Neural substrates of male parochial altruism are modulated by testosterone and behavioral strategy

Effects of Ingroup Identification on Ingroup Favouritism during Fairness Norm Enforcement

People tend to voluntarily sacrifice their own interests to reject unfair proposals, and this behaviour is affected by group affiliation. While group bias is a well-established phenomenon, its direction is still unclear, and little attention has been given to possible moderating factors. In two studies, we manipulate participants' ingroup identification and investigate whether and how individuals with various levels of ingroup identification react differently to unfairness from ingroups and outgroups during an incentivized (Study 1, N = 46) and hypothetical (Study 2, N = 332) ultimatum game. The results show that participants display a strong preference for their own group. High identifiers tend to accept unfair proposals from ingroups compared to outgroups, whereas this effect is nonsignificant for low identifiers, especially for moderately unfair treatment (offer 7:3). Moreover, higher identification tends to be accompanied by higher ingroup positive expectation, which then leads to greater ingroup favouritism for an offer of 7:3. These results imply that ingroup identification can enhance group favouritism during fairness norm enforcement through ingroup positive expectation.

Victim Sensitivity and Proposal Size Modulate the Ingroup Favoritism During Fairness Norm Enforcement

People show a strong aversion to inequality and are willing to sacrifice their own interests to punish violations of fairness norms. Empirical research has found that group membership could influence the fairness judgment and norm enforcement of the individuals but has shown inconsistent findings and has not focused much on the potential moderators. Here, the two studies aimed to investigate whether victim sensitivity and proposal size moderate the impact of group membership on reactions to unfair proposals. In both studies, the participants with different victim sensitivity (low vs. high group) played the hypothetical (Study 1) and incentivized (Study 2) ultimatum game under the intragroup and intergroup condition and indicated their responses to the different proposals. Results showed that, regardless of the victim sensitivity, ingroup member is often given preferential and positive treatment. Low victim sensitive persons are more likely to accept unfair offers from the ingroup than the outgroup, while this effect was attenuated for those with high victim sensitivity, especially for highly ambiguous unfair offers (offer 6:4 in Study 1 and 8:2 in Study 2). Moreover, the ingroup favoritism score for ambiguous unfair offers was smaller for high compared with the victim sensitivity group. Taken together, the victim sensitivity, and proposal size could moderate the ingroup favoritism on responses to unfairness.

Prosociality as a foundation for intergroup conflict

Intergroup conflict can be modeled as a two-level game of strategy in which prosociality can take the form of trust and cooperation within groups or between groups. We review recent work, from our own laboratory and that of others, that shows how biological and sociocultural mechanisms that promote prosocial preferences and beliefs create in-group bounded, parochial cooperation, and, sometimes, parochial competition. We show when and how parochial cooperation and competition intensify rather than mitigate intergroup conflict.

Network Neuroscience and the Adapted Mind: Rethinking the Role of Network Theories in Evolutionary Psychology

Evolutionary psychology is the comprehensive study of cognition and behavior in the light of evolutionary theory, a unifying paradigm integrating a huge diversity of findings across different levels of analysis. Since natural selection shaped the brain into a functionally organized system of interconnected neural structures rather than an aggregate of separate neural organs, the network-based account of anatomo-functional architecture is bound to yield the best mechanistic explanation for how the brain mediates the onset of evolved cognition and adaptive behaviors. While this view of a flexible and highly distributed organization of the brain is more than a century old, it was largely ignored up until recently. Technological advances are only now allowing this approach to find its rightful place in the scientific landscape. Historically, early network theories mostly relied on lesion studies and investigations on white matter circuitry, subject areas that still provide great empirical findings to this day. Thanks to new neuroimaging techniques, the traditional localizationist framework, in which any given cognitive process is thought to be carried out by its dedicated brain structure, is slowly being abandoned in favor of a network-based approach. We argue that there is a special place for network neuroscience in the upcoming quest for the biological basis of information-processing systems identified by evolutionary psychologists. By reviewing history of network theories, and by addressing several theoretical and methodological implications of this view for evolutionary psychologists, we describe the current state of knowledge about human neuroanatomy for those who wish to be mindful of both evolutionary and network neuroscience paradigms.

Is testosterone linked to human aggression? A meta-analytic examination of the relationship between baseline, dynamic, and manipulated testosterone on human aggression

Testosterone is often considered a critical regulator of aggressive behaviour. There is castration/replacement evidence that testosterone indeed drives aggression in some species, but causal evidence in humans is generally lacking and/or-for the few studies that have pharmacologically manipulated testosterone concentrations-inconsistent. More often researchers have examined differences in baseline testosterone concentrations between groups known to differ in aggressiveness (e.g., violent vs non-violent criminals) or within a given sample using a correlational approach. Nevertheless, testosterone is not static but instead fluctuates in response to cues of challenge in the environment, and these challenge-induced fluctuations may more strongly regulate situation-specific aggressive behaviour. Here, we quantitatively summarize literature from all three approaches (baseline, change, and manipulation), providing the most comprehensive meta-analysis of these testosterone-aggression associations/effects in humans to date. Baseline testosterone shared a weak but significant association with aggression (r = 0.054, 95% CIs [0.028, 0.080]), an effect that was stronger and significant in men (r = 0.071, 95% CIs [0.041, 0.101]), but not women (r = 0.002, 95% CIs [-0.041, 0.044]). Changes in T were positively correlated with aggression (r = 0.108, 95% CIs [0.041, 0.174]), an effect that was also stronger and significant in men (r = 0.162, 95% CIs [0.076, 0.246]), but not women (r = 0.010, 95% CIs [-0.090, 0.109]). The causal effects of testosterone on human aggression were weaker yet, and not statistically significant (r = 0.046, 95% CIs [-0.015, 0.108]). We discuss the multiple moderators identified here (e.g., offender status of samples, sex) and elsewhere that may explain these generally weak effects. We also offer suggestions regarding methodology and sample sizes to best capture these associations in future work.

