Children cooperate more with in-group members than with out-group members in an iterated face-to-face Prisoner's Dilemma Game.

Adults are more likely to cooperate with in-group members than with out-group members in the context of social dilemmas, situations in which self-interest is in conflict with collective interest. This bias has the potential to profoundly shape human cooperation, and therefore it is important to understand when it emerges in development. Here we asked whether 6- to 9-year-old children (N = 146) preferentially cooperate with in-group members in the context of a well-studied social dilemma, the iterated Prisoner's Dilemma Game. We assigned children to minimal groups and paired them with unfamiliar same-age and same-gender peers. Consistent with our predictions, children were more likely to cooperate with in-group members than with out-group members in this minimal group context. This finding adds to the current literature on group bias in children's prosocial behavior by showing that it affects decision making in a context that calls on strategic cooperation. In addition, our analyses revealed an effect of gender, with girls more likely to cooperate than boys regardless of the group membership of their partner. Exploring this gender effect further, we found an interaction between gender and age across condition, with older girls showing less sensitivity to the group membership of their partner than younger girls and with older boys showing more sensitivity to the group membership of the partner than younger boys. Our findings suggest that risky cooperation in the face of social dilemmas is shaped by group bias during childhood, highlighting the potentially deeply rooted ties between cooperation and parochialism in humans.

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.

Age Bias in the Workplace: Cultural Stereotypes and In-Group Favoritism.

Two key theoretical frameworks that explain why people might hold biases for or against a specific age group-cultural stereotypes and in-group favoritism-yield distinct and sometimes contradictory predictions. This study proposes a combined framework drawing on these two theories and then tests hypotheses based on this framework in the workplace context. Using survey data from U.S. employees of two pharmaceutical companies, we evaluated the extent to which respondents attributed characteristics related to innovation or change and reliable performance to other workers based on perceived relative age (the age of the target relative to the age of the respondent). The hypotheses that our combined framework generated were supported, but the results varied by type of characteristic as well as by age of the respondent. We conclude that the combined framework is more predictive of age bias in the workplace than either individual framework alone.

Relational diversity and neighbourhood cohesion. Unpacking variety, balance and in-group size.

Ethnic diversity is typically measured by the well-known Hirschman-Herfindahl Index. This paper discusses the merits of an alternative approach, which is in our view better suited to tease out why and how ethnic diversity matters. The approach consists of two elements. First, all existing diversity indices are non-relational. From the viewpoint of theoretical accounts that attribute negative diversity effects to in-group favoritism and out-group threat, it should however matter whether, given a certain level of overall diversity, an individual belongs to a minority group or to the dominant majority. We therefore decompose diversity by distinguishing the in-group share from the diversity of ethnic out-groups. Second, we show how generalized entropy measures can be used to test which of diversity's two basic dimensions matters most: the variety of groups, or the unequal distribution (balance) of the population over groups. These measures allow us to test different theoretical explanations against each other, because they imply different expectations regarding the effects of in-group size, out-group variety, and out-group balance. We apply these ideas in an analysis of various social cohesion measures across 55 German localities and show that both in-group size and out-group diversity matter. For the native majority as well as for persons of immigration background, the variety component of diversity seems to be more decisive than has formerly been acknowledged. These findings provide little support for group threat and in-group favoritism as the decisive mechanisms behind negative diversity effects, and are most in line with the predictions of theories that emphasize coordination problems, asymmetric preferences, and network closure.

The ontogeny of the motivation that underlies in-group bias.

Humans demonstrate a clear bias toward members of their own group over members of other groups in a variety of ways. It has been argued that the motivation underlying this in-group bias in adults may be favoritism toward one's own group (in-group love), derogation of the out-group (out-group hate), or both. Although some studies have demonstrated in-group bias among children and infants, nothing is known about the underlying motivations of this bias. Using a novel game, we found that in-group love is already present in children of preschool age and can motivate in-group-biased behavior across childhood. In contrast, out-group hate develops only after a child's sixth birthday and is a sufficient motivation for in-group-biased behavior from school age onward. These results help to better identify the motivation that underlies in-group-biased behavior in children.

The conflict of social norms may cause the collapse of cooperation: indirect reciprocity with opposing attitudes towards in-group favoritism.

Indirect reciprocity is a cooperation maintaining mechanism based on the social evaluation of players. Here, we consider the case of a group in which two social norms with opposing attitudes towards in-group favoritism are mixed. One norm, called Bushido (the way of warriors), regards cooperation with outsiders as betrayal, whereas the second norm, called Shonindo (the way of merchants), regards cooperation with outsiders as desirable. Each member of the group, irrespective of being a Bushido or a Shonindo player, is evaluated in two different ways and assigned two different labels: "ally" or "enemy" according to the Bushido evaluation; "good" or "bad" according to the Shonindo evaluation. These labels change in response to the action taken (cooperation or defection) when acting as a donor, as well as the label attached to the recipient. In addition to Bushido players, who cooperate with an ally and defect from an enemy, and Shonindo players, who cooperate with a good recipient and defect from a bad recipient, the group contains a third kind of players--unconditional defectors. The fractions of the three types of players follow the replicator dynamics. If the probability of interacting with outsiders is small, and if the cost-to-benefit ratio of cooperation is low, we observe several important patterns. Each social norm is able to maintain a high level of cooperation when dominant. Bushido and Shonindo players evaluate each other unfavorably and engage in a severe conflict. In the end, only one norm permeates the whole group driving the other to the extinction. When both social norms are equally effective, a rare occurrence of unconditional defectors may lead to a successful invasion.

