Sometime during my third year of college, my roommate started suggesting we take walks from our apartment on Harper Avenue to Promontory Point. “I’m going for a walk to the Point,” he’d say offhandedly, as though the idea had only just occurred to him. “Do you want to come along?”

It took me a few weeks to put together that he always suggested these little strolls just as I was about to approach peak academic overwhelm (an almost daily occurrence after about the fifth week of the quarter). I realized, with some amount of indignation, that I was being walked like a dog.

The trouble was, it worked. We’d arrive at the Point, and as I took in the subtly changing colors of the trees and the lake, whatever crisis was brewing in my mind—I have nothing original to say about Walden, or I’m pretty sure I definitely don’t understand Foucault—suddenly felt manageable.

It was hard to be annoyed. I kept taking my troubles to the lake, and the lake kept solving them.

The idea that spending time in nature benefits us mentally feels axiomatic. But proving it scientifically is surprisingly difficult—and understanding why we feel better after a ramble in the outdoors is even more bedeviling. There’s a turtles-all-the-way-down quality to the topic: How can we quantify the effects of our environment? What does it mean to feel better anyway? For that matter, what do we mean by nature? Is it flowers? Trees? Actively erupting volcanoes?

Professor of psychology Marc Berman has been working intently to answer these questions ever since he was a University of Michigan graduate student. In the process, he has emerged as one of the leaders of a new interdisciplinary field, environmental neuroscience, that investigates the relationship between the human brain and its surroundings. Berman’s recent book Nature and the Mind: The Science of How Nature Improves Cognitive, Physical, and Social Well-Being (Simon Element, 2025) lays out what his and others’ work has uncovered about the link between the exterior world and our interior experiences.

Berman, who leads the Environmental Neuroscience Lab at UChicago, came to both his current field and his research topic sideways. His undergraduate degree is in engineering; that training, he believes, informs his approach to psychology. “Engineers think in terms of systems,” he says. “A lot of psychologists and neuroscientists were thinking about brains as a system, but not brains and the environment as a system.”

In 2006, as a graduate student, Berman conducted a study that helped lay the foundation for environmental neuroscience. He often calls it the “walk-in-the-park study,” but its full title, as published in the journal Psychological Science in 2008, is “The Cognitive Benefits of Interacting with Nature.” It includes multiple experiments that tell a single compelling story.

In the first experiment, study participants were asked to report their moods, then given a tricky task designed to tax their attention. They heard a sequence of digits one at a time (say, 0-9-8), which they had to repeat backward (8-9-0). The sequences got longer and longer, up to nine digits. The backward digit-span test, as it’s called, has been used to test working memory—the ability to temporarily retain information for active use, like remembering a phone number you’re about to dial.

After finishing this brain-scrambling feat, participants took a 2.8-mile walk through either downtown Ann Arbor, Michigan, or the Ann Arbor Arboretum. When they got back to the lab, participants once again reported their moods and repeated the backward digit-span test. A week later participants did it all over again, with one important adjustment: Those who’d previously taken the downtown walk took the park walk and vice versa.

In his book Berman describes the thunderclap moment when he started analyzing the results of this experiment. Taking a walk in nature improved performance on the backward digit-span test by about 20 percent—the kind of startling statistical improvement that will make an experimental psychologist take notice. “I practically screamed when I saw it on my computer screen,” Berman writes in Nature and the Mind.

The walk-in-the-park study changed Berman’s life and career, attracting scholarly discussion—it is still, almost 20 years later, his most cited publication—as well as media attention and funding for his research.(Like a band forever defined by a hit single, Berman has also occasionally felt pigeonholed: “People sometimes think, ‘Well, Marc’s the nature guy,’ and that can be constraining,” he says. “I mean, I do other work showing that cities are good.”)

Everybody seemed to have an opinion about the research, which attracted some “what about”-ish responses. How, people wanted to know, could Berman be sure this was about nature, not about walking or the pleasures of a summer day? Would the results hold true even for the most stubbornly indoorsy?

Berman points out that the experiment was repeated in good and bad weather alike (warm days in June and cold days in January), and that people’s attitude toward nature had no bearing on the cognitive benefits they received from taking a walk in it. People who dislike the outdoors are still sharpened by it. (Liking nature and walks was necessary to improve people’s moods after the walk—but not their performance on the backward digit-span task.) And it’s not only the magic of getting your steps in. A second experiment tested the effects of looking at photos of natural versus urban environments and found that only images of nature improved performance on the digit-span test—not as strongly as the real thing, but still an improvement.

“This isn’t just about liking or pleasantness. It’s not like laughing at a joke and feeling good,” Berman says. “Something deeper is happening.”

So what, exactly, is that deeper thing, the mechanism giving rise to the cognitive benefits of nature? Some scholars believe that interacting with nature, as compared to urban environments, reduces stress, with positive physiological and cognitive effects. Others point to the biophilia hypothesis, which proposes that humans have an innate, perhaps genetic, tendency to seek connections with nature. Some see a social explanation—perhaps being in nature helps us feel more connected to the world and each other.

