risky experimentation does not extend beyond adolescence, ceasing as identity becomes settled with maturity. Much adolescent involvement in illegal activity is an extension of the kind of risk taking that is part of the developmental process of identity formation, and most adolescents mature out of these tendencies.

Adolescents differ from adults and children in three important ways that lead to differences in behavior. First, adolescents have less capacity for self-regulation in emotionally charged contexts, relative to adults. Second, adolescents have a heightened sensitivity to proximal external influences, such as peer pressure and immediate incentives, relative to children and adults. Third, adolescents show less ability than adults to make judgments and decisions that require future orientation. The combination of these three cognitive patterns accounts for the tendency of adolescents to prefer and engage in risky behaviors that have a high probability of immediate reward but can have harmful consequences.

Evidence of significant changes in brain structure and function during adolescence strongly suggests that these cognitive tendencies characteristic of adolescents are associated with biological immaturity of the brain and with an imbalance among developing brain systems. This imbalance model implies dual systems: one involved in cognitive and behavioral control and one involved in socioemotional processes. Accordingly, adolescents lack mature capacity for self-regulation because the brain system that influences pleasure-seeking and emotional reactivity develops more rapidly than the brain system that supports self-control.

Adolescent risk taking and delinquent behavior result from the interaction between the normal developmental attributes of adolescents described above and the environmental influences to which they are exposed before and during this stage of development. Put simply, the brain plays an enormous role in determining behavior, but individual development is affected strongly by the interplay between the brain and an adolescent’s environment. In particular, the likelihood and seriousness of offending, as well as the effects of interventions, are strongly affected by the adolescent’s interactions with parents, peers, schools, communities, and other elements of his or her social environment.

THE JUVENILE JUSTICE SYSTEM

The vast majority of youth who are arrested or referred to juvenile court have not committed serious offenses, and half of them appear in the system only once. Regardless of how serious delinquency is defined, the evidence indicates that youth who commit serious offenses constitute a very small proportion of the overall delinquent population and that their



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