A smile is just a smile, right? Not so, according to researchers. Psychologists from the U.S. and the U.K. have figured out how to identify different types of smiles to better understand the popular facial expression. After all, when the corners of our mouths are turned up it doesn’t necessarily mean we’re feeling gleeful.
In the study, researchers asked participants to observe thousands of computer-generated expressions with random combinations of facial muscles activated, which included some action from the smile muscle, the zygomaticus. The authors then asked the volunteers to pinpoint when they recognized one of three expressions — smiles of reward, affiliation, and dominance — as well as when the expression wasn’t even a smile at all.
The formulas for each distinct smile, which are published in the journal Psychological Science, are as follows:
A reward smile is a symmetrical hoist of zygomaticus muscles, plus a dash of eyebrow lift and some sharp lip pulling. “Probably the most intuitive, the kind of smile you would use with a baby, so he will smile back or do things you like,” said study co-author Paula Niedenthal, a psychology professor at the University of Wisconsin–Madison, in a press release.
Affiliative smiles include a similar symmetrical upturn to the mouth, but spread wider and thinner with pressed lips and no exposed teeth. These are typically used to communicate tolerance, acknowledgment, or a bond, and show that you’re not a threat.
Dominance smiles dispense with the symmetry, pairing a bit of lopsided sneer with the raised brows and lifted cheeks typically associated with expressing enjoyment. This look signifies status.
“We now know which movements we should look for when we describe smiles from real life,” stated study co-author Magdalena Rychlowska, a postdoctoral researcher at Cardiff University. “We can treat smiles as a set of mathematical parameters, create models of people using different types of smiles, and use them in new studies.”
This research team is already looking into the way affiliative and dominance smiles can shift the outcome of games and negotiations. However, this isn’t the first study to examine the meaning behind a grin. In fact, the same investigators concluded in 2016 that smiles — and frowns — tend to be contagious since people have an instinct, whether conscious or unconscious, to mimic someone’s expression.
“Even though our mouths are one of the smaller things on our body, our smile sends one of the biggest messages,” Stacy Kaiser, psychotherapist, relationship expert, and editor-at-large for Live Happy, tells Yahoo Beauty. “It is a significant form of nonverbal communication that reveals happiness, disappointment, irritation, confidence, love, trustworthiness, and more.”
Kaiser commends the researchers for putting a spotlight on this common facial expression and hopes their findings will make others ponder their silent reactions.
“I have spoken with many people who send nonverbal cues and have absolutely no awareness of the message they are sending,” says Kaiser. “Perhaps each of us can pay more attention to the kind of smile we have on our face and the resulting message that is being delivered to others. Because whatever it is that we are revealing through our smile will impact another person’s judgment and perception.”
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