The Impacts of Nature Experience on Human Cognitive Function and Mental Health

Empirical Science as Unwitting Heir to the Anima Mundi Tradition

Gregory Bratman’s doctoral work at Stanford stands at a peculiar crossroads: it is rigorously positivist in method yet profoundly aligned in substance with a tradition it never names. The research program examines how exposure to natural environments — walking among trees, encountering open grassland versus urban infrastructure — measurably alters cognitive function, affect, and the neural substrates of self-referential rumination. Bratman demonstrates that even brief immersions in nature reduce activity in the subgenual prefrontal cortex, the brain region most associated with the repetitive, self-focused negative thought that characterizes depression. This is not a soft finding. It is a neuroimaging result with clinical implications. Yet its deepest resonance is not with clinical psychology but with James Hillman’s 1977 call for “a depth psychology of extraversion” — the radical proposition that psychological depth is not exclusively interior to the subject but lives in the world of things, landscapes, and sensory presences. When Hillman argued that “confining analysis to human subjectivity is a restriction of method that distorts psychological realities,” he was making a philosophical claim. Bratman, without philosophical intent, provides empirical scaffolding for it. The subgenual prefrontal cortex quiets not because the subject has achieved insight, but because the world has done something to the subject. The landscape is the active agent.

Rumination as the Empirical Face of What Depth Psychology Calls the Lost Underworld

The specific psychological variable Bratman isolates — rumination — deserves scrutiny beyond its clinical definition. In cognitive-behavioral terms, rumination is maladaptive self-referential processing: the mind circling its own wounds without resolution. But Hillman, in The Dream and the Underworld, argued that “the pervading, though masked, depression in our civilization is partly a response of the soul to its lost underworld.” When the psyche is deprived of imaginal depth — of sensory encounter with a world that possesses its own interiority — it turns obsessively inward, not toward genuine depth but toward a sterile repetition that mimics depth. Bratman’s finding that nature exposure specifically interrupts rumination is striking in this light. The mechanism is not distraction. Subjects are not entertained out of their depression. Rather, the encounter with natural complexity — the affordances of living form, texture, movement, what Adolf Portmann called the Selbstdarstellung of the living world — appears to re-engage what Hillman termed “participatory awareness.” The self-referential loop breaks because something outside the ego’s orbit has claimed the psyche’s attention. Thomas Moore, drawing on Ficino, prescribed precisely this: “You should walk as often as possible among plants that have a wonderful aroma, spending a considerable amount of time every day among such things.” Moore’s framing is ensouled exercise; Bratman’s is experimental design. They describe the same event from opposite ends of a five-hundred-year tradition.

The Doctrine of Specificity: Not All Nature Is Equal, Not All Exposure Is Healing

One of Bratman’s most consequential contributions is his insistence on differentiating types of nature experience. Not all green environments produce equivalent effects. The quality of the encounter matters — its sensory richness, its degree of biodiversity, its contrast with the built environment. This specificity recalls the Renaissance Doctrine of Signatures that Hillman, following Portmann and the Neoplatonists, endorsed: the principle that “visible markings indicate invisible potencies.” Ficino did not recommend generic outdoor time; he prescribed specific kinds of music, food, landscapes, and climate, calibrated to the individual soul’s condition. Bratman’s research, by distinguishing grassland from scrubland, tree canopy from open field, urban park from wilderness, begins to build the empirical taxonomy that Ficino’s tradition always implied but never quantified. The implication is that nature prescriptions in mental health cannot be generic. A walk through a degraded urban park strip is not equivalent to immersion in old-growth forest, and the difference is not merely aesthetic preference — it registers in neural activation patterns. Robert Sardello’s declaration that “the individual presented himself in the therapy room of the nineteenth century, and during the twentieth the patient suffering breakdown is the world itself” finds its twenty-first-century corollary here: the world’s specific, measurable qualities either heal or fail to heal, and the diagnostics must extend to the landscape itself.

Why the Built Environment Pathologizes: Bratman’s Data Meets Hillman’s Dallas

Bratman’s urban control conditions — subjects walking along traffic-heavy roads — consistently produce worse outcomes on measures of affect, working memory, and rumination. This is not surprising in itself, but it gains force when read alongside Hillman’s analysis of the built environment as psychically symptomatic. In his pivotal anima mundi essay, Hillman described buildings as “anorexic” and “catatonic,” business as “paranoid,” arguing that the built world’s pathology floods into the humans who inhabit it. Bratman’s data provides the physiological correlate: urban environments do not merely fail to heal; they actively intensify the neural patterns associated with depressive rumination. The “vast insensate edifice — the doctrine of a soulless world” that Hillman described is not a metaphor alone. It is an environment that measurably degrades cognitive function. Bratman’s work thus collapses the supposed gap between Hillman’s poetic-philosophical claims and evidence-based psychology. The street, which Hillman said was “where today’s major unconsciousness now lies,” turns out to be where the subgenual prefrontal cortex lights up most intensely.

This work matters for anyone encountering depth psychology today because it demonstrates that the tradition’s core claims about world-soul are not merely beautiful — they are testable, and they survive testing. Bratman never cites Hillman, Ficino, or Moore. He does not need to. His data speaks the language their philosophy predicted. For the depth-psychological reader, Bratman offers something rare: permission to believe that the ensouled world is not a nostalgic fantasy but a measurable reality whose absence has measurable consequences. For the empirical researcher, he offers something equally rare: a dataset that, read with sufficient imagination, opens onto a tradition five centuries deep. No other work in the contemporary nature-and-health literature occupies this exact position — unwitting empiricist of the anima mundi.