Prosociality as a foundation for intergroup conflict

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Although uniquely destructive and wasteful, intergroup conflict and warfare are not confined to humans. They are seen across a range of group-living species, from social insects, fishes and birds to mammals, including nonhuman primates. With its unique collection of theory, research and review contributions from biology, anthropology and economics, this theme issue provides novel insights into intergroup conflict across taxa. Here, we introduce and organize this theme issue on the origins and consequences of intergroup conflict. We provide a coherent framework by modelling intergroup conflicts as multi-level games of strategy in which individuals within groups cooperate to compete with (individuals in) other groups for scarce resources, such as territory, food, mating opportunities, power and influence. Within this framework, we identify cross-species mechanisms and consequences of (participating in) intergroup conflict. We conclude by highlighting crosscutting innovations in the study of intergroup conflict set forth by individual contributions. These include, among others, insights on how within-group heterogeneities and leadership relate to group conflict, how intergroup conflict shapes social organization and how climate change and environmental degradation transition intergroup relations from peaceful coexistence to violent conflict. This article is part of the theme issue ‘Intergroup conflict across taxa’.

Section: (A) Individual Participation In Group Conflictmentioning

confidence: 99%

Intergroup conflict: origins, dynamics and consequences across taxa

Dreu

Triki

2022

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“…Differential cooperation towards in- and outgroups is mostly driven by differential expectations of future reciprocity, supporting the view that within group cooperation shapes individuals’ group identification [8,9]. Outgroup threat increases cooperation within groups in minimal groups [8] which may be due to individuals’ heightened group identification [10]. However, little is known about the level of ingroup bias in members of natural groups experiencing real-life violent conflict [11–16], and in particular, a comparison of behaviour when facing natural outgroups with or without enmity—as opposed to unidentified strangers—is lacking.…”

Section: Introductionmentioning

confidence: 59%

“…However, especially in uncompetitive settings without salient group identities, most people also show positive concern for the welfare of others [5][6][7]. Differential cooperation towards in-and outgroups is mostly driven by differential expectations of future reciprocity, supporting the view that within group cooperation shapes individuals' group identification [8,9]. Outgroup threat increases cooperation within groups in minimal groups [8] which may be due to individuals' heightened group identification [10].…”

Section: Introductionmentioning

confidence: 99%

Are strangers just enemies you have not yet met? Group homogeneity, not intergroup relations, shapes ingroup bias in three natural groups

Doğan

Glowacki

Rusch

2022

Humans often favour ingroup members over others, a bias that drives discrimination and intergroup conflicts. Hostile relations between groups and homogeneity within groups may affect such ingroup bias. In an experiment with members of three natural groups in Ethiopia, we vary intergroup relations (neutral versus enmity) and exploit the natural variation in the homogeneity of groups (homogeneous versus heterogeneous) to identify their effect on in- and outgroup concerns. We find that ingroup bias largely manifests as positive concern for ingroup members combined with no concern for outgroup members. Enmity has no effect on ingroup bias, whereas ingroup concern is amplified in homogeneous groups. Group homogeneity, thus, is the primary driver of concerns for others in our study’s context. Our results are relevant to understanding the consequences of exclusionary group identities. This article is part of the theme issue ‘Intergroup conflict across taxa’.

“…Making such costly contributions serves the group and can thus be seen as a form of pro-social behaviour towards one's in-group. Indeed, as we [ 2 , 72 ] and others (e.g. [ 1 , 5 , 7 ]) have argued and shown, in many group-living species an individual's conflict participation p i is a function of concern for in-group (henceforth α I ) and out-group interests (henceforth α O ), expected out-group threat (henceforth β ), and compliance with group norms for participation ( viz .…”

Section: Oxytocin and Participation In Group Conflictmentioning

confidence: 99%

Oxytocin has ‘tend-and-defend’ functionality in group conflict across social vertebrates

Triki

Daughters

Dreu

2022

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Across vertebrate species, intergroup conflict confronts individuals with a tension between group interests best served by participation in conflict and personal interest best served by not participating. Here, we identify the neurohormone oxytocin as pivotal to the neurobiological regulation of this tension in distinctly different group-living vertebrates, including fishes, birds, rodents, non-human primates and humans. In the context of intergroup conflict, a review of emerging work on pro-sociality suggests that oxytocin and its fish and birds homologues, isotocin and mesotocin, respectively, can elicit participation in group conflict and aggression. This is because it amplifies (i) concern for the interests of genetically related or culturally similar ‘in-group’ others and (ii) willingness to defend against outside intruders and enemy conspecifics. Across a range of social vertebrates, oxytocin can induce aggressive behaviour to ‘tend-and-defend’ the in-group during intergroup contests. This article is part of the theme issue ‘Intergroup conflict across taxa’.