Periodic Reporting for period 4 - ATTACK (Pressured to Attack: How Carrying-Capacity Stress Creates and Shapes Intergroup Conflict)
Reporting period: 2023-02-01 to 2024-07-31
Throughout the history, what has been causing tremendous suffering is groups of people fighting each other. While behavioral science research has advanced our understanding of such intergroup conflict, it has largely focused on micro-level processes within and between groups. Disciplines that employ a more historical perspective like climate studies or political geography report that macro-level pressures due to changes in climate and economic scarcity can go along with social unrest and wars. In our project we addressed two main topics, using archival analyses, field observations, and laboratory experiments:
1. How do the macro-level pressures relate to micro-level group dynamics?
Peaceful co-existence and trade among human groups can be fragile and intergroup relations frequently transition to violent exchange and conflict. Here we specify how exogenous changes in groups’ environment and ensuing carrying-capacity stress can increase individual participation in intergroup conflict, and out-group aggression in particular. In intergroup contest experiments, individuals could contribute private resources to out-group aggression (versus in-group defense). Environmental unpredictability created psychological stress and increased participation in and coordination of out-group attacks. Archival analyses of interstate conflicts showed, likewise, that sovereign states engage in revisionist warfare more when their pre-conflict economic and climatic environment was more unpredictable. Given that participation in conflict is wasteful, environmental unpredictability not only made groups more often victorious but also less wealthy. Macro-level changes in the natural and economic environment can be a root cause of out-group aggression and turn benign intergroup relations violent.
2. What are the neurohormonal and brain mechanisms explaining the link between outside pressures, like carrying-capacity stress, and inclinations to violently aggress outgroups?
To understand when and why intergroup relations change from peaceful to violent, we developed a theoretical framework mapping out the different interdependence structures between groups. According to this framework, cooperation can lead to group expansion and ultimately to carrying-capacity stress. In such cases of endogenously created carrying-capacity stress, intergroup relations are more likely to become negatively interdependent and parochial competition can emerge as a response. Using a range of neuroscience methods we examined the cognitive, neural, and hormonal building blocks of parochial cooperation, and specified the roles of the neurohormones oxytocin and testosterone, and neural activity in the temporoparietal junction and dorsolateral prefrontal cortex as key to parochialism.
1. How do the macro-level pressures relate to micro-level group dynamics?
Peaceful co-existence and trade among human groups can be fragile and intergroup relations frequently transition to violent exchange and conflict. Here we specify how exogenous changes in groups’ environment and ensuing carrying-capacity stress can increase individual participation in intergroup conflict, and out-group aggression in particular. In intergroup contest experiments, individuals could contribute private resources to out-group aggression (versus in-group defense). Environmental unpredictability created psychological stress and increased participation in and coordination of out-group attacks. Archival analyses of interstate conflicts showed, likewise, that sovereign states engage in revisionist warfare more when their pre-conflict economic and climatic environment was more unpredictable. Given that participation in conflict is wasteful, environmental unpredictability not only made groups more often victorious but also less wealthy. Macro-level changes in the natural and economic environment can be a root cause of out-group aggression and turn benign intergroup relations violent.
2. What are the neurohormonal and brain mechanisms explaining the link between outside pressures, like carrying-capacity stress, and inclinations to violently aggress outgroups?
To understand when and why intergroup relations change from peaceful to violent, we developed a theoretical framework mapping out the different interdependence structures between groups. According to this framework, cooperation can lead to group expansion and ultimately to carrying-capacity stress. In such cases of endogenously created carrying-capacity stress, intergroup relations are more likely to become negatively interdependent and parochial competition can emerge as a response. Using a range of neuroscience methods we examined the cognitive, neural, and hormonal building blocks of parochial cooperation, and specified the roles of the neurohormones oxytocin and testosterone, and neural activity in the temporoparietal junction and dorsolateral prefrontal cortex as key to parochialism.
For the project a new laboratory was designed and built for psychophysiological measurement and behavioral experiments. Overall, research projects completed successfully with results supporting the theoretical expectations. In total, the project to date resulted in 42 research and review publications in, among others, Proceedings of the National Academy of Sciences, Nature Communications, Nature Human Behavior, Science Advances, Brain and Behavioral Sciences, Journal of Cognitive Neuroscience, Social Cognitive Affective Neuroscience, Perspectives in Psychological Science, Journal of Experimental Psychology General, and Journal of Personality and Social Psychology. For research publications, data and code have been made publicly available and publications are open access. In addition, the project resulted in a Theme Issue on intergroup conflict across taxa published in Philosophical Transactions of the Royal Society, alongside numerous presentations at international meetings like IMEBES, SPUDM, EASP, and ICSD.
ATTACK uncovered how macro-level pressures shape group dynamics and intergroup relations at the micro-level. Not only does this inform about the root causes of conflict within and between human groups and societies. Findings also can have implications for policy for conflict prevention and mitigating climate risks. For example, our results reveal a two-fold impact of climate threat – increased within-group solidarity alongside heightened propensity to aggressively attack non-threatening groups and communities. Such responses are likely to be observed especially when climate threat pertains to the socio-economic functioning of groups and communities. It follows that targeted aid of communities most directly affected by global warming and climate hazards reduces the likelihood of intergroup conflict and violence, especially if aid is tailored to the specific needs and risks groups and communities confront.
ATTACK also revealed an unanticipated result -- individuals not neccesarily react spiteful to out-groups, and intergroup relations not necessarily gravitate towards conflict and hostility. In one project, for example, we found that individuals are well-able to quickly learn how to constructively create agreements across group boundaries and cultural divides (Rojek-Giffin et al., PNAS, 2023). In another project, we found that giving individuals the opportunity to interact with members of out-groups can reduce parochialism and increase cross-boundary, universal cooperation (Gross et al., Science Adv. 2023; PNAS, 2024). These findings stem optimistic -- intergroup relations not need to polarize -- and open-up for new research into intergroup conflict and cooperation.
ATTACK also revealed an unanticipated result -- individuals not neccesarily react spiteful to out-groups, and intergroup relations not necessarily gravitate towards conflict and hostility. In one project, for example, we found that individuals are well-able to quickly learn how to constructively create agreements across group boundaries and cultural divides (Rojek-Giffin et al., PNAS, 2023). In another project, we found that giving individuals the opportunity to interact with members of out-groups can reduce parochialism and increase cross-boundary, universal cooperation (Gross et al., Science Adv. 2023; PNAS, 2024). These findings stem optimistic -- intergroup relations not need to polarize -- and open-up for new research into intergroup conflict and cooperation.