Keeping a genuine smile on your face while you’re under stress can be good for your heart, new research shows. Investigators at the University of Kansas set out to test whether the old adage “grin and bear it” can give you an edge when you’re stressed. They taught 169 volunteers how to hold neutral expressions on their faces, as well as how to hold standard smiles or “Duchenne” smiles (here, you consciously use the muscles around your mouth and the eyes to shape the smile). The volunteers were even taught how to maintain a forced smile by propping their mouths with chopsticks. After this training, the researchers put the volunteers through a series of stressful activities such as plunging their hands in buckets of ice water or using their non-dominant hands to follow the path of a moving star seen in a mirror. They didn’t tell the volunteers that these actions were aimed at generating stress, but the researchers did monitor the volunteers’ heart rates during the tests. They found that those who had been told to keep Duchenne smiles on their faces had lower heart rates after the stressful activities than those with neutral expressions. Even those whose smiles were forced by holding chopsticks in their mouths had lower recovery heart rates compared to those instructed to maintain neutral expressions. The study was to be published in a forthcoming issue of Psychological Science.