Environmental Cues as Signals of Social Trust
The residential built environment serves as a complex signalling system that communicates crucial social information to both residents and visitors. As Daniel Nettle (2015) observed, "The perception that others are not trusting and do not help spreads from person to person through the cues they leave in the environment. Those cues are not just in the broken windows and litter on the streets." This observation opens a fascinating window into how evolved psychological mechanisms interact with our modern built environments to produce significant effects on social behaviour and physiological health.
To fully understand these dynamics, it is helpful to draw on three complementary theoretical frameworks: (1) Wilson and O’Brien’s Community Perception, (2) Coan and colleagues’ Social Baseline Theory (SBT), and (3) Brosschot and colleagues’ Generalized Unsafety Theory of Stress (GUTS). Each theory sheds new light on distinct aspects of how humans perceive environmental cues and regulate social and physiological responses. Together, they offer a unified, evolutionarily informed perspective on the built environment—highlighting how environmental cues shape social behaviour, influence stress physiology, and ultimately affect health outcomes.
(1) Community Perception as an Adaptive Mechanism
Wilson and O'Brien (2011) introduced the construct of "Community Perception" to describe a hypothesised adaptive cognitive mechanism that evolved in our ultrasocial species. Their research in Binghamton, New York, demonstrated that humans can rapidly and accurately assess the social quality of unfamiliar neighbourhoods using only visual information from the physical environment.
From an evolutionary perspective, this ability makes adaptive sense. For a species that evolved in small, cohesive social groups but occasionally needed to navigate unfamiliar territories, the capacity to quickly infer the nature of potential social encounters would confer significant survival advantages. What Wilson and O'Brien identified as particularly salient was the level of effort invested in environmental maintenance—essentially, how much care residents demonstrate toward their shared physical space.
Importantly, these environmental assessments influence subsequent social behaviour. When participants believed they were interacting with individuals from neighbourhoods displaying low social quality markers, they exhibited reduced cooperative behaviour in prisoner's dilemma games. This behavioural shift suggests an evolved caution toward individuals who might exploit cooperation without reciprocating, reflecting adaptive mechanisms that protected our ancestors from costly social interactions with untrustworthy partners.
(2) The Social Baseline of Human Physiology
Complementing this framework is Coan and colleagues' Social Baseline Theory (SBT), which posits that the human nervous system evolved to function optimally within a context of social connection rather than isolation (Beckes & Coan, 2011). This theory fundamentally challenges the methodological individualism prevalent in much scientific research, suggesting instead that our baseline physiological state presupposes social embeddedness.
SBT proposes that humans engage in "bioenergetic outsourcing"—essentially distributing the metabolic costs of responding to environmental demands across social networks. The folk wisdom that "a trouble shared is a trouble halved" appears to have a genuine neurobiological basis. Crucially, the quality of social relationships modulates this effect. Trusted others provide greater bioenergetic resources, allowing more efficient regulation of emotional and physiological responses to stressors.
(3) Reframing Stress: From Threat Detection to Safety Perception
The Generalized Unsafety Theory of Stress (GUTS), proposed by Brosschot and colleagues (2018), offers a paradigmatic shift in understanding chronic stress. Rather than conceptualising stress responses as activated by specific threats, GUTS suggests that the stress response is the default state—one that is inhibited only when safety is perceived.
This inversion has profound implications for understanding neighbourhood effects. Traditional approaches assumed that disorder cues actively trigger stress responses. The GUTS framework suggests instead that these cues signify the absence of safety signals, thereby failing to inhibit the default stress response. For an ultra-social species whose safety historically depended on trusted conspecifics, evidence of low social quality in a neighbourhood may represent a fundamental lack of safety signals.
Empirical Evidence: Our Research on Why Maintenance Matters
In our recent study published in Human Ethology (2025), we demonstrated a significant relationship between neighbourhood maintenance and physiological markers of inflammation. Drawing on data from over 9,600 participants in the UK Household Longitudinal Study (Understanding Society), we established a critical association between the residential environment and C-reactive protein (CRP) levels—a key biomarker of inflammatory response and chronic stress exposure.
In our work, we employed a novel methodological approach, developing a Maintenance Index from the study’s metadata to assess environmental conditions whilst controlling for demographic, socioeconomic, housing, and health variables. Our analysis revealed that physical disorder in residential areas appears to function as a chronic stress trigger, potentially contributing to elevated inflammation levels among residents.
We explicitly integrated Wilson and O'Brien's Community Perception theory with Brosschot's Generalized Unsafety Theory of Stress, providing a comprehensive theoretical framework for understanding how environmental cues might trigger physiological stress responses. Our findings suggest that the condition of our built environment has a significant influence on health outcomes through these stress-mediated pathways.
