American Political Science Review (2017) 111, 2, 277–294 doi:10.1017/S0003055416000770 c American Political Science Association 2017 ⃝ The Behavioral Immune System Shapes Political Intuitions: Why and How Individual Differences in Disgust Sensitivity Underlie Opposition to Immigration LENE AARØE University of Aarhus MICHAEL BANG PETERSEN University of Aarhus KEVIN ARCENEAUX Temple University epresent,test,andextendatheoreticalframeworkthatconnectsdisgust,apowerfulbasic human emotion, to political attitudes through psychological mechanisms designed to protect W humans from disease. These mechanisms work outside of conscious awareness, and in modern environments, they can motivate individuals to avoid intergroup contact by opposing immigration. We report a meta-analysis of previous tests in the psychological sciences and conduct, for the first time, a series of tests in nationally representative samples collected in the United States and Denmark that integrate the role of disgust and the behavioral immune system into established models of emotional processing and political attitude formation. In doing so, we offer an explanation for why peaceful integration and interaction between ethnic majority and minorities is so hard to achieve. onventional models of political decision-making inally presented images, for instance, the emotional implicitly assume that citizens form opinions states that they cause influence unrelated decisions C about politics through conscious thought. Even (Brooks et al., 2012). if political attitudes ultimately derive from deep emo- These insights have just begun making inroads into tional attachments to group loyalties developed early political science. Extraneous stimuli, such as music em- in life (Campbell et al. 1960), people nonetheless con- bedded in advertising or images presented outside of sciously survey the considerations that are at the “top conscious awareness, can induce emotional reactions of their heads” at the moment of making a decision that influence political attitudes and evaluations (e.g., (Zaller 1992). The past two decades of research in the Albertson and Gadarian 2015;BanksandValentino neurosciences challenges this simple and intuitive as- 2012;Brader2006;LodgeandTaber2013). From sumption. Much of human decision-making takes place the perspective of conventional models of political outside of conscious awareness (Bargh and Chartrand decision-making, these findings seem like parlor game 1999). The brain nonconsciously processes informa- tricks that fail to capture how people actually form po- tion, automatically imbuing it with emotional content, litical attitudes. Perhaps in a laboratory, the argument allowing only a fraction to reach conscious awareness. could go, people act in strange ways, but automatic pro- Even though people are unaware of “seeing” sublim- cesses should have less influence in real world settings where people have the time and space to engage in conscious reflection. Lene Aarøe is Associate Professor of Political Science, Univer- sity of Aarhus, Bartholins Alle´ 7, 8000 Aarhus C, Denmark However, once we consider that the automatic pro- ([email protected]). cesses in the human mind evolved well before con- Michael Bang Petersen is Professor of Political Science, Uni- scious cognition, it makes sense that the brain should versity of Aarhus, Bartholins Alle´ 7, 8000 Aarhus C, Denmark be quite capable of making complex and important ([email protected]). Kevin Arceneaux is Professor of Political Science, Temple Univer- life-and-death decisions without needing input from sity, 453 Gladfelter Hall, 1115 Polett Walk, Philadelphia, PA 19122 the conscious mind. Indeed, from this perspective, the ([email protected]). automatic processes’ speed and ability to continually Acknowledgements: The research reported in this article was scan the environment are crucial (e.g., Gray 1987). made possible by funding from the Danish Council for Indepen- Over the course of human evolution, the mind was dent Research, the Velux Foundation and the Temple University Behavioral Foundations Lab. The authors would like to acknowl- endowed with many specialized mechanisms designed edge the helpful guidance and advice received from Ted Brader, to deal with recurring threats faced by our ancestors Ryan Enos, Stanley Feldman, John Hibbing, Leonie Huddy, Cindy (Barkow, Cosmides, and Tooby 1992;Cesarioetal. Kam, Robert Kurzban, Richard Lau, Mark Schaller, Jim Sidanius, 2010; Petersen 2015). Because different threats often Kevin Smith, Joshua Tybur, Nicholas Valentino, participants at the Interacting Minds Seminars at Aarhus University, participants in the require unique responses, these mechanisms use differ- American Politics Colloquium at Temple University, participants at ent emotional states—anxiety, disgust, jealousy, etc.