He model of personality development states that with time and age people become more adept at interacting with their environment in ways that promote increased stability in personality

The cumulative personality  model of personality development states that with time and age people become more adept at interacting with their environment in ways that promote increased stability in personality.
 This model integrates the findings of empirical research on the development of personality traits with the theoretical and empirical models derived from identity research in an attempt to explain the patterns of personality.