The structure of personality refers to the covariation among specific behavioral patterns in a population. Statistically derived models of personality---such as the Big Five or HEXACO models---usually assume that the covariance structure of personality characteristics is a human universal. Cross-cultural studies, however, have challenged this view, finding that less complex societies exhibit stronger covariation among behavioral characteristics, resulting in fewer derived personality factors.

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... explain these results, we propose the niche diversity hypothesis, which predicts that a greater diversity of social and ecological niches elicits a more diverse set of multivariate behavioral profiles, and hence lower trait covariance, at the population level. We formalize this hypothesis as a computational model in which individuals assort into niches, which influence their behavioral traits. We find that the model provides strong support for the niche diversity hypothesis and reproduces empirical results from recent cross-cultural studies. This work provides a general explanation for differences in personality structure between populations in both humans and other animals, and also produces several new empirical predictions. It also suggests a radical reimagining of personality trait research: instead of reifying statistical descriptions of manifest personality structures, research should focus more attention on modeling their underlying causes.