The Evolution of Intergroup Bias: Perceptions and Attitudes in Rhesus Macaques
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ATTITUDES AND SOCIAL COGNITION The Evolution of Intergroup Bias: Perceptions and Attitudes in Rhesus Macaques Neha Mahajan, Margaret A. Martinez, and Gil Diesendruck Natashya L. Gutierrez Bar-Ilan University Yale University Mahzarin R. Banaji Laurie R. Santos Harvard University Yale University Social psychologists have learned a great deal about the nature of intergroup conflict and the attitudinal and cognitive processes that enable it. Less is known about where these processes come from in the first place. In particular, do our strategies for dealing with other groups emerge in the absence of human-specific experi- ences? One profitable way to answer this question has involved administering tests that are conceptual equivalents of those used with adult humans in other species, thereby exploring the continuity or discontinuity of psychological processes. We examined intergroup preferences in a nonhuman species, the rhesus macaque (Macaca mulatta). We found the first evidence that a nonhuman species automatically distinguishes the faces of members of its own social group from those in other groups and displays greater vigilance toward outgroup members (Experiments 1–3). In addition, we observed that macaques spontaneously associate novel objects with specific social groups and display greater vigilance to objects associated with outgroup members (Experiments 4–5). Finally, we developed a looking time procedure—the Looking Time Implicit Association Test, which resembles the Implicit Association Test (Greenwald & Banaji, 1995)—and we discovered that macaques, like humans, automatically evaluate ingroup members positively and outgroup members negatively (Experiments 6–7). These field studies represent the first controlled experiments to examine the presence of intergroup attitudes in a nonhuman species. As such, these studies suggest that the architecture of the mind that enables the formation of these biases may be rooted in phylogenetically ancient mechanisms. Keywords: intergroup bias, comparative cognition, rhesus monkeys Innumerable conflicts around the world, now and in our history, underlying processes that fuel prejudice, hatred, and even large- involve groups demarcated along often-arbitrary social dimensions scale genocide are universal. For this reason, social psychologists such as race/ethnicity, nationality, class, and religion. Although the have devoted much effort to understanding the roots of human political circumstances and putative causes of conflict vary, the intergroup conflict by studying the cognitive and affective pro- cesses that lead to such conflict. The emergence of intergroup preferences—specifically, a bias toward those within one’s group This article was published Online First January 31, 2011. and against those outside of one’s group—has been singled out as Neha Mahajan, Margaret A. Martinez, Natashya L. Gutierrez, and Laurie R. an important aspect of understanding intergroup relations. Santos, Department of Psychology, Yale University; Gil Diesendruck, Department Over the past few decades, social psychologists have gained of Psychology and Gonda Brain Research Center, Bar-Ilan University, Ramat- much insight into both the motivations and cognitive mechanisms Gan, Israel; Mahzarin R. Banaji, Department of Psychology, Harvard University. that underlie intergroup biases in adults (see reviews in Brewer, The contents of this article are solely the responsibility of the authors and do 1991; Fiske, 1998; Miller & Prentice, 1999; Sidanius, 1993; Tajfel not necessarily represent the official views of the National Center for Research & Turner, 1979). By comparison, relatively little effort has been Resources (NCRR) or the National Institutes of Health. The Cayo Santiago devoted to understanding how adult humans come to have these Field Station was supported by NCRR Grant CM-5 P40 RR003640-20. We biases in the first place, both in terms of individual development thank Samuel Post, Jennifer Barnes, Riana Betzler, Marianne Horn, and Kelly and in terms of phylogeny (see Banaji & Heiphetz, 2010). Do Hughes for their help running these studies. We also thank Adaris Mas Rivera and James Ayala for their support at the Cayo Santiago Field Station. intergroup biases emerge because of uniquely human cognitive Correspondence concerning this article and requests for materials should capacities for noticing group differences, building stories around be addressed to Neha Mahajan or to Laurie R. Santos, 2 Hillhouse Avenue, group differences, and rationalizing actions that promote ingroup Department of Psychology, Yale University, New Haven, CT 06520. benefits? Do they require human-specific motivational processes, E-mail: [email protected] or [email protected] such as a fear of death (Pyszczynski, Greenberg, & Solomon, Journal of Personality and Social Psychology, 2011, Vol. 100, No. 3, 387–405 © 2011 American Psychological Association 0022-3514/11/$12.00 DOI: 10.1037/a0022459 387 388 MAHAJAN ET AL. 1997, 1999) or a need to justify the system (Jost & Banaji, 1994)? processes, they would make different predictions about the emer- Do such biases require specific experiences that are a part of gence of intergroup biases, namely that such biases may emerge human development to emerge? Or do they demonstrate continuity early in development and in creatures that lack language or ad- across species, emerge early in development, and require minimal vanced cognitive control capacities. environmental input? For these reasons, studying the origins of intergroup biases— Although little work to date has addressed these questions both developmentally and evolutionarily—may provide an impor- empirically, claims about origins are implicit in a number of the tant way to arbitrate between different theoretical accounts of how major theoretical debates about the nature of intergroup prefer- these biases work. Unfortunately, the majority of empirical re- ences. Take, for example, recent theories that emphasize the role of search on intergroup biases to date has used adult humans as its motivations in promoting intergroup biases (e.g., system justifica- test population. To fully understand the origins of intergroup tion theory: Jost & Banaji, 1994; terror management theory: Pyszc- biases, researchers can turn to two subject populations—young zynski et al., 1997, 1999; optimal distinctiveness theory: Brewer, human infants and children, who have not yet developed the 1991, 1999, 2001, 2003). Such theories emphasize that intergroup sophisticated cognitive capacities of human adults, and nonhuman biases result from complex underlying motivations—ones that primates, who by nature will never develop such capacities. stem from anxieties about existential concerns (Jost & Banaji, By using such a combined comparative–developmental ap- 1994; Pyszczynski et al., 1997, 1999) or the competition between proach, social psychologists will be able to specifically test the distinctiveness and assimilation motives (Brewer, 1991, 1999, extent to which different kinds of human experiences are necessary 2001, 2003). Although these motivations are thought to work for the development of intergroup cognitive processes. In fact, unconsciously, they necessarily rely on rather cognitively ad- studies employing comparative and developmental approaches vanced capacities—a realization of death (e.g., Pyszczynski et al., have yielded new insight into social psychological processes in 1997), the capacity to recognize uncertainty (e.g., Jost & Banaji, other domains, such as the development of prosocial behavior (see 1994), and a sense of self (Brewer, 1991; see also social identity review in Brosnan, 2006; Warneken & Tomasello, 2009), the theory; Abrams & Hogg, 2001; Hogg, 2000; Tajfel & Turner, emergence of judgment and decision-making biases (Brosnan et 1979; Taylor & Moghaddam, 1994). In this way, a strong reading al., 2007; Chen, Lakshminaryanan, & Santos, 2006; Lakshminary- of these theories with motivational components (at least implicitly) anan, Chen, & Santos, 2008; Santos, 2008; Santos & Hughes, predicts that for intergroup biases to emerge, it may be necessary 2009; Santos & Lakshminaryanan, 2008), the origins of cognitive for individuals to have gone through the development of processes dissonance (Aronson & Carlsmith, 1963; Egan, Bloom, & Santos, such as a realization of death, a sense of self, and so forth. In 2010; Egan, Santos, & Bloom, 2007), the development of social addition, these biases should only be present in organisms sophis- evaluation (Hamlin, Wynn, & Bloom, 2007), the emergence of our ticated enough to understand these existential and self-relevant belief in a just world (Olson, Dunham, Dweck, Spelke, & Banaji, concerns. In contrast, other motivational accounts would predict 2008), and intergroup perception (Baron & Banaji, 2006). that humans might not be unique in their intergroup biases. Social We first review what researchers have learned to date about the dominance theory (e.g., Pratto, Sidanius, Stallworth, & Malle, origins of intergroup biases, most of which pursues this question 1994; Sidanius, 1993; Sidanius & Pratto, 1993, 2001), for exam- from a developmental perspective. We then discuss the nature of ple, argues that intergroup biases stem from group-living motiva- grouping in nonhuman primate species and how investigating tions for survival, ones that promote hierarchy and competition. intergroup processes in nonhuman populations can provide spe- This view would predict that other group-living species with cific insights