  Understanding how student peers influence learning outcomes is crucial for
effective education management in complex social systems. The complexities of
peer selection and evolving peer relationships, however, pose challenges for
identifying peer effects using static observational data. Here we use both
null-model and regression approaches to examine peer effects using longitudinal
data from 5,272 undergraduates, where roommate assignments are plausibly random
upon enrollment and roommate relationships persist until graduation.
Specifically, we construct a roommate null model by randomly shuffling students
among dorm rooms and introduce an assimilation metric to quantify similarities
in roommate academic performance. We find significantly larger assimilation in
actual data than in the roommate null model, suggesting roommate peer effects,
whereby roommates have more similar performance than expected by chance alone.
Moreover, assimilation exhibits an overall increasing trend over time,
suggesting that peer effects become stronger the longer roommates live
together. Our regression analysis further reveals the moderating role of peer
heterogeneity. In particular, when roommates perform similarly, the positive
relationship between a student's future performance and their roommates'
average prior performance is more pronounced, and their ordinal rank in the
dorm room has an independent effect. Our findings contribute to understanding
the role of college roommates in influencing student academic performance.
