Some personality types thought to cut across cultures may not be as universal as previously thought, according to researchers who spent two years studying an isolated indigenous community in the Bolivian Amazon.

Members of the Tsimane, a society of farmer-foragers that lives in a constellation of villages, did not fit neatly into the "Big Five" dimensions of personality that have been widely recognized by personality researchers.

These five dimensions — through which people reveal their levels of openness, conscientiousness, extraversion, agreeableness and neuroticism — were not expressed in the same ways that researchers have observed in several other cultures.

Instead, the Tsimane recombine personality traits that are typically linked under the Big Five — known in academic circles as the Five-Factor Model — into two other pronounced dimensions: levels of industriousness and levels of socially beneficial behavior, or "prosociality."

"Despite its popularity, there is no good theory that explains why the Big Five takes the form it does, or why it is so commonly observed," said lead author Michael Gurven of the University of California, Santa Barbara.

By way of example, Gurven notes that, among the industrious Tsimane farmers, traits normally associated with conscientiousness — like efficiency, perseverance and thoroughness — were also bundled with being energetic, relaxed and helpful.

Differences in lifestyle and environment, he suggests, may foster personalities that defy categorization under the Big Five.

"In small-scale societies, individuals have fewer choices for social or sexual partners and limited domains of opportunities for cultural success and proficiency," he notes. "This may require abilities that link aspects of different traits."

The study, which was published in a recent issue of the American Psychological Association’s Journal of Personality and Social Psychology, is the first to apply stringent methodological controls to a large group of purely indigenous people.

Previous studies have largely focused on urban populations with high literacy rates -- conditions that were absent for most of human history. The traits expressed by the Tsimane, note the authors, may better reflect societies that are highly social and subsistence-based.

Gurven suggests that much more can be learned about personality types outside Western, industrialized and educated populations.

"Rather than just point out a case study where the Big Five fails, our goal should be to better understand the factors that shape personality more generally."