Refining the maturity principle of personality development by examining facets, close others, and comaturation.

Across adulthood, people tend to experience psychologically adaptive personality trait change, a robust finding known as the maturity principle of personality development. We identify three open areas of inquiry regarding personality maturation and address them in a preregistered study, using a sample of U.S. adults ages 30-70 who completed a battery of personality questionnaires and were rated by two close others twice over an 11- to 16-year period ( = 1,785, = 401). First, it is unclear whether the maturity principle applies to narrower facet-level traits, as there has been little research into facet development across adulthood. We examined 47 facet scales and found that most developed adaptively across ages 30-70, but some did not mature, and three healthy facets (activity, openness to feelings, and social potency) declined significantly across adulthood, counter to the maturity principle. Second, no longitudinal research has tested whether personality maturation is perceived similarly by close others. We compared self- and other-rated development and found that close others perceived greater maturation than the self in Agreeableness, Conscientiousness, Neuroticism, and five facets. Finally, few studies have examined whether traits comature in adulthood. We found that correlated change between healthy facets was small in magnitude. Additionally, we found tighter comaturation in other-reported development than self-reported development. We use these results and past research to expand and refine our understanding of personality maturation across adulthood. (PsycInfo Database Record (c) 2022 APA, all rights reserved).