He isolated which muscles are behind our expressions of terror, sadness and joy.

While many muscles in our face can simulate a smile, only two produce a genuine smile--one under our eyes and another on the side of our cheeks.

It looks like your eyes are smiling, too.

Psychologists call this a Duchenne smile.

Joy and happiness make us genuinely smile, but can smiling make us genuinely happy?

Inspired by Duchenne’s work, Charles Darwin suggested that our facial movements influence our emotional experiences.

There’s a feedback loop, so looking scared would make you more fearful and a genuine smile would make you happy.

It’s called the “Facial Feedback Hypothesis”.

Skip forward a century, an American psychologist Paul Ekman monitored the smiles of a group of women while they watched a series of movies.

Those who smiled genuinely (a Duchenne smile) and moved those muscles near their eyes reported feeling significantly more amused and happier than those who didn’t smile.

So he came to the astonishing conclusion that we smile when we're happy.

In a more recent study, one group of participants received botox treatment for frown lines, which paralyzed the corrugator muscles in their brow.

The participants couldn’t express sad or distressed emotions in their face, and their reported positive mood was higher than other participants who received different cosmetic procedures.

Aside from genuine smiles and frown-muscle paralysis, there’s hope for our fake smiles too.

One study found that when participants were asked to fake a smile while completing a stressful activity,

they had lower heart rates during a stressful recovery period than those with the neutral expression.

So forcing yourself to smile can make you happier.

It goes to show that if you grin and bear it, it’s more likely your sadness and stress will help to hibernate your worries away.

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