It won’t bring sunshine to the darkest days, but those in need of a little cheer may want to extend the corners of their lips towards their ears and lift their cheeks towards their eyes – using only their facial muscles, mind. After decades of argument and counter-argument, psychologists have apparently agreed that arranging one’s features into the shape of a smile helps brighten the mood. In other words, if you want to feel a little happier, try looking a little happier first. Researchers have long wondered whether the physical manifestations of emotions, from smiling and laughing to crying and a pounding heart, ramp up the intensity with which an emotion is felt. According to the “facial feedback hypothesis”, smiling should make people feel happier, while frowning should make them sadder. The idea has a rocky history, though. According to an influential study in the 1980s, people found Gary Larson’s The Far Side comics funnier when they held a pen between their teeth without letting their lips touch it. Holding the pen thus was said to activate smile muscles, sending positive signals to the brain. But the idea took a hit in 2016 when 17 different laboratories failed to replicate the pen-in-mouth study. Three years later, a meta-analysis of more than 100 published studies found there probably was an effect after all, but the debate continued to rage. To settle the matter once and for all, Nicholas Coles, a research scientist at Stanford University, organised the Many Smiles Collaboration to conduct an experiment that advocates, critics and those on the fence could all endorse. The psychologists recruited nearly 4,000 people from 19 countries and divided them into three groups. The first adopted the pen-in-mouth method to activate facial muscles for smiling. The second mimicked the facial expressions of smiling actors. The third was told to move the corners of their lips towards their ears and raise their cheeks, using only the muscles in their face. The volunteers then rated their happiness as they pulled the faces, wore neutral expressions, and looked at a blank screens or images of puppies, kittens, flowers and fireworks. According to a report in Nature Human Behaviour, the pen-in-mouth method did little for emotions – perhaps because people had to grit their teeth. But the other two approaches boosted happiness, though the effect was small – equivalent to looking at happy photos. “Some people believe that emotional experience is very cognitive – that’s it’s solely driven by our evaluations of what’s going on in the world. This work, however, suggests that it’s also physiological,” said Coles. “Emotional experience appears to be built, in part, off of feedback or sensations from the peripheral nervous system. The accelerated heart can make people feel anxious, the furrowed brow can make them feel angry, and the stretch of a smile can make them feel happy.” Dr Magdalena Rychlowska, who works on facial expressions, emotions and culture at Queen’s University, Belfast, said such studies were “tremendously beneficial” for psychology. “As a researcher working on how facial movements influence our feelings, I am delighted to see that an independent, rigorous, and inclusive study found support for the facial feedback hypothesis,” she said. Tony Manstead, emeritus professor of psychology at Cardiff University, praised the group for doing a “fine job” but remained cautious about the results. The effect was greatest in volunteers who knew about the facial feedback hypothesis and who rated their posed expressions as genuine, he said. While the psychologists found a significant effect in people who were unaware of the feedback hypothesis, Manstead said volunteers seemed to infer how happy they were, at least in part, from cues that included facial expression. “Having your attention drawn to your face by asking you to pose an expression probably increases the salience of these cues,” he said.