Melissa M. McDonald

Evolution and the psychology of intergroup conflict: the male warrior hypothesis

The social science literature contains numerous examples of human tribalism and parochialism—the tendency to categorize individuals on the basis of their group membership, and treat ingroup members benevolently and outgroup members malevolently. We hypothesize that this tribal inclination is an adaptive response to the threat of coalitional aggression and intergroup conflict perpetrated by ‘warrior males’ in both ancestral and modern human environments. Here, we describe how male coalitional aggression could have affected the social psychologies of men and women differently and present preliminary evidence from experimental social psychological studies testing various predictions from the ‘male warrior’ hypothesis. Finally, we discuss the theoretical implications of our research for studying intergroup relations both in humans and non-humans and discuss some practical implications.

Prejudice at the nexus of race and gender: an outgroup male target hypothesis.

Adopting an evolutionary approach to the psychology of race bias, we posit that intergroup conflict perpetrated by male aggressors throughout human evolutionary history has shaped the psychology of modern forms of intergroup bias and that this psychology reflects the unique adaptive problems that differ between men and women in coping with male aggressors from groups other than ones own. Here we report results across 4 studies consistent with this perspective, showing that race bias is moderated by gender differences in traits relevant to threat responses that differ in their adaptive utility between the sexes-namely, aggression and dominance motives for men and fear of sexual coercion for women. These results are consistent with the notion that the psychology of intergroup bias is generated by different psychological systems for men and women, and the results underscore the importance of considering the gender of the outgroup target as well as the gender of the agent in psychological studies on prejudice and discrimination.

Extending the Behavioral Immune System to Political Psychology: Are Political Conservatism and Disgust Sensitivity Really Related?

Previous research suggests that several individual and cultural level attitudes, cognitions, and societal structures may have evolved to mitigate the pathogen threats posed by intergroup interactions. It has been suggested that these anti-pathogen defenses are at the root of conservative political ideology. Here, we test a hypothesis that political conservatism functions as a pathogen-avoidance strategy. Across three studies, we consistently find no relationship between sensitivity to pathogen disgust and multiple measures of political conservatism. These results are contrasted with theoretical perspectives suggesting a relationship between conservatism and pathogen avoidance, and with previous findings of a relationship between conservatism and disgust sensitivity.

Fertility and Intergroup Bias in Racial and Minimal-Group Contexts Evidence for Shared Architecture

Recent research has shown that White women’s bias against Black men increases with elevated fertility across the menstrual cycle. We demonstrate that the association between fertility and intergroup bias is not limited to groups defined by race, but extends to group categories that are minimally defined, and may depend on the extent to which women associate out-group men with physical formidability. In Study 1, Black and White women with strong associations between the racial out-group and physical formidability displayed greater bias against out-group men as conception risk increased. Study 2 replicated these results in a minimal-group paradigm. These findings are consistent with the notion that women may be endowed with a psychological system that generates intergroup bias via mechanisms that rely on categorization heuristics and perceptions of the physical formidability of out-group men, particularly when the costs of sexual coercion are high.

Treating Prejudice With Imagery: Easier Said Than Done?

Exposure therapy, a commonly used treatment for anxiety disorders and phobias, involves exposing the patient to a fear-eliciting stimulus in the context of a safe and supportive environment (Foa & Kozak, 1986). Birtel and Crisp (2012) used this framework to develop a novel “treatment” for prejudice based on the idea that outgroup members are an anxiety-provoking stimulus. Across three studies, anticipatory anxiety about interacting with a stigmatized out-group member (i.e., a person with schizophrenia, a gay man, or a British Muslim) was reduced if participants first imagined a negative interaction followed by a positive interaction, relative to when participants imagined only positive interactions. These results suggest that guided imagery might be a useful tool to reduce prejudice. These findings are also compelling in light of research in neuroscience demonstrating that conditioned fear may not follow the typical pattern of spontaneous recovery after extinction if extinction occurs shortly after reactivation of the fear memory (Schiller et al., 2010). This work suggests that the activation of emotional memories produces a reconsolidation window in which stored memories are capable of being updated with new information. Given this convergence of theory and empirical findings, as well as the societal importance of reducing prejudice, we attempted to independently replicate Birtel and Crisp’s findings from Studies 1 and 2a. Moreover, it is critically important to replicate and establish precise effect-size estimates when research findings may be used as treatment interventions. The effect sizes obtained by Birtel and Crisp for Studies 1 and 2a (ds = 0.76–1.08; see Table 1) are larger than those reported in other prejudice-reduction studies (e.g., r = .215, d = 0.43; Pettigrew & Tropp, 2006). Precise estimates require large sample sizes (Cumming, 2012), but Birtel and Crisp recruited small samples of 29 participants (Study 1) and 32 participants (Study 2a). Therefore, we followed Simonsohn’s (2013) recommendation that replication studies use samples that are at least 2.5 times the size of the original samples.