Group Cooperation, Carrying-Capacity Stress, and Intergroup Conflict

Peaceful intergroup relations deteriorate when individuals engage in parochial cooperation and parochial competition. To understand when and why intergroup relations change from peaceful to violent, we present a theoretical framework mapping out the different interdependence structures between groups. According to this framework, cooperation can lead to group expansion and ultimately to carrying-capacity stress. In such cases of endogenously created carrying-capacity stress, intergroup relations are more likely to become negatively interdependent, and parochial competition can emerge as a response. We discuss the cognitive, neural, and hormonal building blocks of parochial cooperation, and conclude that conflict between groups can be the inadvertent consequence of human preparedness - biological and cultural - to solve cooperation problems within groups.

Sex differences in the psychophysiological response to an intergroup conflict

Conflict induces psychophysiological responses, but less is known about responses to intergroup conflict. Intergroup relationships activate social processes, adding complexity to people's physiological responses. This study analyzes the psychophysiological responses to intergroup conflict considering sex differences. Thus, 150 young people were distributed in 50 groups in two conditions (conflict vs. non-conflict). Conflict was created in the interaction between two groups (three people each) in the laboratory. Their responses were compared to a control group. Mood, heart rate variability, cortisol, and testosterone were measured. Results showed that intergroup conflict induced a less pronounced decrease in negative and positive mood, and a reduction in parasympathetic activity (RMSSD of IBI). Moreover, women in conflict showed lower testosterone levels than men in conflict and control women. Finally, women's conflict perception correlated with their psychophysiological response. Results suggest that intergroup conflict induces emotional, cardiovascular, and endocrine responses, and that men and women interpret conflict differently.

Endogenous testosterone correlates with parochial altruism in relation to costly punishment in different social settings

Testosterone plays a key role in shaping human social behavior. Recent findings have linked testosterone to altruistic behavior in economic decision tasks depending on group membership and intergroup competition. The preferential treatment of ingroup members, while aggression and discrimination is directed towards outgroup members, has been referred to as parochial altruism. Here we investigated in two consecutive studies, whether testosterone is associated with parochial altruism depending on individual tendency for costly punishment. In the first study, 61 men performed a single-shot ultimatum game (UG) in a minimal group context, in which they interacted with members of an ingroup and outgroup. In the second study, 34 men performed a single-shot UG in a more realistic group context, in which they responded to the proposals of supporters of six political parties during the German election year 2017. Political parties varied in their social distance to the participants’ favorite party as indicated by an individual ranking. Participants of study 2 also performed a cued recall task, in which they had to decide whether they had already encountered a face during the previous UG (old-new decision). In order to make the UG data of study 2 most comparable to the data of study 1, the rejection rates of several parties were combined according to the social distance ranking they achieved. Parties ranked 1 to 3 formed the relatively close and favored ‘ingroup’ that shared similar political values with the participant (e.g., left wing parties), while the ‘outgroup’ consisted of parties ranked from 4 to 6 with more distant or even antagonistic political views (e.g., conservative to right wing parties). In both studies, results showed a parochial pattern with higher rejection rates made in response to outgroup compared to ingroup offers. Interestingly, across studies higher salivary testosterone was associated with higher rejection rates related to unfair outgroup offers in comparison to the unfair offers made by ingroup members. The present findings suggest that latent intergroup biases during decision-making may be positively related to endogenous testosterone. Similar to previous evidence that already indicated a role of testosterone in shaping male parochial altruism in male soccer fans, these data underscore the general, yet rather subtle role of male testosterone also in other social settings.

Neural bases of ingroup altruistic motivation in soccer fans

Humans have a strong need to belong to social groups and a natural inclination to benefit ingroup members. Although the psychological mechanisms behind human prosociality have extensively been studied, the specific neural systems bridging group belongingness and altruistic motivation remain to be identified. Here, we used soccer fandom as an ecological framing of group membership to investigate the neural mechanisms underlying ingroup altruistic behaviour in male fans using event-related functional magnetic resonance. We designed an effort measure based on handgrip strength to assess the motivation to earn money (i) for oneself, (ii) for anonymous ingroup fans, or (iii) for a neutral group of anonymous non-fans. While overlapping valuation signals in the medial orbitofrontal cortex (mOFC) were observed for the three conditions, the subgenual cingulate cortex (SCC) exhibited increased functional connectivity with the mOFC as well as stronger hemodynamic responses for ingroup versus outgroup decisions. These findings indicate a key role for the SCC, a region previously implicated in altruistic decisions and group affiliation, in dovetailing altruistic motivations with neural valuation systems in real-life ingroup behaviour.