The concept of personality refers to the profile of stable beliefs, moods, and behaviors that differentiate among children and adults who live in a particular society. The profiles that differentiate children across cultures of different historical times will not be the same because the most adaptive profiles vary with the values of the society and the historical era. For example, an essay on personality development written 300 years ago by a New England Puritan would have listed piety as a major psychological trait; but that would not be regarded as an important personality trait in contemporary America.

Contemporary theorists emphasize personality traits having to do with individualism, internalized conscience, sociability with strangers, the ability to control strong emotion and impulse, and personal achievement.

An important reason for the immaturity of our understanding of personality development is the heavy reliance on questionnaires that are filled out by parents...