Self-serving intergroup aggression escalates and prevails over parochial cooperation

Bibliographic Data

ID7154015
AuthorsQinyu Xiao (0000-0002-9824-9247, University of Vienna, corresponding author), Simon Columbu (0000-0003-1546-955X, University of St Andrews), Robert Böhm (0000-0001-6806-0374, University of Vienna)
Year2026
Volume47
Issue1
Pages106801
Publication date2026-01-01
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueEvolution and Human Behavior (JOURNAL)
Journal identifiersISSN: 1090-5138 • E-ISSN: 1879-0607
PublisherElsevier BV (PUBLISHER)
DOI10.1016/j.evolhumbehav.2025.106801
OpenAlexW4416424672
LanguageEN
Citations received1
References cited89

Anthropological evidence suggests that intergroup conflict in small-scale societies frequently involves opportunistic attacks by small groups of raiders. These incursions are low-risk and often offer immediate benefits to their participants; however, they can also fuel cycles of revenge between groups, exposing raiders’ in-group members to counterattacks. The existing experimental literature on intergroup conflict has mostly assumed that conflict participation is individually costly but benefits the in-group, leaving the aforementioned form of intergroup aggression understudied. In this research, we used an economic game paradigm that affords both self-serving intergroup aggression, which we term “individual exploitation,” and self-sacrificial conflict participation to investigate the prevalence and determinants of the former and compare it with the latter. In two incentivised behavioural experiments with UK online participants ( N s = 647 and 272), we found prevalent and escalating individual exploitation – consistent with small-scale warfare in pre-state societies – but little self-sacrificial and cooperative conflict participation. We also show that intragroup comparisons can drive such escalation, and costly peer punishment is largely ineffective in containing individual exploitation and promoting in-group cooperation. Our results imply that understanding the human psychology of intergroup aggression requires more consideration of individual exploitation

Aggression · Conflict resolution research · Conflict theories · Cultural conflict · Group conflict · Evolutionary Game Theory and Cooperation · Experimental Behavioral Economics Studies · Social and Intergroup Psychology

Tools

Open DOIOpen Access