Accompanying the emergence of new representational capacities and self-awareness in the second year is another crowning achievement: the child becomes a moral being. What accounts for the early emergence of morality and children's expanding appreciation of standards of conduct with age? According to sociobiology, morality is grounded in our genetic heritage through prewired emotional reactions. Although psychoanalytic and social learning theories offer different accounts of moral development, both emphasize internalization-the adoption of preexisting standards of behavior as one's own.

Contrary to predictions from Freudian theory, emphasizing power assertion or love withdrawal does not promote conscience formation. Instead, induction, against a backdrop of nurturance, is far more effective. Social learning theorists have shown that modeling combined with reinforcement is effective in encouraging prosocial acts. In contrast, harsh punishment promotes only temporary compliance, not lasting changes in children's behavior.

The cognitive-developmental perspective regards construction-actively attending to and weighing multiple aspects of situations in which social conflicts arise and deriving new moral insights-as central to moral development. Piaget's work was the original inspiration for this perspective.

Kohlberg offers a three-level, six-stage theory of how morality changes from concrete, externally oriented reasoning to more abstract, principled justifications for moral choices. Moral reasoning is influenced by environmental factors such as peer interaction, child-rearing practices, schooling, and aspects of culture. The emergence of self-control is supported by self-awareness and representational and memory capacities.

Aggression, which first appears in late infancy, takes the form of either instrumental or hostile aggression. Whereas boys tend to express overt aggression, girls display more relational aggression. The incidence of delinquent acts rises in the teenage years, but few adolescents become recurrent offenders. Conduct problems that began in childhood are far more likely to persist than are those that first appear in adolescence. Although impulsive, overactive children are at risk for high aggression, whether they become so depends on child-rearing conditions. Among interventions designed to reduce aggression, procedures based on social learning theory and on social-cognitive theory are beneficial.