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BEHAVIORAL AND BRAIN SCIENCES (2010), Page 1 of 75doi:10.1017/S0140525X0999152XThe weirdest people in the world?Joseph HenrichDepartment of Psychology and Department of Economics, University of BritishColumbia, Vancouver V6T 1Z4, .ca/!henrich/home.htmlSteven J. HeineDepartment of Psychology, University of British Columbia, VancouverV6T 1Z4, [email protected] NorenzayanDepartment of Psychology, University of British Columbia, VancouverV6T 1Z4, [email protected]: Behavioral scientists routinely publish broad claims about human psychology and behavior in the world’s top journals basedon samples drawn entirely from Western, Educated, Industrialized, Rich, and Democratic (WEIRD) societies. Researchers – oftenimplicitly – assume that either there is little variation across human populations, or that these “standard subjects” are asrepresentative of the species as any other population. Are these assumptions justified? Here, our review of the comparativedatabase from across the behavioral sciences suggests both that there is substantial variability in experimental results acrosspopulations and that WEIRD subjects are particularly unusual compared with the rest of the species – frequent outliers. Thedomains reviewed include visual perception, fairness, cooperation, spatial reasoning, categorization and inferential induction, moralreasoning, reasoning styles, self-concepts and related motivations, and the heritability of IQ. The findings suggest that members ofWEIRD societies, including young children, are among the least representative populations one could find for generalizing abouthumans. Many of these findings involve domains that are associated with fundamental aspects of psychology, motivation, andbehavior – hence, there are no obvious a priori grounds for claiming that a particular behavioral phenomenon is universal based onsampling from a single subpopulation. Overall, these empirical patterns suggests that we need to be less cavalier in addressingquestions of human nature on the basis of data drawn from this particularly thin, and rather unusual, slice of humanity. We closeby proposing ways to structurally re-organize the behavioral sciences to best tackle these challenges.Keywords: behavioral economics; cross-cultural research; cultural psychology; culture; evolutionary psychology; experiments; externalvalidity; generalizability; human universals; population variability1. IntroductionIn the tropical forests of New Guinea, the Etoro believethat for a boy to achieve manhood he must ingest thesemen of his elders. This is accomplished through ritualized rites of passage that require young male initiates tofellate a senior member (Herdt 1984/1993; Kelley 1980).In contrast, the nearby Kaluli maintain that male initiationis only properly done by ritually delivering the sementhrough the initiate’s anus, not his mouth. The Etororevile these Kaluli practices, finding them disgusting. Tobecome a man in these societies, and eventually take awife, every boy undergoes these initiations. Such boy-inseminating practices, which are enmeshed in rich systems ofmeaning and imbued with local cultural values, were notuncommon among the traditional societies of Melanesiaand Aboriginal Australia (Herdt 1984/1993), as well asin Ancient Greece and Tokugawa Japan.Such in-depth studies of seemingly “exotic” societies,historically the province of anthropology, are crucial forunderstanding human behavioral and psychological variation. However, this target article is not about thesepeoples. It is about a truly unusual group: people from# Cambridge University Press 20100140-525X/10 40.00Western, Educated, Industrialized, Rich, and Democratic(WEIRD)1 societies. In particular, it is about the Western,and more specifically American, undergraduates who formthe bulk of the database in the experimental branches ofpsychology, cognitive science, and economics, as well asallied fields (hereafter collectively labeled the “behavioralsciences”). Given that scientific knowledge about humanpsychology is largely based on findings from this subpopulation, we ask just how representative are these typicalsubjects in light of the available comparative database.How justified are researchers in assuming a species-levelgenerality for their findings? Here, we review the evidenceregarding how WEIRD people compare with otherpopulations.We pursued this question by constructing an empiricalreview of studies involving large-scale comparative experimentation on important psychological or behavioralvariables. Although such larger-scale studies are highlyinformative, they are rather rare, especially when compared to the frequency of species-generalizing claims.When such comparative projects were absent, we reliedon large assemblies of studies comparing two or threepopulations, and, when available, on meta-analyses.1

Henrich et al.: The weirdest people in the world?Of course, researchers do not implicitly assume psychological or motivational universality with everything theystudy. The present review does not address those phenomena assessed by individual difference measures for whichthe guiding assumption is variability among populations.Phenomena such as personal values, emotional expressiveness, and personality traits are expected a priori to varyacross individuals, and by extension, societies. Indeed,the goal of much research on these topics is to identifythe ways that people and societies differ from oneanother. For example, a number of large projects havesought to map out the world on dimensions such asvalues (Hofstede 2001; Inglehart et al. 1998; Schwartz &Bilsky 1990), personality traits (e.g., McCrae et al. 2005;Schmitt et al. 2007), and levels of happiness, (e.g.,Diener et al. 1995). Similarly, we avoid the vast psychopathology literature, which finds much evidence for bothvariability and universality in psychological pathologies(Kleinman 1988; Tseng 2001), because this work focuseson individual-level (and unusual) variations in psychological functioning. Instead, we restrict our exploration toJOSEPH HENRICH holds the Canada Research Chair inCulture, Cognition, and Evolution at the University ofBritish Columbia, where he is appointed Professor inboth Economics and Psychology. His theoretical workfocuses on how natural selection has shaped humanlearning and how this in turn influences cultural evolution, and culture-gene coevolution. Methodologically,his research synthesizes experimental and analyticaltools drawn from behavioural economics and psychology with in-depth quantitative ethnography, and hehas performed long-term fieldwork in the PeruvianAmazon, rural Chile, and in Fiji. Trained in anthropology, Dr. Henrich’s work has been published in the topjournals in biology, anthropology, and economics. In2004 he was awarded the Presidential Early CareerAward, the highest award bestowed by the UnitedStates upon scientists early in their careers. In 2007he