The strength of the work ties

College students often have to team up for class projects, and they select each other based not only on past performance (e.g., grades) but also on whether they have friendship ties (e.g., whether they trust each other). There has not been any study on the relationship between team formation for class projects and social media. To fix that, we ask two group of university students to tell us with whom they wish to work. Afterward, we gathered their online Facebook data and tested the predictors of team formation. We found that self-organized selection of team members does not strongly depend on past grades, but rather on Facebook-derived proxies for tie strength, popularity, extroversion and homophily. These results have important theoretical implications for the team formation literature and practical implications for online educational platforms. © 2016 Elsevier Inc. All rights reserved.