Intergroup emotional similarity reduces dehumanization and promotes conciliatory attitudes in prolonged conflict

Creating a sense of interpersonal similarity of attitudes and values is associated with increased attraction and liking. Applying these findings in an intergroup setting, though, has yielded mixed support. Theorizing from a social identity perspective suggests that highlighting intergroup similarity may lead to increased antipathy to the extent that it is perceived as a threat to one’s unique social identity. To circumvent this process, we examine the influence of emotional similarity, rather than attitudinal or value similarity, with the expectation that the short-term nature of emotions may evoke less threat to one’s social identity. Moreover, given the importance of emotions in intergroup humanization processes, we expected that emotional similarity would be associated with greater conciliatory attitudes due to an increase in humanization of the outgroup. We report results from two studies supporting these predictions. Following exposure to an anger-eliciting news story, Jewish Israeli participants were given information that their own emotional reaction to the story was similar (or not) to an individual member of the outgroup (Study 1: Palestinian citizen of Israel) or the outgroup as a whole (Study 2: Palestinians of the West Bank). As predicted, emotional similarity was associated with increased humanization of the outgroup, and a subsequent increase in one’s willingness to support conciliatory political policies toward the outgroup. We conclude that emotional similarity may be a productive avenue for future intergroup interventions, particularly between groups where differences in attitudes and values are foundational to the intergroup conflict.

Promoting Intergroup Openness and Support for Equality in a New Cultural Context: Replicating the Effects of Internal Criticism

ABSTRACT Exposure to an outgroup member voicing criticism of his or her own group fosters greater openness to the outgroup’s perspective. Research suggests that this effect owes its influence to a serial process in which participants’ perception of the risk involved in voicing internal criticism leads to an increase in the perceived credibility of the speaker. The credibility makes it possible for the speaker to be viewed as open-minded, which subsequently inspires greater hope. This process culminates in an increased openness to the outgroup. These findings have been restricted to the Israeli-Palestinian conflict, but here we examine their generalizability to racial conflict in the United States. Results reveal that White Americans exposed to internal criticism expressed by a Black authority figure express greater openness to African-American perspectives on race relations and are more willing to support policies of racial equality. Replicating past research, this effect is serially mediated by risk, credibility, and hope.

Examining the Link Between Conception Risk and Intergroup Bias: The Importance of Conceptual Coherence

Evolutionary approaches to intergroup bias have predominantly focused on male perpetrators of bias (e.g., Sidanius & Pratto, 1999; Van Vugt, De Cremer, & Janssen, 2007; Wrangham & Peterson, 1996). However, recent research has examined how the motivations for intergroup bias may differ between men and women, providing evidence for a female-specific psychology of prejudice against out-group men that is linked to changes in conception risk across the menstrual cycle (McDonald, Asher, Kerr, & Navarrete, 2011; Navarrete, Fessler, Fleischman, & Geyer, 2009). Hawkins, Fitzgerald, and Nosek (2015) reported a putative failure to confirm this link in a series of replication attempts. Here, we offer three important critiques of their replication attempts that should help clarify these apparent inconsistencies. The most important critique involves the theoretical coherence of the conceptual replications—specifically, the use of female target stimuli in research purportedly aimed at investigating the workings of a psychological system for the avoidance of sexual coercion. Our Commentary is intended to improve understanding of the theoretical arguments underlying key predictions in order to facilitate the continued coherence of research in this important area.

Sexual Selection and the Psychology of Intergroup Conflict

Intergroup conflict perpetrated by male aggressors throughout human evolutionary history is likely to have shaped psychological systems at the foundations of modern forms of intergroup conflict. We posit that sexual selection processes operating at both intra- and intersexual levels have shaped psychological biases in intergroup relations, and that these biases reflect the unique adaptive problems that differ between men and women in coping with male aggressors from groups other than one’s own. Here we survey wide-ranging evidence across disciplines consistent with this perspective. In doing so, we pay special attention to emerging research within social, personality, and evolutionary psychology showing that (a) males are the primary targets and agents of group-based animus and competitive striving, and that (b) intergroup prejudice is modulated by gender differences in psychological traits or states relevant to threat responses that differ in their adaptive utility between the sexes—namely, aggressive dominance motives for men and the avoidance of sexual coercion for women. Implications for a sex-specific, evolved psychology of intergroup conflict are discussed.

Faustian bargains for minorities within group-based hierarchies

A dual-audience signaling problem framework provides a deeper understanding of the perpetuation of group-based inequality. We describe a model of underachievement among minority youth that posits a necessary trade-off between academic success and peer social support that creates a dilemma not typically encountered by nonminorities. Preliminary evidence consistent with the approach is discussed. Such strategic agent perspectives complement the psychological approach put forth by Dixon et al., but with minimal ancillary assumptions.