Social selection and influence account for little of the total phenotypic variation in SELF and PEER. “New” unique environmental factors become relevant at each successive age range, and the impact of earlier non-shared environmental factors is continued via forward transmission. The low parameter estimates for the social influence paths mean that little of the total phenotypic variance in SELF1–4 originates from E5-E8 (see Figure 2C); similarly, little of the total variance in PEER1–4 originates from E1–E4. Still, these causal influences could not be removed from the model. The fact that social selection paths could be constrained to be equal over time suggests that one’s influence on one’s E-related affiliation with peers is not highly variable, even though one’s peer group might change. In contrast, we could not constrain the social influence paths to be equal, indicating that the extent to which peers’ drinking influences one’s own drinking varies from adolescence into adulthood.