An Integrated Evolutionary Framework
These theoretical perspectives and our empirical findings can be integrated into a coherent evolutionary account of neighbourhood effects. The absence of environmental maintenance serves as a reliable cue about local social dynamics. This cue signals to the observer: "People here lack the capacity or motivation to maintain their shared environment, suggesting diminished availability for prosocial behaviour."
According to the Generalized Unsafety Theory of Stress (GUTS; Brosschot et al., 2018), the human stress response remains chronically active in the absence of safety signals, even without the presence of explicit threats. In line with this framework, the persistent environmental neglect triggers a cascade of physiological and behavioural responses: visitors become less trusting and cooperative, while residents experience sustained stress responses. Over time, this leads to measurable biological effects, such as elevated inflammation markers and increased allostatic load, as reflected in the elevated CRP levels we found in areas with poor maintenance. These physiological changes may ultimately contribute to the development of various health pathologies.
Additionally, the visible evidence of environmental neglect may impose a cognitive and emotional burden on residents through what might be called a "stigmergic" or "sematectonic" mechanism (Heylighen, 2016). These terms, borrowed from the study of eusocial insects, describe how environmental modifications coordinate behaviour across individuals and function as persistent signals within communities. In human contexts, disorder in the environment creates an unrelenting "call to action" that remains unfulfilled—essentially an unaddressed environmental demand for attention. This constant reminder of unresolved problems generates an ongoing psychobiological burden, imposing additional stress on residents already functioning under resource constraints. The result is a feedback loop of environmental strain and physiological response that further compounds the health impacts of neighbourhood disorder.
Implications for Public Health and Urban Policy
Our research demonstrates that neighbourhood maintenance is not merely an aesthetic concern but a significant public health consideration. Our finding that environmental conditions are associated with inflammatory biomarkers suggests a direct pathway through which neighbourhood characteristics may influence physical health outcomes.
For policymakers and urban planners, these findings underscore the importance of investing in the physical upkeep of residential areas, particularly in disadvantaged communities where resources for maintenance may be scarce. Such investments may yield substantial returns in terms of population health and reduced healthcare costs.
In our future research, we plan to continue investigating the specific mechanisms linking neighbourhood conditions to health outcomes. Particularly promising directions include examining additional biomarkers that measure energetic states as well as stress burden, exploring how different stewardship regimes affect outcomes, and conducting longitudinal studies to establish causal relationships more definitively.
Conclusion
An evolutionary lens provides valuable insight into the mechanisms linking neighbourhood characteristics to social behaviour and health outcomes. By understanding these connections as adaptations to our ultrasocial nature, we can better address the complex challenges of creating built environments that support human flourishing.
The effort expended in maintaining our residential environments appears to serve as a powerful social signal—one that communicates fundamental information about the nature and quality of social relations available within a community. Moreover, as our empirical work demonstrates, this signalling system has profound implications for physical health, affecting inflammatory processes that may contribute to numerous chronic diseases.
This integrated perspective on neighbourhood effects—drawing on evolutionary theory, stress physiology, and empirical research—offers a promising framework for addressing persistent health disparities associated with residential environments. By recognising that maintenance matters not just for aesthetics but for fundamental aspects of human physiology, we can develop more effective interventions to promote health equity across diverse communities.
References
Beckes, L., & Coan, J. A. (2011). Social baseline theory: The role of social proximity in emotion and economy of action. Social and Personality Psychology Compass, 5(12), 976-988.
Brosschot, J., Verkuil, B., & Thayer, J. (2018). Generalized unsafety theory of stress: unsafe environments and conditions, and the default stress response. International Journal of Environmental Research and Public Health, 15(3), 464.
Heylighen, F. (2016). Stigmergy as a universal coordination mechanism I: Definition and components. Cognitive Systems Research, 38, 4-13.
McAleavey, D., O'Gorman, R., & Clair, A. (2025). Why Maintenance Matters: Disorder in the Built Environment and Physical Health. Human Ethology, 40(1), 2-17. URL: https://human-ethology.org/article/133698-why-maintenance-matters-disorder-in-the-built-environment-and-physical-health
Nettle, D. (2015). Tyneside Neighbourhoods: Deprivation, Social Life and Social Behaviour in One British City. Cambridge: Open Book Publishers.
O'Brien D. T., & Wilson D. S. (2011). Community perception: the ability to assess the safety of unfamiliar neighbourhoods and respond adaptively. Journal of Personality and Social Psychology. 100, 606–620.
