Imagine a world populated by college undergraduates. A world filled with binge drinkers and sleep-deprived procrastinators tweeting their sexual exploits to virtual friends across the globe. In most psychology studies, these are exactly the people from whom psychology researchers extrapolate fundamental truths about human nature.

Although North American college undergraduates make up only about 0.2 percent of the world's population, they account for a massively disproportionate number of psychology research subjects. In 2008, psychologist Jeffrey Arnett reported that in major social and personality journals, 67 to 80 percent of samples are comprised of college undergraduates. In fact, a college student in this country is 4,000 times as likely to be a psychology research subject than almost anyone else in the world.

University of British Columbia psychologists Joseph Henrich, Steven Heine, and Ara Norenzayan note that psychology studies are by and large conducted on a WEIRD (Western, Educated, Industrialized, Rich, and Democratic) bunch. These WEIRD studies create an odd problem: psychologists often tout their results as generalizable truths about human brains, beliefs, and behaviors. But if the samples aren't representative of the rest of the world, then just how representative are the results?

Henrich and his colleagues suggest, for example, that American study volunteers are more fiercely individualistic than others. They highlight one example of this…