Objective: Personality traits change in both mean levels and variance across the life span but the mechanisms underlying these developmental trends remain unclear. Social Investment Principle (SIP) suggests that social expectations drive personality changes in adulthood. Accordingly, we tested whether differences between personality traits in social expectations for them can explain their different change trajectories in young adulthood.
Methods: A pool of 257 personality items was used to measure personality traits' means and variances (N = 1096), and levels expected by friends, partners and bosses/supervisors (N = 121).
Results: Raters were consistent in their expectations for how young adults should think, feel and behave. Traits under stronger expectations had higher mean levels and lower variances than traits under lower expectations; trait means and variances increased with age, but inconsistently with the SIP, these increases were unrelated to the traits' expected levels.
Conclusion: Our results are only partially consistent with the SIP.
Keywords: mean-level; personality development; social expectations; social investment principle; variance.
© 2023 The Authors. Journal of Personality published by Wiley Periodicals LLC.