People wear a variety of smiles in their lifetimes — some revealing and others concealing. We smile when we win, and we grin to suppress chagrin. Thus did Herman Melville call the smile “the chosen vehicle for all ambiguities.”
A smile can be knowing, winning or false. It can stretch sly and toothy like a crocodile grin, or appear slight and enigmatic like the smirk on the Mona Lisa. Such a wide variety suggests a hitch in the old saw that it takes more muscles to frown than to smile: Which smile do they mean? A true smile — the kind that involves eye muscles that only 1 percent or so of humans can consciously control — probably takes quite a few more muscles than a frown, while a slight, we-are-not-amused, corners-of-the-mouth upturn takes the tug of only one or two pair.
Comparing “true” and “false” smiles fails to capture the full complexity of the question, however. Basic human emotions like anger, sadness, fear, surprise, disgust, contempt and happiness all produce recognizable expressions, but smiles can arise from a variety of emotional states — amusement, contentment, excitement, pride, satisfaction and relief, to name a few. Researchers disagree over whether each emotion maps to a particular arrangement of muscles, or whether one smile can stand for many feelings.
On the other hand, the old Joe Goodwin lyric, “When you’re smiling/The whole world smiles with you” is probably right on the money. Research suggests that people tend to greet smiles with smiles of their own, whereas frowns only draw return frowns about half the time.
Not only that, but smiles work in both directions: Just as happiness can make you smile, studies have shown that, thanks to a quirk of the autonomic nervous system, smiling can make you happy. Unfortunately, the same holds true for expressions of sadness and distress.
Both phenomena relate to mirror neurons — brain cells that spark up both when we observe an action, such as a smile, and when we take part in it.
Next time you feel blue, try a smile. Not only will people smile back, but you’ll trick your brain into feeling a little happier, too.
Sign up for the Live Science daily newsletter now
Get the world’s most fascinating discoveries delivered straight to your inbox.