushed sideways far back in the mouth so that both zygomaticus major and orbicularis oculi muscles (cheek and eye muscles) were engaged. In the standard smile group, chopsticks were held more firmly at the tip to activate cheek muscles only. The participants in the neutral group held the chopsticks lightly at the tip, activating as few facial muscles as possible, according to Sarah Pressman, assistant professor of psychology at the university.

In the second phase of the experiment, the participants completed a two-minute mirror star-tracing task, a stress-inducing task that required the participants to place their non-dominant hand inside a box and trace the lines of a star without going off the outline while only being able to see a mirror image. Afterwards, the participants completed a cold pressor test, a cardiovascular test, where a hand was submerged in ice water for one minute. All activities were performed while holding the chopsticks in their mouths.

Throughout the experiment, the researchers measured heart rate and self-reported stress level and found that the smiling groups showed lower heart-rate levels during recovery from the tasks, compared with participants in the neutral group. “Duchenne smiling was particularly advantageous, indicating that sincere smiles may be more effective for stress recovery than standard smile expressions, according to the study,” the researchers concluded.

In order to determine whether benefits are also present when awareness of facial expression is absent, half of the group members in each smiling group were not explicitly told to smile but also held the chopsticks in a manner that forced them to. The researchers observed that they too reported positive effects compared with those with neutral expressions although they were not aware of their smiles.

“These findings show that smiling during brief stressors can help to reduce the intensity of the body’s stress response, regardless of whether the person actually feels happy,” the researchers concluded.

The study will be published in the forthcoming issue of the Psychological Science journal.

Original Source: Dental Tribune

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