Was human evolution characterised by intergroup coalitional aggression or small-scale war? A large experimental program has recently documented cognitive signatures of adaptation to such aggression in American samples: automatic and rapid (within 100 ms) attention to threatening coalitions, accurate estimation of their size upon brief exposure (400 ms), and nuanced, input-sensitive assessment of their formidability. Here we tested twelve preregistered predictions, identical to those tested in the US, in representative samples from 30 countries spanning six world regions (N = 15,640). Only two of the twelve effects diverged from the US, and one divergence dissolved once a preregistered non-linearity was modelled. Strikingly, the reproduced effects held in the same direction in most or all of the 30 countries. Formal hierarchical modelling detected cross-country variation in only two of the twelve effects, and even those varied in how steeply, not in whether, the relationship held. Coalitional assessments thus bear the hallmarks of human universals—panhuman cognitive adaptations to recurrent coalitional aggression over evolutionary time scales, not products of any one contemporary culture.

Decades of research support the generalization that human males tend to be more aggressive than females. However, most of that research has examined aggression between unrelated individuals. Data drawn from 24 societies around the globe (n = 4,013) indicate that this generalization does not hold in the context of sibling relationships. In retrospective self-reports, females report being at least as aggressive as males toward their siblings, often more so. This holds for direct as well as indirect aggression, and for aggression between adult siblings as well as aggression that occurred during childhood. Consistent with prior research on sex differences, males reported engaging in more direct aggression toward nonkin than did females in the majority of societies. The results suggest that the dynamics of aggression within the family are different from those outside of it, and ultimately that understanding the role of sex in aggressive tendencies depends on context and target.

Credence goods, such as repair and healthcare services, are characterized by profound information asymmetries between less-informed customers and better-informed expert sellers. These information asymmetries open the door for fraudulent behavior on the seller side. In a preregistered natural field experiment, we vary in one dimension the seller’s perception of whether the service is an ordinary or a credence good service and in the second dimension whether the customer is a member of a minority or a member of the majority. This allows us to measure the size of the induced credence goods markup and to address the question whether it interacts systematically with discrimination. We document the existence of a large credence goods markup, on average. Moreover, we find that members of the minority pay a sizeable discriminatory markup if the good is perceived as a credence good but not if it is perceived as an ordinary good. Our results show that sellers engage in sophisticated discrimination where informational asymmetries are used to hide discriminatory (fraudulent) behavior. With the help of an ex post survey, we derive a possible explanation for our results. This paper was accepted by Maria Claire Villeval, behavioral economics and decision analysis. Funding: Financial support was provided by the Austrian Science Fund [Special Research Area Grant SFB F63 and Grants P26901 and P27912]. Supplemental Material: The online appendices and data files are available at https://doi.org/10.1287/mnsc.2022.02666 .

The Battle of Mosul (2016–2017) was one of the most grueling urban warfare campaigns in recent memory. The fighting quickly concentrated in West Mosul, where civilians prevented by the Islamic State from leaving their homes experienced airstrikes and indiscriminate shelling by government forces. Utilizing the as-if-randomness of severe damage or destruction of people’s homes, this paper examines the impact of war exposure on the endorsement of moral foundations among a large and diverse sample of Mosul residents ( N = 1027). Home damage increased binding morality but had a larger impact on individualizing morality, heightening concerns about fairness and protection from harm. A survey experiment in which the sectarian identity of the target was randomly assigned further revealed a strong association between individualizing morality and parochial altruism. Challenging conventional wisdom, both individualizing and binding morality reinforce group cohesion in ways that are functionally adaptive and responsive to the damage wrought by war.

The experiences of war and trauma have been shown to have many implications for the behavior and attitudes of individuals, including economic and social preferences. It has been argued that this may in part be the result of a process called Post Traumatic Growth (PTG), where individuals exposed to traumatic events experience growth in a number of domains, thereby shifting preferences. However, few studies have actually tested this supposition with field data. I argue that in populations that have experienced trauma such as armed conflict, individuals who experience PTG will display a reduced tendency towards loss-aversion, which individuals in threatening conditions otherwise display. To test my hypotheses, I conduct a survey with over 2000 refugees from the ongoing conflict in Syria, living in the Midyat refugee camp in Mardin, near the Turkish-Syrian border. In addition to reporting individual level trauma, the respondents also complete a hypothetical valuation task. I show that in this conflict-exposed sample, individuals not experiencing PTG displayed stronger responses to losses than to gains. However, individuals with high PTG showed the inverse relationship, with stronger responses to gains than to losses. This has implications for post conflict societies and other contexts where people may have experienced high levels of trauma.

