The emerging field of environmental neuroscience explores why and how our brains are positively impacted by spending time outdoors.
Research has already shown that green (vegetated) and blue (water) environments are associated with improved mood and a reduction in stress and anxiety. There is, however, new evidence emerging that suggests that exposure to nature also benefits cognitive function including memory, perception, judgement, problem-solving, and imagination.
Dr Marc Berman, director of the Environmental Neuroscience Laboratory at the University of Chicago, tasked subjects with a test known as the backwards digit-span task which required them to repeat back sequences of numbers in reverse order.
After the initial test, he split up the group and sent them for a 50-minute walk. One group was sent to an urban setting (a town centre) or an outdoor setting (a park). On their return, they repeated the task. “Performance improved by about 20% when participants had walked in nature, but not when they had walked in an urban environment,” he says.
Another study found that a four-day hike (with no access to phones or other technology) increased participants’ creativity by 50%. Additionally, according to the biophilia hypothesis, humans function better in natural environments because our brains and bodies evolved in, and with, nature.
“Biophilia makes a lot of sense,” says Dr David Strayer, a cognitive neuroscientist who heads the Applied Cognition Laboratory at the University of Utah. “As hunter-gatherers, those who were most attuned to the natural environment were the most likely to survive. But then we built all this infrastructure. We are trying to use the hunter-gatherer brain to live in the highly stressful and demanding modern world.”
Exposure to nature activates the parasympathetic nervous system or the branch of the nervous system related to a “resting” state. This elicits feelings of calmness that enable us to think more clearly and positively.
A recent theory proposes that oxytocin (the “bonding” hormone) may be behind the phenomenon, exerting its powerful antistress and restorative effects when we are in natural settings that we perceive as safe, pleasing, calm and familiar.
Neuroimaging tools such as electroencephalograms and functional magnetic resonance imaging are helping researchers observe the changes in our brains in real time. Functional magnetic resonance imaging (fMRI), for example, uses something known as Bold (blood-oxygen-level-dependent imaging) to determine which areas of the brain are most active during exposure to different stimuli.
Studies have shown a drop in the Bold signal in the prefrontal cortex (an important brain structure in executive function) during nature exposure. It has also displayed that a greater number of brain areas are activated when viewing urban scenes, which suggests more effort is required to process them.
There is also research that may link “higher-quality” environments with more biological benefits. This means places with more biodiversity such as an abundance of bird and tree species may yield less anxiety and better mood than less species-rich outdoor areas.
“This growing body of research is demonstrating that we can’t be healthy – that our brains do not work optimally – if we don’t spend time in natural environments,” says Berman. “It’s not a luxury – it’s a necessity.”