Certain smiles aren't all they're cracked up to be

March 1, 2018, Bar-Ilan University
Certain smiles aren't all they're cracked up to be
Physically distinct smiles solve different social tasks. Reward smiles (left) reinforce desired behavior by signaling positive feelings; affiliation smiles (center) promote approachability by signaling non-threat; dominance smiles (right) influence social hierarchies by signaling superiority. Images are of DiMonte Henning (above) and Marcus Jahn (below). Credit: Jared D. Martin and Magdalena Rychlowska

Sweaty palms, a racing heart, a faltering voice. Many people find public speaking unpleasant. The mere anticipation of social evaluation increases the activity of almost all body systems related to stress, with particularly strong activation in the hypothalamic-pituitary-adrenal (HPA) axis, the human body's central stress response system.

How does the HPA axis respond to feedback we receive from others in these social situations? Positive or negative verbal feedback in response to a speech, such as "that was/wasn't good", is known to activate the HPA axis. But until now little scientific inquiry has been conducted into how our bodies respond to purely nonverbal feedback, such as facial expressions.

A new study of nonverbal feedback, published today in Scientific Reports by researchers from the University of Wisconsin-Madison and Bar-Ilan University, finds that smiles may reduce or increase physical stress depending upon how they are perceived. Jared D. Martin, Heather Abercrombie and Paula Niedenthal, of the University of Wisconsin-Madison, and Eva Gilboa-Schechtman, of Bar-Ilan University, demonstrate that smiles with different social functions have different effects on HPA axis activity when they are perceived as evaluative feedback in stressful social situations.

The researchers measured in the saliva of 90 male undergraduate students as an indicator of HPA axis activity. They discovered that 'dominance' smiles, which challenge social standing and signal disapproval, were associated with higher HPA activity, such as increases in heart rate and salivary cortisol. Individuals perceiving 'dominance' smiles also took longer to return to their baseline cortisol levels after the stressful event. These physical responses to 'dominance' smiles mirror the influences of negative verbal feedback.

By contrast, 'reward' and 'affiliation' smiles, which reinforce behavior, signal lack of threat and facilitate or maintain social bonds, respectively, exerted influences similar to the effects of displays of friendliness and positive social evaluation and buffered physiological activity.

The authors also found that individuals with higher heart-rate variability - the variation in the time between each heart beat - showed more nuanced responses to different smiles. Higher heart-rate variability - an index of parasympathetic nervous system activity - is positively associated with facial expression recognition accuracy.

"The findings provide further evidence for the view that smiles do not necessarily constitute positive nonverbal feedback, and that they may impact social interactions by affecting the physiological reaction of people who perceive them. In addition, cortisol appears to support the detection of social threat and coordinate biological activity needed to adequately respond to the threat," wrote the researchers. They also noted that the findings contribute to growing evidence of individual differences in sensitivity to the meaning of facial expression.

The authors caution that the small sample of exclusively male participants limits the generalizability of the findings. Further research is needed to explore if men and women respond differently to the same kind of , and to test the physiological effects of more overtly negative .

Explore further: Researchers crack the smile, describing three types by muscle movement

More information: Jared D. Martin et al, Functionally distinct smiles elicit different physiological responses in an evaluative context, Scientific Reports (2018). DOI: 10.1038/s41598-018-21536-1

Related Stories

Researchers crack the smile, describing three types by muscle movement

July 27, 2017
The smile may be the most common and flexible expression, used to reveal some emotions, cover others and manage social interactions that have kept communities secure and organized for millennia.

Facial models suggest less may be more for a successful smile

June 28, 2017
Research using computer-animated 3D faces suggests that less is more for a successful smile, according to a study published June 28, 2017 in the open-access journal PLOS ONE by Nathaniel Helwig from the University of Minnesota, ...

People anticipate others' genuine smiles, but not polite smiles

June 12, 2013
Smile and the world smiles with you—but new research suggests that not all smiles are created equal. The research shows that people actually anticipate smiles that are genuine but not smiles that are merely polite. The ...

Psychology prof studies what's behind candidates' smiles

October 23, 2012
As she was watching the first presidential debate, psychology Professor Paula Niedenthal couldn't help but notice something odd about Barack Obama's smile.

Grin and bear it -- smiling facilitates stress recovery

July 30, 2012
Just grin and bear it! At some point, we have all probably heard or thought something like this when facing a tough situation. But is there any truth to this piece of advice? Feeling good usually makes us smile, but does ...

Recommended for you

Some gut feelings are a red flag, according to research

March 21, 2018
Are you guided by gut feelings?

Treating depression in cancer increases quality of life, but not length of life

March 21, 2018
Researchers have found that treating depression doesn't make cancer patients live longer, but it does make lives immeasurably better.

20-year study finds little change in social functioning in people with psychosis

March 21, 2018
Researchers have found that levels of social impairment in people with schizophrenia remained remarkably stable in the years after the first hospitalisation for psychosis.

We start caring about our reputations as early as kindergarten

March 20, 2018
Kindergarteners don't use social media, but they do care about their public image. Research suggests that by the time kids go to elementary school, they're thinking critically about their reputation. In a Review published ...

We can read each other's emotions from surprisingly tiny changes in facial color, study finds

March 19, 2018
Our faces broadcast our feelings in living color—even when we don't move a muscle.

Social media use at age 10 could reduce wellbeing of adolescent girls

March 19, 2018
Social media use may have different effects on wellbeing in adolescent boys and girls, according to research published in the open access journal BMC Public Health.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.