Adaptations to infer fitness interdependence promote the evolution of cooperation.

The evolution of cooperation is a major question in the biological and behavioral sciences. While most theoretical studies model cooperation in the context of an isolated interaction (e.g., a Prisoner's Dilemma), humans live in heterogeneous social environments, characterized by large variations in fitness interdependence-the extent to which one's fitness is affected by others. Theoretical and experimental work indicates that humans can infer, and respond to, variations in interdependence. In a heterogeneous ancestral environment, these psychological mechanisms to infer fitness interdependence could have provided a selective advantage, allowing individuals to maximize their fitness by deciding when and with whom to cooperate. Yet, to date, the link between cognitive inference, variation in fitness interdependence, and cooperation remains unclear. Here we introduce a theoretical framework to study the evolution of inference and cooperation in heterogeneous social environments, where individuals experience interactions with varying levels of corresponding interests. Using a combination of evolutionary game theory and agent-based modeling, we model the evolution of adaptive agents, who incur a cost to infer interdependence, in populations of fixed-behavior agents who always cooperate or defect. Our results indicate that natural selection could promote the evolution of psychological mechanisms to infer fitness interdependence, provided that there is enough variation in fitness interdependence to offset the cost of inference. Under certain conditions, the fixation of adaptive agents results in higher levels of cooperation. This depends crucially on the type of inference performed and the features of the interdependence landscape.

Intergenerational conflicts of interest and prosocial behavior during the COVID-19 pandemic.

The COVID-19 pandemic presents threats, such as severe disease and economic hardship, to people of different ages. These threats can also be experienced asymmetrically across age groups, which could lead to generational differences in behavioral responses to reduce the spread of the disease. We report a survey conducted across 56 societies (N = 58,641), and tested pre-registered hypotheses about how age relates to (a) perceived personal costs during the pandemic, (b) prosocial COVID-19 responses (e.g., social distancing), and (c) support for behavioral regulations (e.g., mandatory quarantine, vaccination). We further tested whether the relation between age and prosocial COVID-19 responses can be explained by perceived personal costs during the pandemic. Overall, we found that older people perceived more costs of contracting the virus, but less costs in daily life due to the pandemic. However, age displayed no clear, robust associations with prosocial COVID-19 responses and support for behavioral regulations. We discuss the implications of this work for understanding the potential intergenerational conflicts of interest that could occur during the COVID-19 pandemic.

Parochial trust and cooperation across 17 societies.

International challenges such as climate change, poverty, and intergroup conflict require countries to cooperate to solve these complex problems. However, the political tide in many countries has shifted inward, with skepticism and reluctance to cooperate with other countries. Thus, cross-societal investigations are needed to test theory about trust and cooperation within and between groups. We conducted an experimental study in 17 countries designed to test several theories that explain why, who, and where people trust and cooperate more with ingroup members, compared with outgroup members. The experiment involved several interactions in the trust game, either as a trustor or trustee. We manipulated partner group membership in the trust game (ingroup, outgroup, or unknown) and if their reputation was at stake during the interaction. In addition to the standard finding that participants trust and cooperate more with ingroup than outgroup members, we obtained findings that reputational concerns play a decisive role for promoting trust and cooperation universally across societies. Furthermore, men discriminated more in favor of their ingroup than women. Individual differences in cooperative preferences, as measured by social value orientation, predicted cooperation with both ingroup and outgroup members. Finally, we did not find support for three theories about the cross-societal conditions that influence the degree of ingroup favoritism observed across societies (e.g., material security, religiosity, and pathogen stress). We discuss the implications for promoting cooperation within and between countries.

Political Ideology, Trust, and Cooperation: In-group Favoritism among Republicans and Democrats during a US National Election.

Theories suggest that political ideology relates to cooperation, with conservatives being more likely to pursue selfish outcomes, and liberals more likely to pursue egalitarian outcomes. In study 1, we examine how political ideology and political party affiliation (Republican vs. Democrat) predict cooperation with a partner who self-identifies as Republican or Democrat in two samples before (n = 362) and after (n = 366) the 2012 US presidential election. Liberals show slightly more concern for their partners' outcomes compared to conservatives (study 1), and in study 2 this relation is supported by a meta-analysis (r = .15). However, in study 1, political ideology did not relate to cooperation in general. Both Republicans and Democrats extend more cooperation to their in-group relative to the out-group, and this is explained by expectations of cooperation from in-group versus out-group members. We discuss the relation between political ideology and cooperation within and between groups.

