The human smile is a powerful thing. To elevate mood, inspire empathy, or calm a fast-beating heart, you don’t need a gleaming row of perfect pearly whites. One YouTube baby-laugh video is enough to demonstrate that even an entirely toothless smile is a wonder-worker.

Researchers who study the effects of human smiles know that the Duchenne smile is among the most influential of human expressions.

A Duchenne smile is the one that reaches your eyes, making the corners wrinkle up with crow’s feet. It’s the smile most of us recognize as the most authentic expression of happiness.

Non-Duchenne smiles shouldn’t necessarily be considered “fake,” however. A more accurate way of describing them might be “polite.”

Polite smiles can communicate social pleasantness, and they can even signal discreet psychological distance, which may be an appropriate response in many situations.

A Duchenne smile is produced by the joint action of two facial muscles. The zygomaticus major muscle lifts the corners of your mouth while the orbicularis oculi raises your cheeks, causing the subsequent laugh lines at the outside corners of your eyes.

This kind of smile is named for Guillaume Duchenne, a 19th-century scientist whose major contributions center on mapping the muscles of the human body, including the muscles that control facial expression.

Charles Darwin discussed the Duchenne smile, noting, as many researchers have since confirmed, that it’s the constriction of the eyes that marks the smile of true enjoyment.

Duchenne controversy

Duchenne developed an early biopsy device he called a “histological harpoon,” as well as an electrical device that stimulated contractions of muscles so he could study their movements.

He conducted some of his experiments on mental health patients and on the severed heads of executed criminals.

They can elevate your mood

Smiling has been shown to change how you actually feel. Studies in the field of facial feedback show that information from the muscles in your face can influence your emotional state.

MRI scans also showed that engaging the muscles you use to smile stimulates parts of your brain that control emotional responses.

But what about the Duchenne smile? Does it have particular power over emotion?

A 2019 study seems to indicate that it does. Researchers measured the impact of Duchenne smiling among young people who felt ostracized socially, and they concluded that the participants could “spontaneously regulate their emotional experience” during these difficult social encounters.

They can help us connect

Neurobiologist Peggy Mason explored the effect of smiles, finding that they can be contagious. They’re one of many facial expressions that, when shared, create a kind of “social cohesion” that enables us to feel empathy and help one another to survive.

When one person — in homeroom, in a Zumba class, or in a virtual meeting between remotely working colleagues — looks at another and smiles, a brief bond is formed. In a world where digital social interactions may mean more loneliness, that real-life, real-time human connection has power.

They can change your body’s stress response

A 2012 group of researchers gave study participants two sets of stressful tasks, instructing some groups to maintain smiles throughout the experiment’s stressful phases. They even gave the smile groups chopsticks to hold in their teeth to simulate smile-like muscle responses.

They found that heart rates among the smiling group stayed the lowest during stress recovery, with the calmest hearts being participants who had Duchenne smiles.

The study’s authors concluded that, “there are both physiological and psychological benefits from maintaining positive facial expressions during stress.”

They shape how others see you

Numerous studies have shown that smiling with your eyes as well as your mouth can help you be perceived as trustworthy and sincere, which could be helpful in any number of fields.

Studies also show that a Duchenne smile is quite persuasive. In fact, Duchenne smiles are often associated with positive customer service experiences, and they may even get you better tips in service industry jobs.

Scientists used to believe it was impossible to fake a Duchenne smile, but we now know otherwise. Some super-skilled communicators can produce a Duchenne smile intentionally.

And if you can produce a genuine smile as a matter of intent, maybe you should start practicing. Beloved Zen master and peace activist Thich Nhat Hanh once observed, “Your joy can be the source of your smile, but sometimes, your smile can be the source of your joy.”

The Duchenne smile is an expression that signals true enjoyment. It occurs when the zygomaticus major muscle lifts the corners of your mouth at the same time the orbicularis oculi muscles lift your cheeks and crinkle your eyes at the corners.

This kind of smile influences how other people see you: Duchenne smiles make you seem trustworthy and generous, which may make people respond positively to you in a variety of settings.

Smiling with your eyes and your mouth can lift your mood, calm you down, and help you forge connections with other people. And yes, you can create a Duchenne smile intentionally, to influence your own body and mind or to influence other people’s impressions.