12 Friendship Across the Life Span
examining the characteristics of a child’s friend. Given that friends tend to become
more similar to each other over time, forming a close friendship with a peer who has
negative characteristics (e.g., delinquent behavior, depressive symptoms) could put
that child at risk of developing those same problems.
Deviancy Training
The so- called dark side of friendship was first investigated within groups of delin-
quent boys. Not only do delinquent boys tend to choose friends who are similarly
delinquent (Boivin & Vitaro, 1995), but also these dyads develop even more prob-
lematic behaviors over time (Dishion et al., 1996), suggesting the presence of both
selection and socialization effects. In observing the conversations of delinquent
adolescent friend dyads, Dishion and colleagues (1996) noticed that these boys
tended to respond positively when their friend discussed delinquent activities (e.g.,
by laughing), and this positive response was followed by even more rule- breaking
talk between the boys, a process they termed deviancy training. Importantly, the
more boys engaged in deviant talk, the more likely they were to show an increase
in delinquent offenses two years later, even after controlling for their initial levels
of delinquent behavior. In contrast, boys whose friends responded less positively
to such talk did not show comparable increases. Deviancy training has also been
found to predict increases in tobacco, alcohol, and marijuana use (Dishion, Capaldi,
Spraklen, & Li, 1995), as well as risky sexual behavior and number of police arrests
(Patterson, Dishion, & Yoerger, 2000). Although boys tend to show higher levels of
antisocial behavior and participate in more peer deviancy training than girls, girls
who do engage in deviancy training experience similar increases in antisocial behav-
ior (Snyder, Schrepferman, Bullard, McEachern, & Patterson, 2012).
This process has significant implications for developmental pathways across
childhood and beyond. Deviancy training has been observed even in young chil-
dren. Among kindergarten students, befriending deviant peers and engaging in
deviant talk predicted increases in conduct problems through first grade (Snyder
et al., 2005). Thus, deviancy training may be a marker for the development of early-
onset conduct problems. Because childhood- onset conduct disorder tends to be
associated with longer- lasting antisocial behavior over time than adolescent- onset
conduct disorder (Moffitt, 1993), recognizing such a marker could be beneficial for
identifying children who are most in need of monitoring and intervention.
Depression Contagion
Just as friends of delinquent adolescents tend to be similarly delinquent, friends of
depressed adolescents tend to experience similar levels of depression. As the result
of a socialization process called depression contagion, adolescents whose friends
have initially higher levels of depressive symptoms experience an increase in their