Reciprocity Outperforms Conformity to Promote Cooperation.

Evolutionary psychologists have proposed two processes that could give rise to the pervasiveness of human cooperation observed among individuals who are not genetically related: reciprocity and conformity. We tested whether reciprocity outperformed conformity in promoting cooperation, especially when these psychological processes would promote a different cooperative or noncooperative response. To do so, across three studies, we observed participants' cooperation with a partner after learning (a) that their partner had behaved cooperatively (or not) on several previous trials and (b) that their group members had behaved cooperatively (or not) on several previous trials with that same partner. Although we found that people both reciprocate and conform, reciprocity has a stronger influence on cooperation. Moreover, we found that conformity can be partly explained by a concern about one's reputation-a finding that supports a reciprocity framework.

Disgust and Anger Relate to Different Aggressive Responses to Moral Violations.

In response to the same moral violation, some people report experiencing anger, and others report feeling disgust. Do differences in emotional responses to moral violations reflect idiosyncratic differences in the communication of outrage, or do they reflect differences in motivational states? Whereas equivalence accounts suggest that anger and disgust are interchangeable expressions of condemnation, sociofunctional accounts suggest that they have distinct antecedents and consequences. We tested these accounts by investigating whether anger and disgust vary depending on the costs imposed by moral violations and whether they differentially correspond with aggressive tendencies. Results across four studies favor a sociofunctional account: When the target of a moral violation shifts from the self to another person, anger decreases, but disgust increases. Whereas anger is associated with high-cost, direct aggression, disgust is associated with less costly indirect aggression. Finally, whether the target of a moral violation is the self or another person influences direct aggression partially via anger and influences indirect aggression partially via disgust.

Functional Interdependence Theory: An Evolutionary Account of Social Situations.

Social interactions are characterized by distinct forms of interdependence, each of which has unique effects on how behavior unfolds within the interaction. Despite this, little is known about the psychological mechanisms that allow people to detect and respond to the nature of interdependence in any given interaction. We propose that interdependence theory provides clues regarding the structure of interdependence in the human ancestral past. In turn, evolutionary psychology offers a framework for understanding the types of information processing mechanisms that could have been shaped under these recurring conditions. We synthesize and extend these two perspectives to introduce a new theory: functional interdependence theory (FIT). FIT can generate testable hypotheses about the function and structure of the psychological mechanisms for inferring interdependence. This new perspective offers insight into how people initiate and maintain cooperative relationships, select social partners and allies, and identify opportunities to signal social motives.

Intergroup competition may not be needed for shaping group cooperation and cultural group selection.

Because intergroup interactions often are mixed-motive rather than strictly zero-sum, groups often negotiate settlements that enable both cultures to thrive. Moreover, group prosperity rests on in-group love (rather than out-group hate) that emerges also absent intergroup competition or comparison. It follows that cultural group selection (CGS) reflects group effectiveness in organizing in-group trust and cooperation, rather than winning (in)direct intergroup competitions.

Personality, self-control, and welfare-tradeoff ratios in revenge and forgiveness.

We address how trait self-control and trait concern for others relate to the concepts of monitored and intrinsic Welfare Tradeoff Ratios (WTRs), respectively, and how recent work on personality, revenge, and forgiveness are informed by the adaptationist perspective proposed in the target article. We also discuss how the proposed adaptationist perspective provides clues to some previously puzzling findings on revenge.

Inferences about interdependence shape cooperation.

During social interactions in daily life, people possess imperfect knowledge of their interdependence (i.e., how behaviors affect each person's outcomes), and what people infer about their interdependence can shape their behaviors. We review theory and research that suggests people can infer their interdependence with others along several dimensions, including mutual dependence, power, and corresponding-versus-conflicting interests. We discuss how perceptions of interdependence affect how people cooperate and punish others' defection in everyday life. We propose that people understand their interdependence with others through knowledge of the action space, cues during social interactions (e.g., partner behaviors), and priors based on experience. Finally, we describe how learning interdependence could occur through domain-specific and domain-general mechanisms.