Berman favors a theory—first proposed by University of Michigan professors Stephen and Rachel Kaplan—that suggests attention is the key. According to this model, called attention restoration theory, humans have two basic types of attention. Involuntary attention is uncontrollable and almost reflexive—it’s why we notice the snap of a twig on a quiet night in the woods, whether we’re listening for it or not. Directed attention, by contrast, is what we choose to focus on in an intentional and deliberate way.

Directed attention is a limited resource, as Berman knows well. “When I’m lecturing, for the first five minutes of class, all eyes are on me,” he says. “Forty-five minutes into the class, students are doing all kinds of stuff. It’s hard to direct attention.”

Attention restoration theory posits that the cognitive benefits of spending time in nature spring from the renewal of directed attention. Like an aquifer recharged after a heavy rainfall, he and others believe, our directed attention can be replenished by time in the great outdoors.

The original walk-in-the-park study provided important evidence for this theory. In addition to the backward digit-span test, Berman also had participants complete the Attention Network Test (ANT), which measures response time to visual stimuli and allows researchers to measure different types of attention. In the study, viewing photos of nature yielded improvements on the portions of the ANT associated with directed, rather than involuntary, attention; no such improvements came about after participants viewed photos of urban environments.

Berman continued to investigate the attentional benefits of time in nature. In one paper, published in 2012, he repeated the walk-in-the-park study with a group of participants suffering from depression. Depression is a condition characterized, in part, by overburdened attention—the people in its grasp cannot stop rehearsing failures, bad memories, and negative experiences. “Depressive rumination makes it hard to focus on anything else,” Berman writes in his book, “because our [directed] attention has been spent.”

For participants with depression, a walk in nature had even greater cognitive benefits than Berman observed in his original research; that is, performance on the backward digit-span test improved even more drastically. As in the original study, walks in nature also improved participants’ moods more than walks in urban environments did. Interestingly, the two benefits didn’t appear to be related—statistical analysis suggested that people didn’t get better at the backward digit-span test just because their mood improved.

It was a hopeful study for many reasons. Perhaps, Berman and his collaborators theorized, the more your attention is overtaxed, the more nature can help.

The turtle below this turtle is, of course, the question of why nature restores attention in a way that urban environments do not. This, too, is open to debate.

Berman and others have proposed that for an environment to renew attention, it must have a kind of Goldilocks quality: interesting enough to engage you, but not so interesting it overtakes you. The Kaplans call this harmonious quality soft fascination, and Berman believes nature is rich with it.

“If I see a beautiful waterfall, it captures my involuntary attention, but I can still think about other things, I can kind of mind wander,” Berman says. Walking through Times Square, too, captures involuntary attention, “but it sort of does so in a very harsh and all-consuming way. I can’t really mind wander or think about other things.”

The concept of soft fascination, Berman admits, can seem “kind of squishy.” But his continued research is helping to hone and sharpen our understanding of it. Softly fascinating environments, he has found, are characterized by a balance between complexity and predictability. The visual patterns of nature have this same balance—think of tree branches, which break off into yet more branches in an intricate, fractal-like pattern that we can perceive at close range or from a distance.

He’s also found some early evidence that, perhaps because of these repetitive qualities, images of nature may be easier for our brains to process. Berman and his PhD student Nakwon Rim, AM’21, have discovered that images of nature are easier for computers to compress algorithmically than photos of urban environments. That is, computers can alter photos to take up fewer bytes of memory without altering how they appear to the human eye, and this compression is stronger for natural scenes than human-made or urban scenes. Our brains may be doing a version of this same compression, taking in a natural scene but affording it less mental space than an urban scene.

Whatever the cause, the cognitive and affective benefits of time in nature are consistent, striking, and (insect bites and sunburns notwithstanding) free of major side effects.

In Berman’s view, that warrants a major mindset and policy shift. Nature “is not an amenity—it’s a necessity,” he says. “We can’t be our best without nature.”

Of course this doesn’t mean everyone has to move to the countryside. (Berman himself divides his time between two major cities, Chicago and Toronto.) Rather it means that policymakers in urban areas should no longer regard green spaces as a nice-to-have, a tiny line item in the budget that can be relegated in lean times. Green space is “a human need,” Berman says, and something “you have to preserve a substantial amount of, no matter how big the city gets.”

While these big policy questions are adjudicated, Berman is not above small life hacks. “Fake plants and artwork that mimic patterns in nature can be beneficial,” he says. In Nature and the Mind he suggests that even watching videos of nature or listening to nature sounds can improve attention, especially as compared to the mindless scrolling many of us think of as a break.

I am one of the many. Quite often, after I finish an interview, I find myself trying to “wind down” with help from a high-velocity stream of pictures and videos on the internet. I know perfectly well this is counterproductive, like asking someone to yell “YOU SHOULD RELAX” directly in my face while a smoke detector goes off. After I talked to Berman, though, I took a moment to look at the tree outside my front window, explaining to my bemused husband that I was “looking at fractals.”

Afterward, I had to admit, I did feel a little bit better.