Personality trait development from age 12 to age 18: longitudinal, cross-sectional, and cross-cultural analyses.

Three studies were conducted to assess mean level changes in personality traits during adolescence. Versions of the Revised NEO Personality Inventory (P. T. Costa, Jr., & R. R. McCrae, 1992a) were used to assess the 5 major personality factors. A 4-year longitudinal study of intellectually gifted students (N = 230) was supplemented by cross-sectional studies of nonselected American (N = 1,959) and Flemish (N = 789) adolescents. Personality factors were reasonably invariant across ages, although rank-order stability of individual differences was low. Neuroticism appeared to increase in girls, and Openness to Experience increased in both boys and girls; mean levels of Extraversion, Agreeableness, and Conscientiousness were stable. Results extend knowledge of the developmental curve of personality traits backward from adulthood and help bridge the gap with child temperament studies.