The Influence of Group Favoritism on Moral Judgment -- Evidence From Event-Related Potential.

When judging the morality of an action, individuals may exhibit a bias stemming from group favoritism. It leads to the expression of different moral evaluations of the same behaviors performed by different social groups. The current study used event-related potentials (ERPs) to investigate the influence of in-group favoritism (in-group vs. homogeneous out-group) and out-group favoritism (in-group vs. high-quality out-group) on moral judgments. Two experiments were conducted, showing a higher moral score of the in-group compared to the homogeneous out-group by participants. ERP data indicated that in-group stimulation triggered larger P2 amplitudes than homogeneous out-group. Additionally, a larger N400-like amplitude, localized to the right hemisphere, was observed during the evaluation of the homogeneous out-group. Significantly, when comparing the in-group to the high-quality out-group, there was no discernible difference in moral scores or ERP amplitudes. Overall, the results indicate that in-group favoritism can affect moral judgments, especially when assessing homogeneous out-groups, but it can be reduced by the characteristics of groups.

Group bias under uncertain environment: A perspective of third-party punishment.

Third-party punishment (TPP) effectively promotes social cooperation and maintains social norms in which equity plays a decisive role. When third-party and players are affiliated with different groups, there are two distinct phenomena-in-group favoritism (IGF) and black sheep effect (BSE)-in a certain environment. Equity loses its function as a benchmark when the environment is uncertain (de Kwaadsteniet et al., 2013). Thus, we hypothesized that individuals have a stronger IGF because there is more room for interpretations of their behaviors when an uncertain environment results in ambiguous social norms. We utilized a common resource dilemma (CRD) to manipulate the environmental uncertainty by varying the range of the resource size: a certain environment is represented by a resource size of fixed tokens (i.e., 500 tokens) and an uncertain one is represented by that of 300 to 700 tokens. Additionally, group affiliation is manipulated by the alumni relation between the third-party and players. The present study revealed that the uncertain environment led to stricter costly punishment. The experiment confirms the IGF rather than the BSE. We found boundary conditions between IGF and out-group derogation (OGD). When the players' harvest was not obviously violated, the size of TPP for a control group without group affiliation manipulation anchored those of the in-group and OGD occurred. Opposite, when the harvest was obviously violated, the size of TPP for the control group anchored those of the out-group and IGF occurred. The gender of the third-party affects its decision to punish, with men anchoring the control group's punishment to the in-group and showing OGD, whereas women anchoring the control group's punishment to the out-group and showing IGF.

Neural basis of in-group bias and prejudices: A systematic meta-analysis.

In-group favoritism and prejudices relate to discriminatory behaviors but, despite decades of research, understanding of their neural correlates has been limited. A systematic coordinate-based meta-analysis of functional magnetic resonance imaging (fMRI) studies (altogether 87 original datasets, n = 2328) was conducted to investigate neural inter-group biases, i.e., responses toward in-group vs. out-group in different contexts. We found inter-group biases in some previously identified brain regions (e.g., the medial prefrontal cortex, insula) but also in many previously non-identified brain regions (e.g., the cerebellum, precentral gyrus). Sub-group analyses indicated that neural correlates of inter-group biases may be mostly context-specific. Regarding different types of group memberships, inter-group bias toward trivial groups was evident only in the cingulate cortex, while inter-group biases toward "real" groups (ethnic, national, or political groups) involved broader sets of brain regions. Additionally, there were heightened neural threat responses toward out-groups' faces and stronger neural empathic responses toward in-groups' suffering. We did not obtain significant publication bias. Overall, the findings provide novel implications for theory and prejudice-reduction interventions.

Dimensions of Work-Related Age Stereotypes and In-Group Favoritism.

Age stereotypes in the context of work take effect in management decisions and leadership behavior. We aimed to comprehensively measure main dimensions of work-related age stereotypes, namely, performance, adaptability, reliability, and warmth, and explored how they vary across age groups, thereby testing predictions of social identity theory and associations with social contact. Three hundred and eighty German nurses aged between 19 and 63 years participated in this study. Older nurses were seen as more competent, less physically strong, and less adaptable, whereas younger nurses were seen as less reliable and less warm. In-group bolstering was observed for both age groups, however, much stronger for older professionals. Besides age, contact quality, the number of very close older colleagues, the perception of aging, and the perception of older people in general were associated with age stereotypes about older nurses. We conclude with a discussion of measures to reduce age stereotypes at work.

