These types of behaviors present themselves differently at different ages, but may continue over time. Children who display disruptive behavior at an early age are the same individuals who display different problem behaviors at a later age. In fact, problem behaviors do not replace each other, but instead are stacked against youngsters, resulting in a cumulative effect. Some behaviors in youngsters are clear risk factors for later delinquency; in boys, the strongest predictors of delinquency are aggression, drug use, and stealing. Patterns of behavior including frequency, variety, multiple settings, and early onset are also precursors to later delinquency. Children displaying hyperactivity, impulsiveness, and attention (HIA) problems in conjunction with conduct problems are at high risk of delinquency. Biological factors, for example exposure to neurotoxic substances, can also lead to deviant behavior. Academic problems such as incomplete education can lead to higher unemployment and contribute to delinquency. Family and peer relationships may also predict later delinquent behaviors. Several developmental paths toward antisocial outcomes have been identified: the aggressive/versatile path, the non-aggressive path, and the exclusive substance-abuse path. There is some evidence of critical periods of malleability and bonding in which children appear to be particularly vulnerable to risk factors. 2 figures and 42 notes (Author abstract modified)