co-authored Why Humans Cooperate. In 2009 theHuman Behavior and Evolution Society awarded himtheir Early Career Award for Distinguished ScientificContributions.ARA NORENZAYAN is an Associate Professor of Psychology at the University of British Columbia, Vancouver.He received his Ph.D. from the University of Michiganin 1999, was a postdoctoral fellow at the EcolePolytechnique, Paris, and served on the faculty of theUniversity of Illinois, Urbana-Champaign before hisappointment at UBC. His most recent work addressesthe evolution of religious beliefs and behaviors.STEVEN J. HEINE is Professor of Psychology and Distinguished University Scholar at the University ofBritish Columbia. Much of his work has focused onhow culture shapes people’s self-concepts, particularlytheir motivations for self-esteem. Dr. Heine hasreceived the Early Career Award from the International Society of Self and Identity and the Distinguished Scientist Early Career Award for SocialPsychology from the American Psychological Association. He is the author of a textbook entitled CulturalPsychology, published in 2008.2BEHAVIORAL AND BRAIN SCIENCES (2010) 33:2/3those domains which have largely been assumed, at leastuntil recently, to be de facto psychological universals.Finally, we also do not address societal-level behavioraluniversals, or claims thereof, related to phenomena suchas dancing, fire making, cooking, kinship systems, bodyadornment, play, trade, and grammar, for two reasons.First, at this surface level alone, such phenomena do notmake specific claims about universal underlying psychological or motivational processes. Second, systematic,quantitative, comparative data based on individual-levelmeasures are typically lacking for these domains.Our examination of the representativeness of WEIRDsubjects is necessarily restricted to the rather limited database currently available. We have organized our presentation into a series of telescoping contrasts showing, ateach level of contrast, how WEIRD people measure uprelative to the available reference populations. Our firstcontrast compares people from modern industrializedsocieties with those from small-scale societies. Oursecond telescoping stage contrasts people from Westernsocieties with those from non-Western industrializedsocieties. Next, we contrast Americans with people fromother Western societies. Finally, we contrast universityeducated Americans with non – university-educated Americans, or university students with non-student adults,depending on the available data. At each level wediscuss behavioral and psychological phenomena forwhich there are available comparative data, and weassess how WEIRD people compare with other samples.We emphasize that our presentation of telescoping contrasts is only a rhetorical approach guided by the nature ofthe available data. It should not be taken as capturing anyunidimensional continuum, or suggesting any single theoretical explanation for the variation. Throughout this articlewe take no position regarding the substantive origins of theobserved differences between populations. While many ofthe differences are probably cultural in nature in that theywere socially transmitted (Boyd & Richerson 1985;Nisbett et al. 2001), other differences are likely environmental and represent some form of non-cultural phenotypic plasticity, which may be developmental or facultative,as well as either adaptive or maladaptive (Gangestad et al.2006; Tooby & Cosmides 1992). Other population differences could arise from genetic variation, as observed forlactose processing (Beja-Pereira et al. 2003). Regardlessof the reasons underlying these population differences,our concern is whether researchers can reasonably generalize from WEIRD samples to humanity at large.Many radical versions of interpretivism and culturalrelativity deny any shared commonalities in human psychologies across populations (e.g., Gergen 1973; see critique and discussion in Slingerland 2008, Ch. 2). To thecontrary, we expect humans from all societies to share,and probably share substantially, basic aspects of cognition, motivation, and behavior. As researchers who seegreat value in applying evolutionary thinking to psychologyand behavior, we have little doubt that if a full accountingwere taken across all domains among peoples past andpresent, the number of similarities would indeed belarge, as much ethnographic work suggests (e.g., Brown1991) – ultimately, of course, this is an empirical question.Thus, our thesis is not that humans share few basic psychological properties or processes; rather, we question ourcurrent ability to distinguish these reliably developing

Henrich et al.: The weirdest people in the world?aspects of human psychology from more developmentally,culturally, or environmentally contingent aspects ofour psychology given the disproportionate reliance onWEIRD subjects. Our aim here, then, is to inspireefforts to place knowledge of such universal features ofpsychology on a firmer footing by empirically addressing,rather than a priori dismissing or ignoring, questions ofpopulation variability.2. BackgroundBefore commencing with our telescoping contrasts, wefirst discuss two observations regarding the existing literature: (1) The database in the behavioral sciences is drawnfrom an extremely narrow slice of human diversity; and (2)behavioral scientists routinely assume, at least implicitly,that their findings from this narrow slice generalize tothe species.2.1. The behavioral sciences database is narrowWho are the people studied in behavioral scienceresearch? A recent analysis of the top journals in six subdisciplines of psychology from 2003 to 2007 revealedthat 68% of subjects came from the United States, anda full 96% of subjects were from Western industrialized countries, specifically those in North America andEurope, as well as Australia and Israel (Arnett 2008).The make-up of these samples appears to largely reflectthe country of residence of the authors, as 73% of firstauthors were at American universities, and 99% were atuniversities in Western countries. This means that 96%of psychological samples come from countries with only12% of the world’s population.Even within the West, however, the typical samplingmethod for experimental studies is far from representative. In the Journal of Personality and Social Psychology,the premier journal in social psychology – the subdiscipline of psychology that should (arguably) be the mostattentive to questions about the subjects’ backgrounds –67% of the American samples (and 80% of the samplesfrom other countries) were composed solely of undergraduates in psychology courses (Arnett 2008). In otherwords, a randomly selected American undergraduate ismore than 4,000 times more likely to be a research participant than is a randomly selected person from outside ofthe West. Furthermore, this tendency to rely on undergraduate samples has not decreased over time (Peterson2001; Wintre et al. 2001). Su