The dynamics of personality and identity in adolescence

The current dissertation focused on adolescent identity formation and personality development. We focused on how these aspects of individuality develop through adolescence, and how individual differences in (the development of) personality and identity relate to problem behavior. For that purpose, we applied: a) variable-centered approaches focusing on how particular traits or dimensions change on average in a group of individuals, and whether individual differences in traits or dimensions are stable or fluctuate across time; and b) person-centered approaches focusing on how a configuration of traits is organized within an individual. Data were used from three longitudinal projects: CONAMORE, RADAR, and L-TIDES. In addition, data from a cross-sectional project involving juvenile delinquents and clinically referred youth was used. Participants in these projects filled out questionnaires on personality, identity formation, conflicts with parents, friendship quality, academic adjustment, and problem behavior. Variable-centered to personality revealed that adolescent’s personalities matured, as they became more agreeable, extraverted, and open to experience when they grew older. In addition, inter-individual differences became more set, and traits became more consistently organized within individuals. For all aspects of development, girls were ahead on boys. Development of personality traits was strongly interrelated with development of problem behavior symptoms, as specific personality characteristics seemed to put adolescents at risk for developing problem behavior symptoms, but problem behavior symptoms also seemed to affect adolescent personality traits. Person-centered approaches to personality revealed that three classic personality types (Resilients, Undercontrollers, and Overcontrollers) were replicable as trajectories of personality development. With another person-centered approach to personality, we showed that it is not the stability of a profile that is linked to psychological adjustment, but the degree to which an individual’s personality profile matches the profile of the average person within a sample. From a developmental perspective, an individual’s personality profile can diverge from the profile of the average person in two ways: one can either be ahead (i.e., hypermaturity) or lag behind (i.e., immaturity) in development. We showed that hypermaturity is related to internalizing problems in boys and girls. Immaturity is related to externalizing problems, but only in girls. With regard to identity formation, early adolescents became increasingly more certain about their current commitments as they exhibited decreases in reconsideration. Middle and late adolescents were involved in identity evaluation, as they exhibited increases in in-depth exploration. As with personality development, girls also seemed to be ahead on boys in identity formation. By tracking early adolescents with daily internet assessments, we demonstrated that identity formation is guided by a certainty-uncertainty (commitment-reconsideration) dynamic that operates on day-to-day level. Moreover, fluctuations in reconsideration predicted a weaker sense of identity in general. Finally, we demonstrated that identity formation is more strongly related to severe forms of delinquency than to other types of severe problem behavior, as juvenile delinquents displayed much more problems with identity formation than clinically referred youth did. In sum, we demonstrated important development changes in personality and identity. Individual differences in (changes in) personality and identity were found to be strongly related to problem behavior