Fig. 2.

The coevolution of friendship and studying ties. Estimates and 95% confidence intervals of key parameters in a stochastic actor-oriented model are shown. Additional controls include network processes (e.g., reciprocity, transitivity, and popularity) and mechanisms that relate to individual variables (e.g., perceived cleverness, homophily, and high-school GPA). Full results are provided in SI Appendix, section 2.2.1; in SI Appendix, Table S8, effects 43a, 39a, 43b, and 39b correspond to estimates 1–4, respectively.