How does psychology vary across human societies? The fundamental social motives framework adopts an evolutionary approach to capture the broad range of human social goals within a taxonomy of ancestrally recurring threats and opportunities. These motives-self-protection, disease avoidance, affiliation, status, mate acquisition, mate retention, and kin care-are high in fitness relevance and everyday salience, yet understudied cross-culturally. Here, we gathered data on these motives in 42 countries (N = 15,915) in two cross-sectional waves, including 19 countries (N = 10,907) for which data were gathered in both waves. Wave 1 was collected from mid-2016 through late 2019 (32 countries, N = 8,998; 3,302 male, 5,585 female; Mage = 24.43, SD = 7.91). Wave 2 was collected from April through November 2020, during the COVID-19 pandemic (29 countries, N = 6,917; 2,249 male, 4,218 female; Mage = 28.59, SD = 11.31). These data can be used to assess differences and similarities in people's fundamental social motives both across and within cultures, at different time points, and in relation to other commonly studied cultural indicators and outcomes.

The COVID-19 pandemic caused drastic social changes for many people, including separation from friends and coworkers, enforced close contact with family, and reductions in mobility. Here we assess the extent to which people's evolutionarily-relevant basic motivations and goals-fundamental social motives such as Affiliation and Kin Care-might have been affected. To address this question, we gathered data on fundamental social motives in 42 countries (N = 15,915) across two waves, including 19 countries (N = 10,907) for which data were gathered both before and during the pandemic (pre-pandemic wave: 32 countries, N = 8998; 3302 male, 5585 female; M-age = 24.43, SD = 7.91; mid-pandemic wave: 29 countries, N = 6917; 2249 male, 4218 female; M-age = 28.59, SD = 11.31). Samples include data collected online (e.g., Prolific, MTurk), at universities, and via community sampling. We found that Disease Avoidance motivation was substantially higher during the pandemic, and that most of the other fundamental social motives showed small, yet significant, differences across waves. Most sensibly, concern with caring for one's children was higher during the pandemic, and concerns with Mate Seeking and Status were lower. Earlier findings showing the prioritization of family motives over mating motives (and even over Disease Avoidance motives) were replicated during the pandemic. Finally, well-being remained positively associated with family-related motives and negatively associated with mating motives during the pandemic, as in the pre-pandemic samples. Our results provide further evidence for the robust primacy of family-related motivations even during this unique disruption of social life.

How does war shape human altruism? Some find warfare increases generosity within groups only. Others maintain that war's prosocial effects extend to outgroup members as well. To make sense of these disparate findings, we offer a theoretical framework that highlights the role of threat sensitivity in altruism. Refugees from Syria and Iraq (N = 1521) completed a welfare tradeoff task and threat perceptions scale where the other's group identity, gender and age were experimentally varied. We found that individuals belonging to social categories associated with more threat (outgroup members, males, and younger individuals) were afforded less altruism compared to individuals belonging to non-threatening social categories (ingroup members, females and the elderly). War exposure enhanced bias against threatening social categories through increased threat-sensitivity. Our results have implications for understanding how warfare shapes altruism and welfare tradeoffs in light of cross-cutting social categories and for policies promoting post-conflict cooperation.

Intergroup interaction can be hindered by legacies of conflict and group biases. Many studies have looked at intergroup attitudes and pro-sociality in the wake of intergroup conflict, but few have explicitly studied how the group affiliation of another person affects the willingness to interact economically, especially when the interactions concern contested issues. In this study, I investigate the effect of group affiliation on the willingness to engage in economic interactions with others among individuals exposed to violent intergroup conflict, using a sample of refugees from the conflicts in Syria and Iraq. Based on the theory of indirect reciprocity, it is predicted that the tradeoff paradigms, that is, the willingness to engage in economic transactions with another individual, will depend on previous actions of other members of that individual's group. Participants tended to adopt a communal sharing tradeoff paradigm with ingroup members, and they tended to adopt a market pricing paradigm with outgroup members. However, this was the case only for those who reported that outgroup members had taken actions to harm them or their family in the conflict. For those who reported being harmed by members of the ingroup, a market pricing paradigm was employed also with ingroup members. The results suggest that group biases and indirect reciprocity after violent conflict do not necessarily arise from group identities alone, but as a function of past interactions with outgroup members.