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Uniting against a common enemy: Perceived outgroup threat elicits ingroup cohesion in chimpanzees.

ABSTRACT: Outgroup threat has been identified as an important driver of ingroup cohesion in humans, but the evolutionary origin of such a relationship is unclear. Chimpanzees (Pan troglodytes) in the wild are notably aggressive towards outgroup members but coordinate complex behaviors with many individuals in group hunting and border patrols. One hypothesis claims that these behaviors evolve alongside one another, where outgroup threat selects for ingroup cohesion and group coordination. To test this hypothesis, 5 groups of chimpanzees (N = 29 individuals) were observed after hearing either pant-hoots of unfamiliar wild chimpanzees or control crow vocalizations both in their typical daily environment and in a context of induced feeding competition. We observed a behavioral pattern that was consistent both with increased stress and vigilance (self-directed behaviors increased, play decreased, rest decreased) and increased ingroup cohesion (interindividual proximity decreased, aggression over food decreased, and play during feeding competition increased). These results support the hypothesis that outgroup threat elicits ingroup tolerance in chimpanzees. This suggests that in chimpanzees, like humans, competition between groups fosters group cohesion.

SUBMITTER: Brooks J

PROVIDER: S-EPMC7904213 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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Uniting against a common enemy: Perceived outgroup threat elicits ingroup cohesion in chimpanzees.

Brooks James J Onishi Ena E Clark Isabelle R IR Bohn Manuel M Yamamoto Shinya S

PloS one 20210224 2

Outgroup threat has been identified as an important driver of ingroup cohesion in humans, but the evolutionary origin of such a relationship is unclear. Chimpanzees (Pan troglodytes) in the wild are notably aggressive towards outgroup members but coordinate complex behaviors with many individuals in group hunting and border patrols. One hypothesis claims that these behaviors evolve alongside one another, where outgroup threat selects for ingroup cohesion and group coordination. To test this hypo ...[more]

PMID: 33626062

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Project description:To maintain a positive overall view of their group, people judge likeable ingroup members more favourably and deviant ingroup members more harshly than comparable outgroup members. Research suggests that such derogation of deviant ingroup members aims to restore the image of the group by symbolically excluding so-called 'black sheeps'. We hypothesized that information about a harm-doer's group membership influences observers' justice-seeking reactions. Motives for punishment vary based on whether the goal is to punish past harm-doing (i.e., retributive motives), help harm-doers recognize the harm inflicted and reintegrate into society (i.e., restorative motives), or control harm-doer's future behaviour through incapacitating practices and exclusion from society (i.e., utilitarian motives). We hypothesized that immoral behaviours by ingroup rather than outgroup members jeopardize the group's reputation and therefore activate utilitarian (i.e., exclusion-oriented) motives for punishment. Study 1 (N = 187) confirmed that people displayed more utilitarian motives and less restorative motives when sanctioning an ingroup as opposed to an outgroup harm-doer. Study 2 (N = 122) manipulated typicality to the ingroup. Participants displayed stronger utilitarian (i.e., exclusion-oriented) punishment motives when the harm-doer was presented as a typical ingroup rather than an outgroup member. Study 3 (N = 292) replicated the findings of Studies 1 and 2 and further showed that people displayed stronger utilitarian punishments against an ingroup offender through the experience of increased identity threat. Contrary to our expectations, observers' ingroup identification did not moderate the effect of group membership or typicality to the ingroup on justice reactions. Yet, ingroup identification influenced both experienced identity threat (i.e., mediator) and utilitarian motives for punishment with high identifiers experiencing higher threat and displaying stronger utilitarian punishment motive. We discuss the results in terms of people's concern for the protection of their group identity.

Project description:BackgroundSeveral event related potential (ERP) studies have investigated the time course of different aspects of evaluative processing in social bias research. Various reports suggest that the late positive potential (LPP) is modulated by basic evaluative processes, and some reports suggest that in-/outgroup relative position affects ERP responses. In order to study possible LPP blending between facial race processing and semantic valence (positive or negative words), we recorded ERPs while indigenous and non-indigenous participants who were matched by age and gender performed an implicit association test (IAT). The task involved categorizing faces (ingroup and outgroup) and words (positive and negative). Since our paradigm implies an evaluative task with positive and negative valence association, a frontal distribution of LPPs similar to that found in previous reports was expected. At the same time, we predicted that LPP valence lateralization would be modulated not only by positive/negative associations but also by particular combinations of valence, face stimuli and participant relative position.ResultsResults showed that, during an IAT, indigenous participants with greater behavioral ingroup bias displayed a frontal LPP that was modulated in terms of complex contextual associations involving ethnic group and valence. The LPP was lateralized to the right for negative valence stimuli and to the left for positive valence stimuli. This valence lateralization was influenced by the combination of valence and membership type relevant to compatibility with prejudice toward a minority. Behavioral data from the IAT and an explicit attitudes questionnaire were used to clarify this finding and showed that ingroup bias plays an important role. Both ingroup favoritism and indigenous/non-indigenous differences were consistently present in the data.ConclusionOur results suggest that frontal LPP is elicited by contextual blending of evaluative judgments of in-/outgroup information and positive vs. negative valence association and confirm recent research relating in-/outgroup ERP modulation and frontal LPP. LPP modulation may cohere with implicit measures of attitudes. The convergence of measures that were observed supports the idea that racial and valence evaluations are strongly influenced by context. This result adds to a growing set of evidence concerning contextual sensitivity of different measures of prejudice.

Dataset Information

Uniting against a common enemy: Perceived outgroup threat elicits ingroup cohesion in chimpanzees.

Publications

Uniting against a common enemy: Perceived outgroup threat elicits ingroup cohesion in chimpanzees.

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