Normal adolescent development, which follows its own progressive pattern (preadolescence, early adolescence, adolescence proper, and late adolescence) as described by Blos (1963), is characterized by healthy, productive growth and by development of the ability to plan an effective future. The eventual result is an adult who is a contributing member of society. One of the major theories that pertains to adolescent development focuses on attachment. Because abused children by definition have negative parent-child interactions that might disrupt or interfere with the formation and positive function of attachment, developmental theory concerning attachment is of particular relevance. Assumptions about cognitive ability at different life stages are based on theories of "normal" cognitive development. Piaget's cognitive-developmental theory is the most thorough and integrated theory proposed in this area thus far. Moral development is endangered by children's experience of abuse and neglect, because issues of justice, right and wrong, and fairness are clearly compromised. Other theories of adolescent development discussed pertain to physical development, Freud's theory of psychosexual development, personality development and identity formation, and societal demands and social development.