We all love to listen to those nature recordings made to help you sleep because they contain chill and comforting environments like summer rain storms, jungle noises at night, and ocean waves crashing on the shore—they naturally make you more calm and take you out of your head. But no one really knew why they did that; so, to find out, the scientists at the Brighton and Sussex Medical School in the U.K. recently put together a study that examined people who listened to natural sounds while in a functional MRI machine.

Researchers monitored the subjects’ brain activity through the MRI and their autonomic nervous system by measuring tiny changes in heart rate. They discovered that when listening to natural sounds, the default mode of the brain switched to an outward-directed focus of attention, and when artificial sounds were played the brain went into a more inward focus, which is similar to what happens in the brain when someone has anxiety, post-traumatic stress disorder, and depression. They found the natural sounds also increased nervous system activity connected to relaxation, and participants had better performance when given a task that concentrated on external attention.         

The greatest relaxation effect was also seen in those people who came into the study already highly stressed, said the authors. Curiously, those subjects who started with relaxed brains showed a slight increase in stress when the natural sounds were turned on compared to a listening session with artificial noises.

“We are all familiar with the feeling of relaxation and 'switching-off' that comes from a walk in the countryside, and now we have evidence from the brain and the body, which helps us understand this effect,” said lead author Cassandra Gould van Praag, Ph.D. “This has produced results, which may have a real-world impact, particularly for people who are experiencing high levels of stress.”