Scientists, educators, and parents of teens have long recognized the potency of peer influences on children and youth, but until recently, questions of how and why adolescents emulate their peers were largely overlooked. This book presents a framework for understanding the processes by which peers shape each other's attitudes and behavior, and explores implications for intervention and prevention. Leading authorities share findings on such topics as how drug use, risky sexual behavior, and other deviant behaviors "catch on" among certain peer groups or cliques; the social, cognitive, developmental, and contextual factors that strengthen or weaken the power of peer influence; and the nature of positive peer influences and how to support them. The book includes eleven chapters in four sections. Part I, Introduction, includes: (1) Current Issues in Peer Influence Research (Mitchell J. Prinstein and Kenneth A. Dodge). Part II, Peer Influence Mechanisms, includes: (2) A Comprehensive Conceptualization of the Peer Influence Process in Adolescence (B. Bradford Brown, Jeremy P. Bakken, Suzanne W. Ameringer, and Shelly D. Mahon); (3) Cognitive Social Influence: Moderation, Mediation, Modification, and...the Media, Frederick X. Gibbons, Elizabeth A. Pomery, and Meg Gerrard); (4) Dynamics and Ecology of Adolescent Peer Influence (Thomas J. Dishion, Timothy F. Piehler, and Michael W. Myers); and (5) Deviance Regulation Theory: Applications to Adolescent Social Influence (Hart Blanton and Melissa Burkley). Part III, Altering Peer Influence Effects: Moderators and Interventions, contains: (6) Variation in Patterns of Peer Influence: Considerations of Self and Other (William M. Bukowski, Ana Maria Velasquez, and Mara Brendgen); (7) Adolescent Peer Influences: Beyond the Dark Side (Joseph P. Allen and Jill Antonishak); (8) Mobilizing and Weakening Peer Influence as Mechanisms for Changing Behavior: Implications for Alcohol Intervention Programs (Deborah A. Prentice); and (9) Identity Signaling, Social Influence, and Social Contagion (Jonah Berger). The final section, Part IV, Underexplored Contexts for Potential Peer Influence Effects, includes: (10) Homophily in Adolescent Romantic Relationships (Wyndol Furman and Valerie A. Simon); and (11) Peer Influence in Involuntary Social Groups: Lessons from Research on Bullying (Jaana Juvonen and Adriana Galvan.)