Adopting a smile can make you feel happier, large global study finds

Do your facial expressions affect how you feel? Does smiling make you happier? Does frowning make you sadder?

The idea that facial movements influence emotion (the 'facial feedback hypothesis') is contentious, to say the least. That's mostly because research in the field has produced some very mixed results. In 2016, one of the best-known findings in support of the idea — that simply holding a pencil between the teeth to simulate a smile made people feel more amused by humorous cartoons — notoriously failed to replicate. This replication attempt involved 17 independent teams, and was hailed by some as a nail in the coffin for the facial feedback hypothesis. However, a well-regarded 2019 meta-analysis of 137 studies concluded that facial feedback can have an effect on emotion — albeit small.

This uncertainty led a global group of researchers to come together to form the Many Smiles Collaboration. Some were for the hypothesis, some against it, and some had no strong feelings. Together, they developed what they believe to be the best tests of the theory. And they now report their findings on 3,878 participants in a total of 19 countries, in Nature Human Behaviour.

The team set out to answer these fundamental questions:

• Does adopting a happy expression make people happier than holding a neutral one?
• Do 'happy' facial poses only influence feelings of happiness if they are close to natural smiles (as opposed to the more unnatural facial muscle configuration caused by holding a pen between the teeth)?
• Can a smile pose actually initiate feelings of happiness in a neutral scenario?
• If there are facial feedback effects on emotion, do they occur only among people who are aware of the hypothesis?

The participants were given a cover story (that the study was designed to investigate how physical movements influence maths performance), and a set of tasks. During a few of these tasks, they adopted happy or neutral facial expressions. But different groups got different instructions. Some participants were told to copy the happy or neutral expression of an actor in a photo; some were given guidance on what to do with their facial muscles (to mimic a smile or neutral pose); others had to hold a pen either in their teeth (happy condition) or between their lips (neutral). Each pose was held for five seconds. While doing this, half of the participants were also shown some positive images (such as pictures of flowers, rainbows and kittens).

After each task, the participants completed a brief questionnaire that asked about their levels of happiness, 'liking' and enjoyment during that task (to maintain the ruse, they also completed maths problems). After completing all of the tasks, they answered questions about their beliefs about the purpose of the experiment. They also completed a body awareness questionnaire, which asked them to rate their sensitivity to everyday physical changes in their body.

The researchers' extensive analyses of the data produced these main results:

• Facial feedback did influence feelings of happiness. But a 'smile' was clearly associated with greater happiness only when it was either copied (from the actor's face) or created by voluntary movement of the facial muscles. When the 'smile' was created by holding a pen between the teeth, there was only "equivocal" evidence of an effect on happiness.
• These effects on happiness occurred whether or not the participants also saw positive images, suggesting that a smile expression can itself initiate feelings of happiness, rather than just amplify underlying feelings of happiness.
• Participants who had no idea about the facial feedback hypothesis still experienced these effects — though the effects were weaker.
• Body awareness scores had no bearing on the results.

The impacts on happiness ratings, when they were observed, were small. But these results are important for a few reasons.

The first is theoretical. They support the idea that physical changes in our bodies can at least influence our emotional experiences. Why didn't holding a pen between the teeth affect happiness? Perhaps because this pose didn't recruit as many of the natural smile muscles as in the other smile conditions — and people need to infer that they are actually smiling for an effect on feelings of happiness. Whatever the reason, as the team writes, with this new "strong evidence" of facial feedback effects, future research can now explore exactly when and why they occur.

The second reason is practical. It has been suggested that simply smiling in the mirror for five seconds each morning may reduce distress, improve wellbeing and alleviate depression. This new work supports that idea that this may indeed happen, though many of the researchers doubt that the impact will be substantial. However, given the new results, "it is possible that relatively small facial feedback effects could accumulate into meaningful changes in wellbeing over time."

One last note: whether smiles really are an expression of happiness is debated. There is a theory that our facial 'expressions' are better understood as tools for social influence. In this view, a smile signals a willingness to engage in a positive social interaction, rather than 'happiness'.If this is the case, then facial muscle movements wouldn't be expected to have a sizeable impact on emotions — and the effect sizes in this study were of course small.

Whether or not this is a reason for the small scale of the effects, the limited impacts on happiness found in this study shouldn't be taken to indicate that perceptions of physical changes are not very important for our emotional experiences. Other bodily signals — for example, the sensing of a racing heart during a dispute — may have a far greater impact on emotion.