Gender differences in cooperation across 20 societies: a meta-analysis.

Past research hypothesized that men and women differ in their tendency to cooperate with strangers in situations that involve a conflict of interests. However, recent empirical research has provided converging evidence that men and women cooperate to a similar extent, and that differences in cooperation can emerge in response to specific situational and societal contexts. Here we analyse six decades of empirical research on human cooperation using social dilemmas (1961-2017, k = 126) conducted across 20 industrialized societies, testing pre-registered hypotheses derived from evolutionary theory and social role theory. Overall, our findings revealed little-to-no evidence for an association between gender and cooperation using different meta-analytic approaches. We did not find within-study differences in cooperation between men and women (d = 0.011, 95% CI [-0.038, 0.060]). However, cooperation was slightly higher across studies with predominantly female samples (k = 972). In addition, contrary to our predictions, gender differences in cooperation did not emerge in response to the degree of conflicting interests in the situation, and societal levels of gender equality and economic development. We discuss the implications of these findings for our understanding of gender differences in cooperation. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.

What we need is theory of human cooperation (and meta-analysis) to bridge the gap between the lab and the wild.

This commentary seeks to clarify the potential discrepancy between lab-based and field data in the use and effectiveness of punishment to promote cooperation by recommending theory that outlines key differences between the lab and field, such as the shadow of the future and degree of information availability. We also discuss a recent meta-analysis (Balliet et al. 2011) that does not support all conclusions outlined in Guala's target article.

Four Puzzles of Reputation-Based Cooperation : Content, Process, Honesty, and Structure.

Research in various disciplines has highlighted that humans are uniquely able to solve the problem of cooperation through the informal mechanisms of reputation and gossip. Reputation coordinates the evaluative judgments of individuals about one another. Direct observation of actions and communication are the essential routes that are used to establish and update reputations. In large groups, where opportunities for direct observation are limited, gossip becomes an important channel to share individual perceptions and evaluations of others that can be used to condition cooperative action. Although reputation and gossip might consequently support large-scale human cooperation, four puzzles need to be resolved to understand the operation of reputation-based mechanisms. First, we need empirical evidence of the processes and content that form reputations and how this may vary cross-culturally. Second, we lack an understanding of how reputation is determined from the muddle of imperfect, biased inputs people receive. Third, coordination between individuals is only possible if reputation sharing and signaling is to a large extent reliable and valid. Communication, however, is not necessarily honest and reliable, so theoretical and empirical work is needed to understand how gossip and reputation can effectively promote cooperation despite the circulation of dishonest gossip. Fourth, reputation is not constructed in a social vacuum; hence we need a better understanding of the way in which the structure of interactions affects the efficiency of gossip for establishing reputations and fostering cooperation.

Prosocial and punishment behaviors in everyday life.

Theory and experiments suggest people have different strategies (1) to condition their prosocial behavior in ways that maximize individual benefits and (2) to punish others who have exploited their own and others' prosocial behaviors. To date, most research testing existing theories has relied on experiments. However, documenting prosocial and punishment behaviors outside of the laboratory via experience sampling and diary methods can yield additional, rich insights. Recent work demonstrates these methods can describe social behaviors in daily life and be used to test theory about how behaviors change across situations and relationships. These methods have exposed discrepancies between what people experience in daily life and the problems researchers want to solve to understand the nature of human prosociality.

The Cooperation Databank: Machine-Readable Science Accelerates Research Synthesis.

Publishing studies using standardized, machine-readable formats will enable machines to perform meta-analyses on demand. To build a semantically enhanced technology that embodies these functions, we developed the Cooperation Databank (CoDa)-a databank that contains 2,636 studies on human cooperation (1958-2017) conducted in 78 societies involving 356,283 participants. Experts annotated these studies along 312 variables, including the quantitative results (13,959 effects). We designed an ontology that defines and relates concepts in cooperation research and that can represent the relationships between results of correlational and experimental studies. We have created a research platform that, given the data set, enables users to retrieve studies that test the relation of variables with cooperation, visualize these study results, and perform (a) meta-analyses, (b) metaregressions, (c) estimates of publication bias, and (d) statistical power analyses for future studies. We leveraged the data set with visualization tools that allow users to explore the ontology of concepts in cooperation research and to plot a citation network of the history of studies. CoDa offers a vision of how publishing studies in a machine-readable format can establish institutions and tools that improve scientific practices and knowledge.

