Though I’ve yet to explore all of Duke’s nooks and crannies, I feel confident that my favorite corner of campus will always be the Sarah P. Duke Gardens. Nature, and green space generally, is good for us as humans. Most of us understand this on an intuitive level, but what’s the underlying reason? How might it be built into our brains?
Psychology professor Marc G. Berman looks for the answers. At the University of Chicago, Berman directs the Environmental Neuroscience Lab, in which he investigates interactions between our brains and our physical surroundings. In a recent virtual Grand Rounds lecture in Duke’s Department of Psychiatry & Behavioral Sciences, Berman spoke about the broad scope of his research and its implications for a better society.
Attention Restoration Theory
Researchers have proposed various theories for why we love nature. For example, the biophilia hypothesis states that humans have an innate attraction to nature on a genetic and evolutionary basis. However, Berman is focused primarily on the Attention Restoration Theory, a concept he’s contributed to significantly. Under this theory, attention is split into two types: directed and involuntary.
The first type is finite––think about the amount of energy it takes you to deliberately concentrate on something. “The first five minutes of lecture, everybody’s very focused on me,” Berman said, using the example of his own classes. Forty-five minutes later, and people inevitably begin to nod off.
On the other hand, involuntary attention is not really under our control and isn’t as susceptible to becoming drained. Within stimuli that capture our involuntary attention, some are softer or harsher than others, like a stream compared to flashing lights (the stream being a softer attention capture, which we call soft fascination).
The cornerstone of Attention Restoration Theory is that nature provides an ideal environment for the restoration of directed attention; full of “softly fascinating” features, it stimulates involuntary attention without placing demands on directed attention.
A Walk in the Park
Roughly 20 years ago while Berman was a researcher at the University of Michigan, he and his colleagues wanted to test out the Attention Restoration Theory. So, after asking study participants to perform a backwards digit span task (a test for memory that would require directed attention), they told them to take a walk. Participants were directed to either a route through downtown Ann Arbor, or through the Nichols Arboretum. Then another digit span test. A week later, they repeated the whole procedure, this time walking in the other environment. Interestingly, walking through the arboretum proved more beneficial for memory. “We see about a 20% improvement in this task after people go on this brief 50-minute walk in nature versus walking in the urban environment. So that’s pretty impressive,” Berman said.
Many of us wouldn’t be surprised by this–certainly, I know a walk in the Gardens on a pleasant day recharges my ability to focus. Time in green space and warm weather often lifts our moods, but they discovered that this cognitive benefit occurs regardless of how you feel afterwards. Walkers turned cranky from the winter cold demonstrated improvements on par with those who gladly embraced sunny weather in June.
Berman saw even more of a positive effect for the park-goers when repeating the study with participants diagnosed with depression, contrary to a concern that walks alone might induce rumination on negative thoughts.
Cities: Better Than You Think They Are
In the Environmental Neuroscience Lab, Berman and doctoral students look at everything from brief interactions with nature to the long-term effects of living in large cities. Given everything thus far, it would seem logical that the latter would be far worse for our brains than other environments. Yet, Berman found just the opposite.
As it turns out, cities are beneficial for our social connectivity. Since people tend to encounter each other more often in urban areas, an individual will likely develop more social connections on average. Prior neuroscience studies have connected a greater number of social relationships to protection against depression.
Based on this, the risk of depression might be aptly represented by an inverse model of the number of people in one’s social network. In other words, the more people you maintain contact with, the lower your risk. To test it, Berman and collaborators enlisted four different data sets regarding depression–including in-person interviews, phone interviews with personal demographics, and over 15 million tweets (converted via machine learning algorithms into a PH-Q depression inventory score). The results confirmed it. “What we see across all of these different data sets is that as cities get larger, you get less depression per capita,” he said.
“Many of us have this impression that in bigger cities like New York, like Chicago, like Los Angeles, people are not as friendly…but these results suggest the opposite,” Berman said. “It must be on average that those social interactions are positive in cities and that more is better.”
Designing Environments for Our Brains
Regarding the main conversation surrounding mental health, Berman said, “We often think about [depression] in terms of this individual scale…your genetic makeup, brain activity patterns, individual psychological patterns. Maybe things about your family. We don’t really think about your neighborhood and your city.”
Knowing what we do about nature and large social networks can ultimately help us improve mental health outcomes on a broad scale. These two factors might seem to work against each other, but they don’t have to. Ultimately, we need more green space everywhere, including in large cities. The benefits are undeniable–urban areas with more greenery consistently see less aggression and crime, even when adjusting for race, ethnicity and income.
In addition, cities tend to have a lot of harsh stimuli, but that doesn’t mean some features of urban environments can’t be potentially restorative. “We believe that certain environmental features can be designed to improve human performance and well-being, like incorporating more natural features or natural patterns in the environment, trying to figure out ways to increase social interactions,” Berman said. By mimicking aspects of nature like curved lines, we might be able to create “soft fascination” closer to home and reduce the different demands pulling on our attention.
Crystal Han, Class of 2028
Guest post by Amy Lei, North Carolina School of Science and Math, Class of 2025.