Abstract
Behavior genetic research has revealed that many "environmental" variables are partially influenced by genetic factors. Known as gene-environment correlation (rGE), this line of scholarship provides insight on how and why individuals select into certain environments. Juxtaposing this body of evidence with research on peer group homophily-the tendency for peers to resemble one another on certain traits such as academic ability-raised two research hypotheses: (1) youth will associate with peers who receive grades similar to themselves (i.e., homophily for GPA); and (2) a portion of the variance in peer group GPA (i.e., the peer network average GPA) will be explained by individuals' genetic self-selection into the peer group (rGE). The results supported both hypotheses by showing a strong predictive relationship between the target individual's GPA and that of his/her peers and by revealing that 72% of the variance in peer group GPA was explained by genetic influences. (C) 2014 Elsevier B.V. All rights reserved.