Why you should be skeptical of “human nature”: U.S. undergraduates are WEIRD

July 16, 2010

That is, they come from cultures that are Western, educated, industrialized, rich and democratic. And because of that, they might be skewing psychological research that purports to uncover elements of a universal human nature, according to a new (and looong) paper set to appear in Behavioral and Brain Sciences.

Here’s how the authors put it in a brief summary for Nature:

A 2008 survey of the top psychology journals found that 96% of subjects were from 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, rarely adding 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 to ignore. For example, many studies have shown that Ameri-cans, Canadians and western Europeans rely on analytical reasoning strategies — which separate objects from their contexts and rely on rules to explain and predict behaviour — substantially more than non-Westerners. Research also indi-cates that Americans use analytical thinking more than, say, Europeans. By contrast, Asians tend to reason holistically, for example by con-sidering people’s behaviour in terms of their situation1. Yet many long-standing theories of how humans perceive, categorize and remember emphasize the centrality of analytical thought.

It is a similar story with social behaviour related to fairness and equality. Here, research-ers often use one-shot economic experiments such as the ultimatum game, in which a player decides how much of a fixed amount to offer a second player, who can then accept or reject this proposal. If the second player rejects it, neither player gets anything. Participants from industrialized societies tend to divide the money equally, and reject low offers. Peo-ple from non-industrialized societies behave differently, especially in the smallest-scale non-market societies such as foragers in Africa and horticulturalists in South America, where peo-ple are neither inclined to make equal offers nor to punish those who make low offers4.

Here’s the money data, from a write-up in Science:

Some explanation, from the full BBS paper:

The results show substantial differences among populations, with American undergraduates anchoring the extreme end of the distribution, followed by the South African-European sample from Johannesburg. On average, the undergraduates required that line “a” be about a fifth longer than line “b” before the two segments were perceived as equal. At the other end, the San foragers of the Kalahari were unaffected by the so-called illusion (it is not an illusion for them). While the San’s PSE value cannot be distinguished from zero, the American under-graduates’ PSE value is significantly different from all the other societies studied.

As discussed by Segall et al., these findings suggest that visual exposure during ontogeny to factors such as the “carpentered corners” of modern environments may favor certain optical calibrations and visual habits that create and perpetuate this illusion. That is, the visual system ontogenetically adapts to the presence of recurrent features in the local visual environment.

Here’s the Segall et al. paper. The BBS authors point out that the Sander-Parallelogram and the Horizontal-Vertical illusions were also tested and found to vary cross-culturally. Here’s more background.

If this data is interpreted correctly, and it’s not simply the case that (say) people in other societies are understanding the test instructions differently, then that strikes me as pretty powerful. I’m embarrassed to admit that some Ani Difranco lyrics even spring to mind: “Who says I like right angles? These are not my laws, these are not my rules.

If you want a more anthropologically subtle discussion of the paper, check out this post on Neuroanthropology.

Via Savage Minds.

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2 Responses to “Why you should be skeptical of “human nature”: U.S. undergraduates are WEIRD”

  1. Naomi Most Says:

    Hell, even different KINDS of US undergraduates act differently in the ultimatum game. Dan Ariely’s _The Upside of Irrationality_ talks about the vast differences between what economics students do (usually the first people to sign up for these experiments) and what everybody else does.

    I’ll just sum it up quickly: economics students assume that everyone is going to assume selfish behavior from everyone else. So the typically accepted Ultimatum is 19 to 1.

    For just about everybody else in the undergraduate experimentation set, however, the average accepted Ultimatum is 12 to 8.

    Ariely has some pretty funny commentary about what happens when you mix economists with non-economists in these games, too.

  2. JR Minkel Says:

    Nice, thanks for the reference.


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