Certain Smiles Don’t Mean What You Think They Do

People communicate as much with their facial expressions and body language as they do with their words, but it turns out not all smiles are created equal. Published in the journal Scientific Reports, a study by researchers from the University of Wisconsin-Madison and Bar-Ilan University, finds that smiles may reduce or increase physical stress depending on how they are perceived. The hypothalamic-pituitary-adrenal (HPA) axis is the body’s central stress response system, and in this study, the scientists demonstrated that smiles with different social functions have different effects on HPA axis activity when they are perceived as evaluative feedback in stressful social situations. In one experiment they measured levels of the stress hormone, cortisol, in the saliva 90 male participants as an indicator of HPA axis activity. They discovered that “dominance” smiles, which challenge social standing and signal disapproval, were associated with higher HPA axis activity. Individuals perceiving ‘dominance’ smiles also took longer to return to their baseline cortisol levels after the stressful event. On the flip side, ‘reward’ and ‘affiliation’ smiles, which reinforce behavior, signal lack of threat and facilitate, or maintain social bonds made respondents act like they were responding to a display of friendliness or a positive social situation. Researchers write, “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” (EurekAlert!