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Vol 466|1 July 2010

OPINION Most people are not WEIRD
To understand human psychology, behavioural scientists must stop doing most of their experiments on Westerners, argue Joseph Henrich, StevenJ. Heine and Ara Norenzayan.
uch research on human behaviour and psychology assumes that everyone shares most fundamental cognitive and affective processes, and that findings from one populationapply across the board. A growing body of evidence suggests that this is not the case. Experimental findings from several disciplines indicate considerable variation among human populations in diversedomains, such as visual perception, analytic reasoning, fairness, cooperation, memory and the heritability of IQ1,2. This is in line with what anthropologists have long suggested: that people fromWestern, educated, industrialized, rich and democratic (WEIRD) societies — and particularly American undergraduates — are some of the most psychologically unusual people on Earth1. So the fact that the vastmajority of studies use WEIRD participants presents a challenge to the understanding of human psychology and behaviour. A 2008 survey of the top psychology journals found that 96% of subjects werefrom Western industrialized countries — which house just 12% of the world’s population3. Strange, then, that research articles routinely assume that their results are broadly representative, rarelyadding even a cautionary footnote on how far their findings can be generalized. The evidence that basic cognitive and motivational processes vary across populations has become increasingly difficult toignore. For example, many studies have shown that Americans, Canadians and western Europeans rely on analytical reasoning strategies — which separate objects from their contexts and rely on rules toexplain and predict behaviour — substantially more than non-Westerners. Research also indicates that Americans use analytical thinking more than, say, Europeans. By contrast, Asians tend to reason...