Lake Serene sits just south of Mount Index in the Central Cascades range, glistening high above Gold Bar at an elevation of about 2,500 feet. You can access it by hiking a steadily inclining trail through old growth evergreens, abundant fern beds and mossy undergrowth. A serene state of mind is harder to geolocate, but according to recent brain science, a walk in the woods will get you there, too.
On this particular morning, I haven’t arrived at either yet. After a few false starts (including the car not starting), my husband Daniel and I pull away from the house at the crack of 10:45 a.m.Heading north on Interstate 5 toward Stevens Pass, my brain travels well-tread loops of agitation. Why didn’t we get up earlier? Why didn’t we buy the trail snacks last night? Why is it so hard for us to spontaneously hit the road? We really should’ve started earlier. And so on.
Having previously interviewed an expert on this style of fretting, I know the psychological term for it: rumination (from the Latin, “to chew over again”). Unlike introspection, which can be productive, rumination involves repetition of negative thoughts and fixation on problems rather than solutions. Greg Bratman, assistant professor of Nature, Health and Recreation at the University of Washington’s School of Environmental and Forest Sciences, studies nature as a potential salve for this sort of self-criticism, which can range from standard worrying to full-on depression and mental illness.
“Lots of your working memory gets used up with rumination,” Bratman told me over the phone. “So if you ruminate less, you could perform better in other cognitive tasks.” His specific area of research is mental health. “I’m focused on the emotional effect of a nature walk—the possibility that it could increase our cognitive ability to get a grip on our emotional state.”
Ruminative thoughts—which have a higher incidence in urban dwellers—are associated with an area of the brain called the subgenual prefrontal cortex (sgPFC). In a 2015 study, Bratman scanned for activity in this region before and after sending two sets of participants (all of whom lived in an urban environment and had no history of mental disorder) on 90-minute, solo, cellphone-free walks. One group walked alongside a busy thoroughfare; the other walked a path through a natural green space.
For anyone who enjoys a leafy walk, these results aren’t terribly shocking.
His team found that participants who went on the urban walk had no change in ruminative brain activity (scanned or self-reported), but those who took the nature walk saw a reduction in self-reported rumination and significantly less activity in the sgPFC—as if it simmered down. In short: Those who walked in nature felt more clear-headed. For anyone who enjoys a leafy walk, these results aren’t terribly shocking.
“People always say, ‘So you study something I already know,’” Bratman told me, well aware that his chosen field of study is viewed as common knowledge. “We know being in nature makes us feel better. But we’re trying to figure out exactly why and how.”
Back on I-5, I ponder the healing potential of nature while crawling through the IES (Inevitable Everett Slowdown). The abstract forest and mountain designs adorning the freeway’s massive retaining walls aren’t doing the trick. But just as we exit onto U.S. Highway 2, I see an eagle, with a seagull in hot pursuit, flying east toward Ebey Slough. I get it, birds, I think. Turn here for nature!
As we wend along, Mount Rainier’s bald white head peeks out behind closer mountain ranges. The Skykomish River snakes beside us. I see forests and farmlands—so many shades of green. I feel a sort of mental unclenching.
We know being in nature makes us feel better. But we're trying to figure out exactly why and how.
Just after Gold Bar, we turn right onto Mount Index Road, find the Lake Serene trailhead parking lot and get the last open spot. It’s just after noon. We should’ve left earlier. We throw on backpacks and hiking shoes and set out. The trail is instantly lovely, shaded by alders, maples and salmonberry bushes. At this hour, there aren’t many people heading out in our direction, so it’s quiet—just the tromping of our shoes hitting packed earth. The air smells of pine and dirt. “We’re forest bathing,” I inform Daniel, eager to share some recently learned terminology.
A Japanese tradition since the 1980s, forest bathing (or shinrin-yoku) has been recently getting a lot of press in the U.S.—last summer the Washington Post deemed it the “latest fitness trend.” But it’s not about exercise (and despite the name, not about nudity either). The idea is to immerse yourself in the woods and take it all in—sights, smells, sounds and tactile experiences. Japanese studies have shown that doing so decreases blood pressure, heart rate and stress hormones, and increases a sense of wellbeing.
