Groundbreaking research from Heinrich Heine University Düsseldorf has illuminated the double-edged effects of stress: while it binds people more closely to their in-group, it simultaneously drives hostility toward perceived outsiders. Published this week in the Proceedings of the National Academy of Sciences, the findings provide a nuanced neurobiological perspective on why group conflicts—even when costly to all—remain so persistent worldwide. This research offers valuable insights into the psychological forces underpinning social divisions, with implications for Thai society and global communities navigating rising polarization.
In this study, a team led by the Comparative Psychology department at the German university sought to unravel the neurochemical roots of intergroup behavior. The research, with support from clinical neuroscience experts at University Hospital Düsseldorf, involved a carefully structured psychopharmacological experiment: participants received either hydrocortisone (mimicking the stress hormone cortisol), Yohimbin (which boosts the neurotransmitter noradrenaline), both, or a placebo. Placed into groups, the participants competed in economic games for real financial stakes, simulating real-life scenarios of group cooperation and rivalry.
The experimental design centered around “in-groups” and “out-groups”—a concept that resonates in Thai cultural and historical contexts. Each participant could choose to keep money, boost their group’s wealth at personal expense, or simultaneously benefit their group while causing loss to a rival group. Notably, any loss inflicted on outsiders occurred only if it also supported the participant’s own group, a dynamic reflecting the often intertwined motives of loyalty and rivalry in social conflict.
Key findings from the study shed light on how the body’s stress response influences social patterns. According to the research, cortisol significantly increased cooperative behavior within one’s own group, strengthening group bonds even when it involved a personal cost. In contrast, heightened noradrenaline levels boosted aggressive actions aimed at rival groups, even if it meant sacrificing personal financial gain. As Professor Kalenscher, leader of the study, explained, “Stress does not make you aggressive or cooperative in general. Depending on which neurochemical pathway prevails in the physiological stress response, and who you are dealing with—friend or foe—one of the two behavioral patterns can dominate” (medicalxpress.com).
The researchers argue that these patterns offer a neurobiological explanation for the “us versus them” mentality observed across societies. While some level of group belonging is essential and beneficial—mirrored in workplace teams, sports clubs, and family networks in Thailand—the same mechanisms can fuel counterproductive rivalries, as seen during periods of social or political unrest. For Thais, the findings provide a new lens through which to interpret long-standing regional, social, and political divides.
This study brings to mind historic moments when group identities shaped the nation’s trajectory. For instance, tensions between rural and urban populations or political partisanship echo the stress-driven loyalty and hostility highlighted by the researchers. Understanding the biochemical underpinnings of these dynamics may help Thai leaders, educators, and community organisers craft interventions that reduce unnecessary conflict while harnessing the strengths of group solidarity.
Internationally, the study’s implications reach into current events, where polarization and intergroup hostility appear to be on the rise—from global protest movements to digital echo chambers stoked by social media. The research suggests that high-stress environments—whether induced by economic uncertainty, competition, or fear—may push people to cling more tightly to familiar groups and regard outsiders with greater suspicion or open animosity.
Expert commentary situates these findings within a broader scientific context. Social psychologists have long known that stress can either divide or unite, but the clear demonstration that specific neurochemicals drive these effects sharpens the picture. As Professor Kalenscher’s team states, understanding which pathways prevail under stress could help explain dramatic shifts in group behavior—ranging from sudden bursts of community heroism in crises like floods, to outbreaks of mob hostility in contentious protest settings.
For Thailand, this scientific insight calls for practical responses in multiple sectors. In education, for example, curriculums could teach about the neurological roots of stereotyping and prejudice, fostering empathy across regional and social divides. Meanwhile, health professionals might consider how collective stress—during disease outbreaks or economic hardship—impacts not just individual well-being but also social cohesion and conflict. Policymakers could also design stress-reducing community programs as a foundation for building social trust and reducing polarization.
Practically, Thai readers can take away several actionable insights from this research:
- Recognize moments of stress as opportunities to consciously build bridges rather than reinforce divisions.
- Participate in group activities that foster cooperation but keep an open mind toward outsiders, counteracting the instinct to exclude.
- Remain aware that social media and news can amplify stress and, potentially, intergroup hostility—taking intentional breaks can help maintain perspective.
- In workplaces, schools, and communities, leaders should provide safe spaces for dialogue and stress reduction, especially in times of crisis.
In the broader scheme, these findings underscore the value of mindfulness, self-awareness, and open communication in combatting the negative effects of stress on intergroup relations. For Thai society, where group harmony is prized but conflicts do arise, adopting science-based approaches may help build a more inclusive national identity.
For more information on the neurobiological mechanisms of stress and group behaviour, see the full study as reported by medicalxpress.com. Further reading on group psychology and stress in Thai society can be found in the Journal of the Psychiatric Association of Thailand and other academic outlets.