A walk in the woods—or even a sound machine that plays recordings from nature—can affect heart rate and alter connections in the brain, say researchers.
By Updated February 22, 2021
You know that feeling of clear-headed calm that washes over you when you listen to water babbling down a stream, or leaves rustling in the wind? Researchers say they’ve pinpointed a scientific explanation for why sounds from nature have such a restorative effect on our psyche: According to a new study, they physically alter the connections in our brains, reducing our body’s natural fight-or-flight instinct.
Natural sounds and green environments have been linked with relaxation and well-being for hundreds of years, of course. But the new research, published in the journal Scientific Reports, is the first to use brain scans, heart-rate monitors, and behavioral experiments to suggest a physiological cause for these effects.
To investigate the connection between the brain, the body, and background noise, researchers at Brighton and Sussex Medical School in England recruited 17 healthy adults to receive functional magnetic resonance imaging (fMRI) scans while listening to a series of five-minute soundscapes of natural and manmade environments.
During each soundscape, participants also performed a task to measure their attention and reaction time. Their heart rates were monitored as well, to indicate changes in their autonomic nervous systems—the system of organs involved in involuntary processes such as breathing, blood pressure, temperature, metabolism, and digestion.
When they studied the fMRI results, the researchers noticed that activity in the brain’s default mode network—an area involved in mind wandering and “task-free” states of wakefulness—varied depending on the background sounds being played. Specifically, listening to artificial sounds was associated with patterns of inward-focused attention, while nature sounds prompted more external-focused attention.
Inward-focused attention can include worrying and rumination about things specific to one's self—patterns that have been linked to conditions involving psychological stress (including depression, anxiety, and post-traumatic stress disorder). Participants’ reaction times were slower when they listened to artificial sounds compared to natural ones, as well.
Slight differences in heart rate were also detected, indicating a shift in the body’s autonomic nervous system response. Overall, nature sounds were associated with a decrease in the body’s sympathetic response (which causes that “fight-or-flight” feeling) and an increase in parasympathetic response—the one that helps the body relax and function in normal circumstances, and is sometimes referred to as the “rest-digest” response.
Those results weren’t the same for everyone, though: People who started the study with the highest sympathetic responses (suggesting high levels of stress) registered the biggest relaxation benefits from the nature clips. People who started with low levels of sympathetic response, on the other hand, actually had a slight increase when listening to natural versus artificial sounds.
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Lead author Cassandra Gould van Praag, PhD, a research fellow at the University of Sussex, says the study’s findings may have real-world impacts—especially for people with high stress levels. “I would definitely recommend a walk in natural surroundings to anyone, whether they're currently feeling frazzled or not,” she told Health via email. “Even a few minutes of escape could be beneficial.”
Gould van Praag says the research has inspired her to get outdoors for breaks or listen to nature sounds using an app throughout her workday. “I really did find the downloaded tracks helpful for those times when I couldn't get away from my desk,” she says. (She adds that it took some time to find an app “that was right for me,” so she doesn’t recommend rushing into any software or noise-machine purchases without trying them first.)
Once you settle on a nature sound you find pleasant, Gould van Praag says it may also help improve your focus and concentration. In the study, participants performed best at "attention tasks" when listening to sounds that were considered familiar, compared with unfamiliar ones. “I think this supports the importance of finding an environment or sound machine that is right for the individual,” says Gould van Praag. “Rainforest noises might only have a strong relaxing effect if you are already very familiar with rainforests!”
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Finding that ideal background soundscape could potentially help to promote better rest, as well. “Poor sleep causes autonomic stress (the fight-or-flight response), and autonomic stress causes poor sleep,” she says. “This would suggest that anything which can reduce the fight-or-flight response may be beneficial to improved quality of sleep.” Minimizing manmade noise—like street traffic—may also be helpful, she adds.
(Sources: Health)
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