Leadership solves collective action problems in small-scale societies

Glowacki, Luke; Rueden, Christopher von

doi:10.1098/rstb.2015.0010

Cited by 196 publications

(170 citation statements)

References 106 publications

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“…The fact that the initiation of raiding parties appears to depend on leaders who function as nucleation sites for raids and who attract other participants is consistent with research showing how individual variation within a population can contribute to the resolution of collective action problems (17,20), including in risky, intergroup violence in both humans and chimpanzees (46). Leaders may alter the costs and benefits for others-either by reducing the costs of the raid to other participants (e.g., via setting the time of the raid or by scouting) or by exerting social pressure on others to join (18,(47)(48)(49).…”

Section: Discussionmentioning

confidence: 53%

Formation of raiding parties for intergroup violence is mediated by social network structure

Glowacki

Isakov

Wrangham

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Intergroup violence is common among humans worldwide. To assess how within-group social dynamics contribute to risky, betweengroup conflict, we conducted a 3-y longitudinal study of the formation of raiding parties among the Nyangatom, a group of East African nomadic pastoralists currently engaged in small-scale warfare. We also mapped the social network structure of potential male raiders. Here, we show that the initiation of raids depends on the presence of specific leaders who tend to participate in many raids, to have more friends, and to occupy more central positions in the network. However, despite the different structural position of raid leaders, raid participants are recruited from the whole population, not just from the direct friends of leaders. An individual's decision to participate in a raid is strongly associated with the individual's social network position in relation to other participants. Moreover, nonleaders have a larger total impact on raid participation than leaders, despite leaders' greater connectivity. Thus, we find that leaders matter more for raid initiation than participant mobilization. Social networks may play a role in supporting risky collective action, amplify the emergence of raiding parties, and hence facilitate intergroup violence in small-scale societies.warfare | social networks | collective action | pastoralists | emergence I ntergroup violence is common, worldwide, and harmful. Global annual deaths from large-scale warfare, for example, range from 0.5 to 1 million, and this does not include nonfatal physical and mental injuries (1). A diverse set of approaches has been used to study intergroup violence and warfare. Evolutionary models have credited collective violence with an important role in the development of modern human behavior (2-7), whereas cultural and ecological factors have been shown to influence small and largescale violence (8-13). More recently, there has been increased interest in understanding the dynamics of group-based violence and the social processes that can contribute to it in the setting of insurgent and terrorist groups (14, 15); for example, online records suggests small, self-organizing groups coalesce into larger groups preceding terrorist attacks (16). Warfare has also been studied as a collective action problem-because individuals must mobilize to engage in a group activity with shared gains (e.g., deterrence, territory) and individual risks (e.g., injury, death) (17, 18).Despite these advances, fundamental questions remain about how violent groups are formed, and the extent to which they may self-organize and emerge organically. Theoretical work suggests interindividual differences may be important for initiating and sustaining risky collective action, but empirical evidence in humans supporting this is sparse (19,20). Research in primate behavior provides some clues regarding the emergence of violent intergroup conflict. Wild chimpanzees engage in lethal coalitionary violence against other communities (21), and a few "impact" individuals sh...

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Section: Discussionmentioning

confidence: 53%

Formation of raiding parties for intergroup violence is mediated by social network structure

Glowacki

Isakov

Wrangham

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…In line with these expectations in some human groups, the most aggressive warriors have lower reproductive success than other men, as documented for the horticulturalist/forager Waorani of Ecuador [169] and Nyangatom of Ethiopia [170]. The Cheyenne war chiefs were expected to be killed in combat, and leaders in the Nyangatom of Ethiopia, the Kapauka of New Guinea and the Jie of Uganda all take greater risks in combat [171,172]. The data show that the highest mortality in the US Army in the Iraq war was among First and Second Lieutenants, who typically lead combat patrols [173].…”

Section: (C) Applications To Human Psychologymentioning

confidence: 82%

Collective action problem in heterogeneous groups

Gavrilets

2015

Phil. Trans. R. Soc. B

113

133

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One contribution of 13 to a theme issue 'Solving the puzzle of collective action through inter-individual differences: evidence from primates and humans'. I review the theoretical and experimental literature on the collective action problem in groups whose members differ in various characteristics affecting individual costs, benefits and preferences in collective actions. I focus on evolutionary models that predict how individual efforts and fitnesses, group efforts and the amount of produced collective goods depend on the group's size and heterogeneity, as well as on the benefit and cost functions and parameters. I consider collective actions that aim to overcome the challenges from nature or win competition with neighbouring groups of co-specifics. I show that the largest contributors towards production of collective goods will typically be group members with the highest stake in it or for whom the effort is least costly, or those who have the largest capability or initial endowment. Under some conditions, such group members end up with smaller net pay-offs than the rest of the group. That is, they effectively behave as altruists. With weak nonlinearity in benefit and cost functions, the group effort typically decreases with group size and increases with within-group heterogeneity. With strong nonlinearity in benefit and cost functions, these patterns are reversed. I discuss the implications of theoretical results for animal behaviour, human origins and psychology.

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“…If true, arrangements that enable groups to align their contributions into coordinated fighting should be particularly effective in aggressor groups, thus increasing their success rate. One such arrangement is sequential decision-making (40,41,51), which has been shown to solve collective action problems in public goods provision (40)(41)(42)(43). In such a procedure, one individual moves first, allowing the rest of the group to adapt and follow the first-mover's lead (40,41,43).…”

Section: Methods Summarymentioning

confidence: 99%

In-group defense, out-group aggression, and coordination failures in intergroup conflict

Dreu

Gross

Méder

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

120

144

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Intergroup conflict persists when and because individuals make costly contributions to their group's fighting capacity, but how groups organize contributions into effective collective action remains poorly understood. Here we distinguish between contributions aimed at subordinating out-groups (out-group aggression) from those aimed at defending the in-group against possible out-group aggression (in-group defense). We conducted two experiments in which three-person aggressor groups confronted three-person defender groups in a multiround contest game (n = 276; 92 aggressor-defender contests). Individuals received an endowment from which they could contribute to their group's fighting capacity. Contributions were always wasted, but when the aggressor group's fighting capacity exceeded that of the defender group, the aggressor group acquired the defender group's remaining resources (otherwise, individuals on both sides were left with the remainders of their endowment). In-group defense appeared stronger and better coordinated than out-group aggression, and defender groups survived roughly 70% of the attacks. This low success rate for aggressor groups mirrored that of group-hunting predators such as wolves and chimpanzees (n = 1,382 cases), hostile takeovers in industry (n = 1,637 cases), and interstate conflicts (n = 2,586). Furthermore, whereas peer punishment increased out-group aggression more than in-group defense without affecting success rates (Exp. 1), sequential (vs. simultaneous) decision-making increased coordination of collective action for out-group aggression, doubling the aggressor's success rate (Exp. 2). The relatively high success rate of in-group defense suggests evolutionary and cultural pressures may have favored capacities for cooperation and coordination when the group goal is to defend, rather than to expand, dominate, and exploit.competition | parochial altruism | coordination | collective action | intergroup relations

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Leadership solves collective action problems in small-scale societies

Cited by 196 publications

References 106 publications

Formation of raiding parties for intergroup violence is mediated by social network structure

Formation of raiding parties for intergroup violence is mediated by social network structure

Collective action problem in heterogeneous groups

In-group defense, out-group aggression, and coordination failures in intergroup conflict

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