The study, published in Frontiers in Bird Science, engaged 95 student participants in a randomized, four-treatment, within-subjects experiment conducted entirely outdoors on the NC State campus in Raleigh. Each participant experienced every combination of two landscapes — a restored forest and an urban “gray space” outside the Talley Student Union — paired with two soundscapes: a recording of marsh birdsong and a recording of traffic noise. The design allowed the team to disentangle the visual and auditory components of nature exposure, a question that laboratory studies have explored but that real-world settings rarely permit.

The physiological logic of the experiment rests on two complementary measures. Heart rate, captured with a Polar H10 chest strap, tends to rise with acute stress and sympathetic nervous system arousal. Heart rate variability, quantified here as the root mean square of successive differences between heartbeats (RMSSD), reflects beat-to-beat variation driven by the parasympathetic nervous system. Higher RMSSD values signal greater autonomic flexibility and recovery, while lower values indicate the body remains in a vigilant, fight-or-flight posture. By tracking both metrics simultaneously, the researchers could probe whether nature’s calming influence acts on cardiovascular arousal, autonomic recovery, or both.

The two landscape treatments were carefully matched in structure but opposite in character. The forest site, part of the Rocky Branch Stream Restoration and Greenway Project completed in 2006, offered more than 70 percent closed canopy within a 50-meter radius of the seating area, with no direct forward-facing views of buildings or pavement. The gray space, by contrast, was more than 70 percent built infrastructure, with clear sight lines to surrounding campus buildings. Each session began with five minutes of silence, followed by ten minutes of either birdsong — recorded at a freshwater marsh in Florida’s St. Marks National Wildlife Refuge and dominated by blue-gray gnatcatchers, Carolina wrens, and white-eyed vireos — or traffic noise recorded at a busy intersection near Paris. Participants wore noise-canceling headphones and sat in camp chairs, completing all four treatments over roughly two hours on days when temperatures ranged between 20 and 25 degrees Celsius, a window chosen to minimize thermal confounding.

Analysis with linear mixed-effects models, which included a random intercept for each participant to account for repeated measures, revealed a striking division of labor between the senses. Forest exposure significantly reduced heart rate relative to the gray space (b = 0.65, p = 0.007), and this effect held regardless of whether students heard birdsong, traffic, or silence. Meanwhile, birdsong significantly increased heart rate variability relative to traffic noise (b = -1.38, p = 0.049), again independent of the surrounding landscape. Crucially, the interaction between soundscape and landscape was not statistically significant for either outcome (all p > 0.16), suggesting the visual and auditory benefits did not require each other to manifest.

These results challenge a theoretical framework known as cross-modal congruence, which predicts that mismatched sensory cues — such as hearing birdsong while staring at a parking lot — impose a cognitive cost that diminishes restorative benefits. The NC State team found no evidence of such a penalty. Instead, the data align more closely with an additive model, in which natural landscapes and natural soundscapes each contribute to physiological recovery through partially independent pathways. This interpretation is consistent with stress reduction theory, which holds that humans possess a genetically ingrained affinity for nonthreatening natural settings that historically signaled safety and resource availability.

The mechanistic story the authors propose is elegant. Birdsong, being acoustically predictable and evolutionarily associated with low-threat environments, may reduce vigilance and allow greater parasympathetic activation — the branch of the nervous system responsible for “rest and digest” functions. Traffic noise, by contrast, is unpredictable and evolutionarily linked to human activity and potential danger, sustaining physiological arousal even when listeners report no conscious distress. Forest views, meanwhile, appear to exert a robust influence on cardiovascular activity that persists whether the acoustic backdrop is natural, anthropogenic, or silent, suggesting the visual channel operates on a somewhat different component of autonomic function than the auditory one.

The practical implications for campus and urban design are considerable. Because the benefits of forests and birdsong appear additive rather than synergistic, planners need not wait for the ideal combination of dense canopy and rich avian soundscape to improve student well-being. In areas where traffic noise cannot be fully mitigated, retaining patches of vegetation may still facilitate stress reduction. Conversely, in gray spaces where trees cannot dominate, promoting bird habitat and diversity — which prior research links to lower rates of poor mental health independent of tree cover — could yield meaningful gains. The findings support the broader concept of “nearby nature,” in which even small doses of greenery or birdsong confer health benefits without requiring immersive wilderness experiences.

The study is not without limitations. Treatment durations were relatively brief — 3.5 minutes of control and 8.5 minutes of exposure — whereas some research suggests prolonged exposure exceeding 30 minutes may be needed to reduce certain physiological stress markers. Sound pressure levels at the headphones were not measured, though volume was held constant within participants. The sample, drawn largely from students in nature-focused degree programs, may have exhibited a ceiling effect, with participants already spending substantial time outdoors and thus showing attenuated treatment responses. Future work with more diverse participants, longer exposure windows, and additional biomarkers such as cortisol could clarify whether the observed autonomic benefits generalize and intensify with dose.

Nevertheless, the experiment demonstrates that even brief, accessible encounters with forests and birdsong produce detectable changes in the autonomic nervous system of young adults in an ordinary campus setting. As universities worldwide grapple with rising rates of anxiety and depression among students — approximately 60 percent reported mental health challenges in 2020 — the message from Raleigh is quietly optimistic: the medicine may be as simple as a walk under the canopy or a few minutes of listening to the birds.

Subject of Research: Effects of forest landscapes and birdsong soundscapes on physiological stress in college students

Article Title: Exposure to forests and birdsong may reduce physiological stress among college students

Article References: Ford, T., DeMay, P., Hipp, J. A., Larson, L. R., Desrochers, H. M., Webb, J., Howell, I., Pratiwi, M. A., Meshram, K., Kluttz, J., Foy, E., Barlow, G., McDade, C., Bourke, C. J., Mali, I., Moorman, C. E., & Peterson, M. N. (2026). Exposure to forests and birdsong may reduce physiological stress among college students. Frontiers in Bird Science, 5, Article 1884835. https://doi.org/10.3389/fbirs.2026.1884835

Image Credits: AI Generated

DOI: 10.3389/fbirs.2026.1884835

Keywords: birdsong, heart rate variability, physiological stress, college students, forest exposure, green infrastructure, mental health, soundscape, autonomic nervous system, urban nature, traffic noise, campus design