— the Human Evolution Lunch Lecture at the Centre for Biocultural to motivate different behaviors (Cottrell and Neuberg History at Aarhus University, participants at Evolutionary Psychol- 2005). In modern democratic societies, a key function ogy Laboratory at Harvard University, participants at the Working of government is to enact policies that provide secu- Group in Political Psychology and Behavior at Harvard University, the anonymous reviewers, as well as APSR co-editors Valerie J. rity and safety from external threats. Thus, there is Martinez-Ebers and Ingo Rohlfing. We are grateful to Dan Nguyen, reason to expect that the deep-seated evolved mecha- Klaus Juul and Julie Joenson for their research assistance. nisms that helped our ancestors defend against threats Received: June 12, 2015; revised: December 7, 2016; accepted: also influence current-day policy preferences (Petersen December 12, 2016. 2015). .AA477CAD645C7:AC:6AC34D:A2CD16AAA076 1/ADA,C4D56A-45C7:-ACCDAD44454277 D645C7:AC:6ACCDD7AAC:1 Lene Aarøe, Michael Bang Petersen, and Kevin Arceneaux In this article, we demonstrate the effects of an im- shapes immigration attitudes (e.g., Faulkner et al. 2004, portant specialized set of mechanisms designed to pro- Green et al. 2010,NavarreteandFessler2006)through tect humans from threats caused by pathogens: the be- ameta-analysis,uncoveringanumberofempiricaland havioral immune system (e.g., Schaller 2006). The be- theoretical gaps. Third, we address these gaps through a havioral component of the immune system works out- suite of observational and experimental studies drawn side conscious awareness (Tybur et al. 2013)anduses from nationally representative samples in the United feelings of disgust to motivate avoidance of potentially States and Denmark. We find consistent evidence that infected objects and people (e.g., Schaller and Neuberg the behavioral immune system shapes immigration at- 2012). Because pathogens can be lethal but extremely titudes over and beyond standard explanations in ex- hard to detect, the behavioral immune system evolved tant political science models: education, ideology, and to be hypervigilant against unfamiliar stimuli, including economic interests. Finally, we consider the broader unfamiliar individuals. In the evolved mind, we argue, implications of the notion that unconscious pathogen- differences in appearance (such as the color of one’s avoidance motivations lead some people to adopt par- skin) are intuitively misinterpreted as cues of infectious ticular political attitudes. Specifically, we demonstrate, diseases, rather than harmless differences in levels of for the first time, how individual differences in the melanin. As the history of institutionalized racial segre- propensity to feel disgust frustrate standard social sci- gation and current day opposition to immigration show, ence approaches to facilitating acceptance of ethnic public discourse readily associates contamination risk differences. We conclude by discussing how the behav- with outgroups, seeking to separate supposedly un- ioral immune system may generate ideological belief clean outgroups from the clean (or “pure”) ingroup. systems that cut across the constraints generated by We investigate the political implications of the be- dominant elite discourse. havioral immune system’s hypervigilance by studying its effect on opposition to immigration. We focus on im- migration, because it is one of the most divisive issues in Western democracies today (e.g., Brader, Valentino, THE BEHAVIORAL IMMUNE SYSTEM AND and Suhay 2008;Citrinetal.1997; Malhotra et al. DISGUST 2013;Snidermanetal.2004). Indeed, the rise of anti- immigration candidates and parties is fundamentally Disease constitutes a fundamental threat to human reshaping the political landscapes in both the United fitness, and the immune system is our most complex States and Europe. In particular, we argue that indi- physiological system dedicated to the challenge of de- viduals with sensitive behavioral immune systems (i.e., fending against pathogens. What may perhaps be less those who are prone to experience disgust) uncon- appreciated is that over the course of evolution, hu- sciously tag immigrants as bearers of pathogens and ex- mans also developed a behavioral immune system at perience strong motivations to avoid them. In building the psychological level that continuously scans for po- this theoretical claim, we incorporate disgust and the tential pathogen threats (e.g., infected food, objects, or behavioral immune system into the standard political people) outside of cognitive awareness and, upon de- science models of emotional processing. These models tection, motivates individuals to take precautions that