Parents, teachers and caregivers have long sworn by the magic of storytelling to calm and soothe kids. Researchers working in pediatric intensive care units have now quantified the physiological and emotional benefits of a well-told tale.

“We know that narrative has the power to transport us to another world,” says Guilherme Brockington, who studies emotions and learning at Brazil's Federal University of ABC in São Paulo and was lead author on the new paper, published in the Proceedings of the National Academy of Sciences USA. Earlier research suggested that stories help children process and regulate their emotions—but this was mostly conducted in a laboratory, with subjects answering questions while lying inside functional MRI machines. “There are few studies on physiological and psychological effects of storytelling” in a more commonplace hospital setting, Brockington says.

So investigators working in several Brazilian hospitals split a total of 81 patients ages four to 11 into two groups, matching them with storytellers who had a decade of hospital experience. In one group, the storyteller led each child in playing a riddle game. In the other, youngsters chose books and listened as the storyteller read them aloud. Before and after these sessions, the researchers took saliva samples from each child, then asked them to report their pain levels and conducted a free-association word quiz.

Children in both groups benefited measurably from the interactions; they showed lower levels of the stress-related hormone cortisol and higher levels of oxytocin, which is often described as a feel-good hormone and is associated with empathy. Yet kids in the storytelling group benefited significantly more: their cortisol levels were a quarter of those in the riddle group, and their oxytocin levels were nearly twice as high. Those who heard stories also reported pain levels dropping almost twice as much as those in the riddle group, and they used more positive words to describe their hospital stay.

The study demonstrates that playing games or simply interacting with someone can relax kids and improve their outlook—but that hearing stories has an especially dramatic effect. The researchers “really tried to control the social interaction component of the storyteller, which I think was key,” says Raymond Mar, a psychologist at York University in Canada who studies the effects of storytelling but was not involved in the new research.

Next, the investigators plan to study how long these effects last, along with storytelling's potential benefits to kids with particular illnesses such as cancer. For now Brockington says the results indicate storytelling is a low-cost and extremely efficient way to help improve health outcomes in a variety of settings. Mar agrees. “It's very promising and scalable,” he says, “and possibly generalizable.”