Social investment theory is a psychological theory that claims that changes in personality traits over time are driven by changes in persons' commitments to social roles and institutions.
[1] For instance, young adults may undertake efforts to be "more socially dominant, agreeable, conscientious, and less neurotic"[2] in order to establish their careers or families; in so far as society rewards these efforts, the related personality traits are reinforced.
Since the late 1990s, there has been substantial scientific evidence that personality traits continue to change after childhood, especially during young adulthood.
[3] Generally, personality traits converge towards more agreeableness, conscientiousness, and emotional stability.
This perspective assumes the development of identities through psychological commitments to social institutions in the form of social roles, which offer rewards (and foster expectations of rewards) for displaying "adult" personality traits, which - through reinforcement - promote durable changes in personality traits.