According to the study, the majority of psychological research is conducted on subjects from Western nations, primarily university students. Between 2003 and 2007, 96 per cent of psychological samples came from countries with only 12 per cent of the world's populations. The U.S. alone provided nearly 70 per cent of these subjects.

However, the study finds significant psychological and behavioral differences between what the researchers call Western, Educated, Industrialized, Rich and Democratic (WEIRD) societies and their non-WEIRD counterparts across a spectrum of key areas, including visual perception, fairness, spatial and moral reasoning, memory and conformity.

The findings, published in Nature July 1 and Behavioral Sciences the week before, raise questions about the practice of drawing universal claims about human psychology and behavior based on research samples from WEIRD societies.

"The foundations of human psychology and behavior have been built almost exclusively on research conducted on subjects from WEIRD societies," says UBC Psychology and Economics Prof. Joe Henrich, who led the study with UBC co-authors Prof. Steven Heine and Prof. Ara Norenzayan. "While students from Western nations are a convenient, low-cost data pool, our findings suggest that they are also among the least representative populations one could find for generalizing about humans."

The study, which reviews the comparative database of research from across the behavioural sciences, finds that subjects from WEIRD societies are more individualistic, analytic, concerned with fairness, existentially anxious and less conforming and attentive to context compared to those from non-WEIRD societies.

According to the study, significant psychological and behavioral differences also exist between population groups within WEIRD nations. For example, U.S. undergraduate students are typically more analytic and choosy and less conforming than U.S. adults without college educations.

"Researchers often implicitly assume that there is little variation across human populations or that these 'standard subjects' are as representative of the species as any other population," says Henrich. "Our study shows there is substantial variability in experimental results across populations. In fact, there is enough evidence that researchers cannot in good faith continue to make species-generalizing claims about Homo sapiens in the absence of comparative evidence."

The research team calls on universities, peer reviewers, funding agencies and journal editors to push researchers to explicitly support any generalizations to the species with evidence or potent inductive arguments. Additionally, they envision the creation of research partnerships with non-WEIRD institutions to further and expand and diversify the empirical base of the behavioral sciences.

An opinion piece by the authors, to appear in the journal Nature on July 1.

Note: If no author is given, the source is cited instead.

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