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Cited by 2Experimental Behavioral Economics StudiesEvolutionary Game Theory and CooperationSocial and Intergroup Psychology

Self-serving intergroup aggression escalates and prevails over parochial cooperation

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Xiao, Qinyu, Columbus, Simon, Böhm, Robert·2026·Evolution and Human Behavior
DOI 10.1016/j.evolhumbehav.2025.106801
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Abstract

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.

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  • This inclination could have led to a severe disadvantage within the own group, since other group members were afraid of violent retaliation and therefore avoided contact with individual exploiters.

    “This inclination, however, could have led to a severe disadvantage within the own group, since other group members were afraid of violent retaliation and therefore avoided contact with individual exploiters.”

    From Durkheim, Indoctrinability and the Moral Ambivalence of Human Sociality (2026) · cites this paper as Xiao et al., 2026

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Authors
Xiao, Q., Columbus, S., & Böhm, R.
Affiliations
  • University of Vienna (AT)
  • University of St Andrews (GB)
Corresponding author
Xiao, Qinyu
ORCID
Venue
Evolution and Human Behavior
Publisher
Elsevier BV
Published
2026-01
Volume
47
Issue
1
Pages
106801
ISSN
1090-5138 (ISSN-L)
DOI
10.1016/j.evolhumbehav.2025.106801
OpenAlex
W4416424672
Cited by
2
References
88
Citations by year
2026: 2
FWCI
2.09
Type
journal article
Language
en
Open access
Licence
Locations
  • Evolution and Human Behavior (publishedVersion, cc-by)
  • OSF Preprints (OSF Preprints) (submittedVersion, cc-by)
Topics
  • Social Sciences › Safety Research › Experimental Behavioral Economics Studies
  • Social Sciences › Sociology and Political Science › Evolutionary Game Theory and Cooperation
  • Social Sciences › Sociology and Political Science › Social and Intergroup Psychology
Keywords
intergroup aggression, intergroup conflict, revenge cycle, raiding, peer punishment, conflict escalation, small-scale warfare, pre-state societies, in-group cooperation

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