What's Really Human?

The trouble with student guinea pigs.

Where would psychology be without lab rats—by which I mean American undergraduates? These human guinea pigs have spent hours in psych labs staring at optical illusions to reveal how the human visual system is wired. They have taken tests that reveal the need for a positive self-image—“an urge so deeply human,” a psychologist said, “we can hardly imagine its absence”—and that demonstrate the “fundamental attribution error,” in which people explain behavior by temperament (“she’s screaming because she’s an angry person”) rather than situation (her kid just fingerpainted the bedroom wall).

My repeated use of the word “human” above is deliberate. When psychologists discover something in lab experiments, the findings often make their way into journals, textbooks, and popular lore as aspects of human nature: universal and the result of evolution. While some scientists voice skepticism that a discovery about college sophomores applies to, say, Tsimane tribesmen of Amazonia, all too many findings are cast as illuminating The Human Mind.

Now such skepticism is backed up by more than a hunch. Three psychology researchers have done a systematic search of experiments with subjects other than American undergrads, who made up two thirds of the subjects in all U.S. psych studies. From basics such as visual perception to behaviors and beliefs about fairness, cooperation, and the self, U.S. undergrads are totally unrepresentative, Joseph Henrich of the University of British Columbia and colleagues explain in a paper in Behavioral and Brain Sciences. They share responses with subjects from societies that are also Western, educated, industrialized, rich, and democratic (WEIRD), but not with humanity at large.

Scientists have long known that American minds differ from East Asian minds. The latter think more holistically, see context and surroundings more than discrete objects, and subsume the individual to society. But given the difference in culture between the U.S. and East Asia, no one claims the American way is universal.

Many behaviors with no obvious cultural component were supposed to be. Take the optical illusion in which a line segment, A, has an--outward--pointing arrow on each end, and an identical segment, B, has an inward--pointing arrow on each. To most American undergrads, B looks longer by some 20 percent. This has been cast as a general property of human vision. But to the San of the Kalahari, African hunter-gatherers, the lines look (correctly) the same length. The illusion arises when kids grow up in an environment filled with right angles. It is not “human,” but specific to WEIRD cultures.

So are tradeoffs between justice and rationality. The “ultimatum game”—scientists give money to player A, who decides how to split it with player B, but if B rejects the split neither gets anything—is used to probe the sense of fairness. Given $10, American undergrads typically offer $4 or $5 as A, and as B reject anything below $3, preferring to walk away with nothing rather than accept an unfair split. These actions purportedly mean that humans have a highly evolved sense of justice, causing us to make fair offers and punish unfair ones even at our own expense—behavior that supposedly evolved to maintain cohesion in tribal societies and prevent freeloading. But people from small, nonindustrial societies, such as the Hadza foragers of Tanzania, offer about $2.50 to the other player—who accepts it. A “universal” sense of fairness and willingness to punish injustice may instead be a vestige of living in WEIRD, market economies.

As Henrich and his colleagues pored over studies, the list of universals-that-aren’t kept growing. It is not “human nature” to be risk-averse about taking financial chances, as is claimed; the Mapuche of Chile and the Sangu of Tanzania, subsistence farmers, embrace such risks. It is not human nature to work harder and longer at a task about which we are given even a little choice (do algebra or history homework first?); Asians are just as motivated when someone they trust makes the choice for them. Mistakenly attributing behavior to temperament, not situation, is not “human”; East Asians and Russians don’t do it. Even within the U.S., studying people different from the typical WEIRD student can yield strikingly different results. The sex differences in spatial ability found among middle-class kids do not show up among poor ones.

Some “universals” do hold up, such as facial expressions signifying emotions and a taste for sugar. But if psychology hopes to shed light on the human condition, it might do almost as well studying little green men rather than WEIRD undergrads.