  Online games provide a rich recording of interactions that can contribute to
our understanding of human behavior. One potential lesson is to understand what
motivates people to choose their teammates and how their choices leadto
performance. We examine several hypotheses about team formation using a large,
longitudinal dataset from a team-based online gaming environment. Specifically,
we test how positive familiarity, homophily, and competence determine team
formationin Battlefield 4, a popular team-based game in which players choose
one of two competing teams to play on. Our dataset covers over two months of
in-game interactions between over 380,000 players. We show that familiarity is
an important factorin team formation, while homophily is not. Competence
affects team formation in more nuanced ways: players with similarly high
competence team-up repeatedly, but large variations in competence discourage
repeated interactions.