Cross-cultural variation in cooperation: A meta-analysis.

Impersonal cooperation among strangers enables societies to create valuable public goods, such as infrastructure, public services, and democracy. Several factors have been proposed to explain variation in impersonal cooperation across societies, referring to institutions (e.g., rule of law), religion (e.g., belief in God as a third-party punisher), cultural beliefs (e.g., trust) and values (e.g., collectivism), and ecology (e.g., relational mobility). We tested 17 preregistered hypotheses in a meta-analysis of 1,506 studies of impersonal cooperation in social dilemmas (e.g., the Public Goods Game) conducted across 70 societies (k = 2,271), where people make costly decisions to cooperate among strangers. After controlling for 10 study characteristics that can affect the outcome of studies, we found very little cross-societal variation in impersonal cooperation. Categorizing societies into cultural groups explained no variance in cooperation. Similarly, cultural, ancestral, and linguistic distance between societies explained little variance in cooperation. None of the cross-societal factors hypothesized to relate to impersonal cooperation explained variance in cooperation across societies. We replicated these conclusions when meta-analyzing 514 studies across 41 states and nine regions in the United States (k = 783). Thus, we observed that impersonal cooperation occurred in all societies-and to a similar degree across societies-suggesting that prior research may have overemphasized the magnitude of differences between modern societies in impersonal cooperation. We discuss the discrepancy between theory, past empirical research and the meta-analysis, address a limitation of experimental research on cooperation to study culture, and raise possible directions for future research. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Interdependence and cooperation in daily life.

Philosophers and scientists have long debated the nature of human social interactions and the prevalence of mutual dependence, conflict of interests, and power asymmetry in social situations. Yet, there is surprisingly little empirical work documenting the patterns of interdependence that people experience in daily life. We use experience sampling to study how people think about 3 dimensions of interdependence in daily life and how these dimensions relate to cooperation. In Study 1, 139 romantic couples (n = 278) reported on situations experienced with their partner (k = 6,766); in Study 2, individuals (n = 284) reported on situations experienced with any other person (k = 7,248), over the course of 1 week. Across both samples, we found that most social interactions were perceived as containing moderate mutual dependence, equal power, and corresponding interests. When couples reported on the same situation (Study 1), they largely agreed on their experienced interdependence and cooperation, suggesting that their reports reflect an underlying shared reality. In daily interactions across both samples, higher mutual dependence and lower conflict of interests were associated with more cooperation, whereas relative power was not directly related to cooperation. These associations replicated in laboratory experiments (Study 2). In daily life, high mutual dependence and high relative power exacerbated the negative relation between conflict of interests and cooperation. Finally, prevalent patterns of interdependence and the experience of specific interdependent situations affected multiple relationship outcomes. Our findings stress the importance of studying a diverse array of interdependent situations-and especially situations with corresponding interests-to better understand cooperation in daily life. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Erratum: Generosity among the Ik of Uganda - Corrigendum.

[This corrects the article DOI: 10.1017/ehs.2020.22.].

Political ideology, cooperation and national parochialism across 42 nations.

Political ideology has been hypothesized to be associated with cooperation and national parochialism (i.e. greater cooperation with members of one's nation), with liberals thought to have more cooperation with strangers and less national parochialism, compared to conservatives. However, previous findings are limited to few-and predominantly western-nations. Here, we present a large-scale cross-societal experiment that can test hypotheses on the relation between political ideology, cooperation and national parochialism around the globe. To do so, we recruited 18 411 participants from 42 nations. Participants made decisions in a prisoner's dilemma game, and we manipulated the nationality of their interaction partner (national ingroup member, national outgroup member or unidentified stranger). We found that liberals, compared to conservatives, displayed slightly greater cooperation, trust in others and greater identification with the world as a whole. Conservatives, however, identified more strongly with their own nation and displayed slightly greater national parochialism in cooperation. Importantly, the association between political ideology and behaviour was significant in nations characterized by higher wealth, stronger rule of law and better government effectiveness. We discuss the implications of these findings for understanding the association between political ideology and cooperation. This article is part of the theme issue 'The political brain: neurocognitive and computational mechanisms'.