Editorial: Parochial Altruism: Pitfalls and Prospects

Cooperating with the outgroup rather than the ingroup: The effects of status, individual mobility, and group mobility on resource allocation and trust in an interactional game

We describe a team game that implements a social dilemma between ingroup cooperation and defection by self-enriching outgroup exchange. We test hypotheses derived from social identity theory about how group status and belief about individual mobility and group mobility affect exchange behavior. We ran 60 experimental team games between rich and poor groups under one of four experiment conditions in a fully crossed design, manipulating the presence or absence of individual mobility and group mobility beliefs. Each game was played over 10 rounds in which participants generated wealth for self or group by allocating tokens to either the ingroup or outgroup bank or to outgroup individuals. We identify 10 exchange strategies via latent class analysis and show how class membership and resulting perceptions of group trust are predicted by the experimental conditions. The results show that rich status and individual mobility promote defecting exchanges with outgroup individuals, and that behavior under individual mobility beliefs weakens ingroup trust. In contrast, intergroup competition of the group mobility condition did not affect ingroup cooperation versus defection or trust.

The demography of human warfare can drive sex differences in altruism

Recent years have seen great interest in the suggestion that between-group aggression and within-group altruism have coevolved. However, these efforts have neglected the possibility that warfare - via its impact on demography - might influence human social behaviours more widely, not just those directly connected to success in war. Moreover, the potential for sex differences in the demography of warfare to translate into sex differences in social behaviour more generally has remained unexplored. Here, we develop a kin-selection model of altruism performed by men and women for the benefit of their groupmates in a population experiencing intergroup conflict. We find that warfare can promote altruistic, helping behaviours as the additional reproductive opportunities winners obtain in defeated groups decrease harmful competition between kin. Furthermore, we find that sex can be a crucial modulator of altruism, with there being a tendency for the sex that competes more intensely with relatives to behave more altruistically and for the sex that competes more intensely with non-relatives in defeated groups to receive more altruism. In addition, there is also a tendency for the less-dispersing sex to both give and receive more altruism. We discuss implications for our understanding of observed sex differences in cooperation in human societies.

Moral polarization and out-party hostility in the US political context

Affective polarization describes the phenomenon whereby people identifying as Republican or Democrat tend to view opposing partisans negatively and co-partisans positively. Though extensively studied, there remain important gaps in scholarly understanding of affective polarization. In particular, (a) how it relates to the distinct behavioural phenomena of in-party “love” vs. out-party hostility; and (b) to what extent it reflects a generalized evaluative disparity between partisans vs. a domain-specific disparity in evaluation. We report the results of an investigation that bears on both of these questions. Specifically, drawing on recent trends in political science and psychology, we hypothesize that moral polarization—the tendency to view opposing partisans’ moral character negatively, and co-partisans’ moral character positively—will be associated with behavioural hostility towards the out-party. We test this hypothesis in two preregistered studies comprising behavioural measures and large convenience samples of US partisans (combined N = 1354). Our results strike an optimistic chord: Taken together, they suggest that this association is probably small and somewhat tenuous. Though moral polarization itself was large—perhaps exceeding prior estimates of trait affective polarization—even the most morally polarized partisans appeared reluctant to engage in a mild form of out-party hostility. These findings converge with recent evidence that polarization—moral or otherwise—has yet to translate into the average US partisan wanting to express hostile and directly discriminatory behaviour toward their out-party counterparts.