How Nature & Other Physical Environments Impact Your Focus, Cognition & Health | Dr. Marc Berman

This protocol is directly based on Berman's 2008 study (and subsequent replications). Participants performed a backwards digit span task, walked 2.6 miles (~50 min) in an arboretum without phones, then repeated the task, revealing a ~20% improvement in working memory. The effect occurred regardless of season and was not mediated by mood. The urban walk, in contrast, involved street crossings, traffic, and advertising that required vigilance and directed attention, preventing restoration. The mechanism is grounded in Attention Restoration Theory (Kaplan): directed attention is a finite resource that fatigues with use; environments that offer 'soft fascination'—moderately interesting but not demanding—allow that resource to replenish. Nature's fractal geometry, soundscape, and lack of semantic demands make it the prototypical restorative environment. Berman emphasizes that the walk should not be a meditation session; it is a passive, mind-wandering state. Shorter interventions (10 min of nature pictures or sounds) also work but are less potent.

Berman's lab tested a 10-minute picture-slideshow protocol: participants watched nature vs. urban scenes on a computer screen, then repeated the backwards digit span task. Those viewing nature showed improvement. A similar study with nature sounds through headphones also boosted working memory. These experiments control for the physical activity and novelty of being outdoors, isolating the sensory properties of nature. However, Berman cautions that the benefits are not as large as the 50-minute walk. He recommends looking out a window at nature, or even having indoor plants/fake plants, as additional tools. This protocol is especially useful for people in dense cities or during bad weather.

Berman collaborated with an architect to study building facades. People grouped buildings with fractal-like features together and preferred them. In another study, parks with more curved edges prompted journal entries about spirituality, and this effect was replicated in the lab with scrambled images—proving that curvature alone, not object identity, triggers spiritual cognition. Berman advocates for a 'nature revolution' in architecture: designing schools, hospitals, and offices to maximize fractal patterns and curved forms, not just for aesthetics but for cognitive and emotional health. This aligns with biophilic design, which seeks to connect building occupants to nature.

In a within-subject design, participants completed a demanding working memory task before and after a 50-minute walk either through the Ann Arbor Arboretum (nature) or busy Washington Street (urban). Walks were matched for length and participants were monitored via GPS; phones were collected. After the nature walk, backwards digit span performance improved by about 20% compared with the urban walk. Crucially, the same improvement occurred for participants who walked in freezing January weather and reported disliking the walk, while the summer walkers enjoyed it. Mood improvements did not correlate with cognitive gains. This dissociation indicates that something about processing natural sensory stimulation—not merely pleasure—restores directed attention. The study also ruled out that the urban walk was simply more dangerous, because crossing streets and traffic demanded vigilance, keeping directed attention engaged. The arboretum environment allowed involuntary attention to softly engage, recharging the directed attention system.

A student in Berman's lab (named Nwan) ran a JPEG compression algorithm on thousands of nature and urban images. Because JPEG compression is lossy—it discards some pixel information—it can achieve smaller file sizes when images contain repeated patterns. Nature images compressed to significantly fewer bits than urban images, meaning they have more redundancy (fractal structure, repeated textures). The human eye cannot easily distinguish the compressed nature image from the original, whereas urban images require preserving more unique pixels. This parallels how the brain might process visual input: natural scenes allow more information to be 'thrown away' or summarized, freeing cognitive resources. Berman also speculates that nature scenes are semantically simpler—there are fewer distinct objects to label (lake, tree, shrub) compared with the richer vocabulary needed for urban scenes (Volkswagen Beetle, Gothic architecture). Memory tests show people remember nature scenes less well than urban scenes, consistent with easier, less taxing processing.

Berman's team analyzed journals placed in small parks by the TKF Foundation (now Nature Sacred). Using topic modeling, they found that entries contained themes of religion, nature, and spirituality. Computer vision algorithms quantified the proportion of curved vs. straight edges in each park. Parks rated as more natural and with more curved edges were associated with more journal entries about spirituality and life journey. To establish causality, they ran an online study where participants viewed images (natural and urban) with varied edge curvature and then rated their associations. Images with more curved edges were more likely to be linked to spirituality. Critically, they then scrambled the images so objects were unrecognizable, and still the scrambled images with more curved edges elicited stronger spirituality associations. This shows the effect is driven by low-level visual statistics, not semantic content. Berman speculates that curvature may be a primitive signal for organic forms, which our brains associate with safety and meaning.

Using health data from ~30,000 Toronto residents, tree data from the city (580,000 public trees cataloged by species and trunk diameter), and satellite imagery for backyard trees, Berman's group calculated tree canopy at the neighborhood level. After adjusting for age, education, and income, each additional tree on a city block was associated with a 1% increase in self-reported health perception—an effect comparable to giving every household $10,000 more income or moving them to a neighborhood $10,000 wealthier, or to being 7 years younger. For objective diagnoses, a one-tree-per-neighborhood increase correlated with a 1% reduction in the incidence of stroke, diabetes, and heart disease; the monetary equivalent was $20,000 per household. While not proving causation, the tight demographic controls and the direction of the effect strongly suggest a causal role for trees. Potential mechanisms include improved air quality, encouragement of physical activity, and the direct psychological benefits of viewing nature, which can lower stress hormones and inflammation.

Participants with clinical depression and matched controls were induced to ruminate on a distressing memory before taking a 50-minute walk in nature. Afterwards, the depressed group showed a greater improvement in backwards digit span performance than the non-depressed group. The researchers considered whether nature reduced the amount of rumination, promoted a more distanced (third-person) perspective, or simply boosted directed attention. Their follow-up analyses suggested that the effect was not due to less thinking about problems or to a shift in perspective; instead, nature seemed to increase the available pool of directed attention, enabling better cognitive control over ruminative thoughts. Berman interprets this as nature providing the mental 'fuel' to handle psychological challenges, making it a promising adjunctive intervention for depression and anxiety disorders.

Berman explains that many natural signals (wind, water sounds) are fractal in time—they have a power spectrum where low frequencies have higher amplitude and high frequencies lower amplitude across many timescales. Brain signals (EEG, fMRI) can also be analyzed for temporal fractal structure. Studies show that easier tasks, expert performance, and younger brains exhibit higher temporal fractalness; hard tasks, learning phases, and aging reduce fractalness. This suggests that a high-fractal brain state is energetically efficient and associated with restful, integrative processing. Berman proposes that exposure to fractal-rich natural environments nudges the brain toward this state, effectively recharging directed attention. In contrast, social media and urban noise are periodic or chaotic, driving the brain away from the optimal fractal regime. While still speculative, this framework unifies the spatial compression findings with the restoration of cognitive control.