Time Pressure and In-group Favoritism in a Minimal Group Paradigm.

Based on the group heuristic model and the model of intuitive cooperation, we hypothesized that in-group favoritism would be conspicuously shown through an intuitive process. To test this hypothesis, we utilized a minimal group paradigm, which is traditionally used in social psychological studies, and manipulated decision time in a one-shot prisoner's dilemma game to compare the cooperative contribution level toward in-group and out-group members under three conditions: intuitive, empathic deliberation, and rational deliberation. Our findings confirmed that in-group favoritism was clearly shown in the intuitive condition only, suggesting that the intuitive cooperation model may only be valid in the context of social exchange with in-group members. Additional analysis also showed that in-group favoritism disappeared for participants who had been forced into empathic or rational deliberation for decision making. The theoretical implications of the findings are discussed.

Implications for the Self Determine Benevolence and Self-Protection in Intergroup Relations.

People often favor groups they belong to over those beyond the in-group boundary. Yet, in-group favoritism does not always occur, and people will sometimes favor an out-group over the in-group. We delineate theoretically when in-group favoritism (i.e., self-protection) and out-group favoritism (i.e., benevolence) should occur. In two experiments, groups' relative status and competence stereotypes were manipulated; groups' outcomes were non-contingent in Experiment 1 and contingent in Experiment 2. When allocating reward, members of a low status group were self-protective, favoring the in-group over the out-group under both non-contingent and contingent outcomes. Those with high status benevolently favored the out-group when outcomes were non-contingent, but were self-protective with contingent outcomes. People were willing to engage in social activities with an out-group member regardless of competence. However, when task collaboration had implications for the self, those with low status preferred competent over less competent out-group members. Traits of high status targets were differentiated by those with low status in both experiments, whereas those with high status differentiated low status members' traits only when outcomes were contingent. A general principle fits the data: the implications of intergroup responses for the self determine benevolence and self-protection. Implications for the Self Determine Benevolence and Self Protection in Intergroup Relations.

Inter-Group Conflict and Cooperation: Field Experiments Before, During and After Sectarian Riots in Northern Ireland.

The idea that cooperative groups out-compete less cooperative groups has been proposed as a theoretical possibility for the evolution of cooperation through cultural group selection. Previous studies have found an association between increased cooperation and exposure to inter-group violence, but most have not been able to identify the specific target of cooperation and are based on correlational data making it difficult to establish causality. In this study we test the hypothesis that inter-group conflict promotes parochial altruism (i.e., in-group altruism and out-group hostility) by using longitudinal data of a real-world measure of cooperation-charity and school donations-sampled before, during and after violent sectarian riots between Catholics and Protestants in Belfast, Northern Ireland. We find that conflict is associated with reductions in all types of cooperation, with reduced donations to a neutral charity, and both in-group and out-group primary schools. After the conflict, both in-group and out-group donations increased again. In this context we find no evidence that inter-group conflict promotes parochial altruism.

Do we harm others even if we don't need to?

Evolutionary explanations of the co-existence of large-scale cooperation and warfare in human societies rest on the hypothesis of parochial altruism, the view that in-group pro-sociality and out-group anti-sociality have co-evolved. We designed an experiment that allows subjects to freely choose between actions that are purely pro-social, purely anti-social, or a combination of the two. We present behavioral evidence on the existence of strong aggression-a pattern of non-strategic behaviors that are welfare-reducing for all individuals (i.e., victims and perpetrators). We also show how strong aggression serves to dynamically stabilize in-group pro-sociality.

Political Conservatives' Affinity for Obedience to Authority Is Loyal, Not Blind.

Liberals and conservatives disagree about obeying authorities, with conservatives holding the more positive views. We suggest that reactions to conservative authorities, rather than to obedience itself, are responsible for the division. Past findings that conservatives favor obedience uniformly confounded obedience with conservative authorities. We break down obedience to authority into its constituent parts to test the divisiveness of each part. The concepts of obedience (Study 1) and authority (Study 2) recruited inferences of conservative authorities, conflating results of simple, seemingly face valid tests of their divisiveness. These results establish necessary features of a valid test, to which Study 3 conforms. Conservatives have the more positive moral views of obedience only when the authorities are conservative (e.g., commanding officers); liberals do when the authorities are liberal (e.g., environmentalists). The two camps agree about obeying ideologically neutral authorities (e.g., office managers). Obedience itself is not ideologically divisive.

Economic and evolutionary hypotheses for cross-population variation in parochialism.

Human populations differ reliably in the degree to which people favor family, friends, and community members over strangers and outsiders. In the last decade, researchers have begun to propose several economic and evolutionary hypotheses for these cross-population differences in parochialism. In this paper, we outline major current theories and review recent attempts to test them. We also discuss the key methodological challenges in assessing these diverse economic and evolutionary theories for cross-population differences in parochialism.