Monitoring items were included in the mother interview conducted in the summer following fifth grade when the participants were aged 11 years. We use monitoring as reported at this age because the reports preceded the assessments of externalizing behavior analyzed here and we were interested in how monitoring may interact with genetic susceptibilities to predict subsequent trajectories of externalizing. Nine items, each rated on a 5-point scale, were combined to create a composite scale.36 These items asked the mother to report how often (1) she thinks her child goes to places he or she is asked not to go to; (2) a parent or other adult is present when the child is at a friend's house; (3) she would know if the child played with children who get in trouble; (4) the child calls, leaves a note, or communicates with her if he or she is going out when at home without an adult; (5) she talks with her child about what he or she does with friends when away from home; and if she knows (6) where the child
