Few psychology theories have as much support as the "Big Five" personality traits — the finding that people's personalities can be described by variations across five basic dimensions: openness to new experience, conscientiousness, extroversion/introversion, agreeableness and neuroticism. But new research with a small South American tribe has thrown the universality of the five factor model into question.

According to a study published Dec. 17 in the Journal of Personality and Social Psychology, a team of researchers administered a translated version of a Big Five personality inventory to 632 Tsimane, members of a small tribe of hunter-gatherers in the Bolivian lowlands. The researchers asked them to rate on a 1-to-5 scale how much words like "aloof," "reserved" and "energetic" described their personalities.

When researchers analyzed the results, they found that the traits did not cluster into the usual Big Five groups. For instance, a person who rated himself as "reserved" also tended to say he was "talkative" — suggesting that the overarching concept of extraversion doesn't hold up in this culture, says lead author Michael Gurven, PhD, an anthropology professor at the University of California, Santa Barbara. In fact, only two clusters of correlated responses emerged from a factor analysis of the 40-item test: industriousness and a tendency to be prosocial.

"Neither of these two factors mapped onto the Big Five," says Gurven.

The Tsimane may have only two factors because there are only so many ways to be successful in that environment — hunting and gathering or being a shaman, leader or sociable charmer capable of convincing friends to share their food, he says.

The finding is surprising given past research led by five factor theorist Robert McCrae, PhD, who found evidence supporting the five factor personality model in more than 50 countries (Journal of Personality and Social Psychology, 2005). Perhaps the five factors failed to emerge in the Tsimane sample due to translation issues or the abstract nature of the questions, he says.

Still, it's an important finding and could shed light on the evolution of personality, McCrae adds. "This is an admirable study, with potentially important theoretical implications," he says.

—Sadie Dingfelder