“…In 1,500 pairs of Swedish and British twins, researchers found that aggressive and nonaggressive antisocial behavior have both environmental and hereditary influences (Eley, Lichenstein, & Stevenson, 1999). Research on the causes of aggression includes work on social learning, imitation, family violence, child abuse, neglect, school aggression, TV violence, malnutrition, structural and functional brain abnormalities, hormones (e.g., testosterone), and neurotransmitters (e.g., serotonin) (Campbell, Woods, Chouaf, & Parker, 2000;Feshbach & Feshbach, 1998;Fishbein, 2001;Huesmann, 1997;Liu, Raine, Venables, & Mednick, in press;Little & Kantor, 2002;Lutenbacher, 2000;Preski & Shelton, 2001;Raine, 2002). This research is slowly beginning to emphasize the more dynamic, intricate, and complex roles played by risk factors in shaping the complex construct of aggression and antisocial behavior in a developmental context (Cicchetti & Lynch, 1993;Susman, 1993).…”