“Friendship and Delinquency in Early Adolescence: A study of selection and influence effects.”
By Andrea Knecht, Chris Baerveldt, Tom A.B. Snijders, Christian Steglich, and Werner Raub, 2010.
Social Development 19, 494-514.

Similarity in relevant characteristics is a widespread pattern among adolescent friends. This similarity could be caused by different processes. It may be caused by selection of similar others as friends and deselection of dissimilar ones, but also by influence processes where friends adjust their behavior to each other. Both processes have been put forward by criminologists. Social control theory argues that adolescents select each other as friends based on delinquent behavior. Differential association theory, on the other hand, argues that adolescent friends may influence each other's delinquency levels.

Methodological issues have impeded progress on deciding which of these processes leads to similarity among adolescent friends. Until recently, existing statistical methods did not allow for analyzing selection and influence simultaneously. We employ new statistical methods for assessing the empirical evidence for either process, controlling for the other process. These methods are based on "actor-oriented" stochastic simulation models, tracing the process of influence and selection in a social network, and thus enabling us to empirically disentangle selection and influence processes in longitudinal data. The statistical model, as defined for a single classroom, can be regarded as a stochastic simulation model representing the observed differences in friendship relations and delinquency at consecutive observation points as the net result of many small changes occurring continuously between the observations.

Our data are obtained from longitudinal network designs. We analyze data of 544 students in 21 first-grade classrooms of Dutch secondary schools. Information on friendships to classmates and delinquency was gathered at four observation points within one school year. Results indicate that students with a higher level of delinquency have a greater tendency to select delinquent peers as friends and vice versa. We find no evidence that students adjust their own behavior in accordance with the average behavior of their friends. The results are consistent with social control theory but provide no support for differential association theory.

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