I check in on my own wellbeing. It’s hard to sneak up on your brain and see what it’s doing, but I don’t think I’m thinking much at all. In a short time, I’ve already begun to experience that floaty feeling I get while hiking, when my mental hyperactivity melts away and is replaced by something more bodily. The “thoughts” I’m having are akin to foot forward, foot forward, ooh pretty moss, twisted tree, sun dappling, foot forward, foot forward. I decide to try and ruminate a bit. What about those emails I’ve been meaning to send for days? That seems like something I could really fixate on. But each time I try, my mind goes adrift. Left foot, right foot, puffy cloud, nurse log.
Later, I’ll relate this self-devised scientific study to another expert on the human brain in nature, Marc Berman, director of the Environmental Neuroscience Lab at the University of Chicago. “That’s because your involuntary attention was engaged,” he explains. Berman’s work is centered on the Attention Restoration Theory, which asserts that humans have two states of attention, directed and involuntary. We need the former to complete difficult tasks, push away distractions and get work done. The latter is engaged effortlessly by interesting, but less demanding stimuli—such as a natural green space. He calls the state of involuntary attention “soft fascination” (which sounds to me like an ’80s synth band).
Berman’s research shows that when involuntary attention is engaged, it gives directed attention the chance to rest and recuperate. In one study, he found that after a 50-minute walk in nature, participants performed 20 percent better on cognitive tests (such as repeating long strings of numbers backward), as compared to people who walked in busy urban areas. He adds that while directed attention gets fatigued fairly quickly (leading to irritability, impatience, a decrease in altruistic behaviors and other unpleasantness), involuntary attention seems almost bottomless. “Lots of people feel mentally spent after a long day of work,” Berman says, “but nobody ever says, ‘I’m really exhausted from looking at this waterfall.’”
Speaking of waterfalls. Back on the trail, Daniel and I take the steep spur up to Bridal Veil Falls, booming with water and kicking up quite a spray. “Well, this is a mist opportunity,” I say. “Should we keep moving?” Daniel asks. “Moss definitely,” I reply. I note that the part of my brain responsible for puns is experiencing a high rate of activity. After making a particularly arduous climb that tops out at a beautiful overlook, I say, “I guess what’s good for the glutes is good for the gander!” In the moment, I both recognize the silliness of these jokes and feel invigorated by them.
What is it about nature that soothes and softly fascinates the brain—that blocks pessimistic thoughts and replaces negative with positive emotion? Bratman and Berman both concede that given the multiple factors at play, it’s hard to isolate the cause/effect. But in recent studies, Berman has shown that our involuntary attention is drawn to curved edges (as opposed to the straight lines of built environments)—especially fractal patterns, those branching repetitions seen in leaves, ferns, trees, river deltas and mountain ranges. He’s also found that when the brain is at rest, over time it enters a more fractal state (with repeated brain patterns) than when the brain is working hard. Coincidence?
Lots of people feel mentally spent after a long day of work,” Berman says, “but nobody ever says, ‘I’m really exhausted from looking at this waterfall.’
Many questions remain. There’s dosage—how much nature is needed to be curative? And how long do the effects last? What types of nature work best? Researchers have been able to quantify that bigger trees have a larger effect than smaller ones, and evergreen trees have more restorative punch than deciduous. But does it matter whether they’re in a manicured Japanese garden or a wild forest? How big a role does sound play? Smell?
The overarching goal for both Bratman and Berman is access. As Bratman posits in the conclusion of his study, “Feasible investments in access to natural environments could yield important benefits for the ‘mental capital’ of cities and nations.” As our world becomes more urbanized, more covered in concrete and straight lines, how might these findings be used in city planning? If people can’t get to the trees, can we bring the trees to them?
Out in nature, Daniel and I make our final, scrambly push and round the corner to Lake Serene. It’s stunning—a perfect pool of green water, the dark rocky face of Mount Index shooting up like a castle keep. The place is teeming with fractals. Leftover slumps of bright snow are melting fast, adding a soft rushing sound underneath the birdsong. We see a sign for Lunch Rock and take its advice. We sit there for a long while, staring at the water, the trees, the mountain, serene and softly fascinated. We arrived at the perfect time.