We study how the random assignment of new students to introductory-week groups shapes subsequent friendship networks. Both women and men report being much more likely to be friends with same-gender students with whom they were (randomly) assigned in a group during their first week on campus, and the effect is much stronger for women. When students from the same cohort play a repeated trust game in the experimental laboratory, their behavior helps explain what we observed in the field. Women display more stability and less flexibility than men in their interactions with individuals with whom they had previously played. This difference is enough to generate homophily in the observational data even though subjects show no intrinsic preference for same-gender interaction.

我们研究了将新生随机安排到介绍周小组的方式如何影响随后的友谊网络。男性和女性都报告说，在校园的第一周里与他们（随机）被分配给同性别的学生成为朋友的可能性更大，而对女性的影响要大得多。当来自同一队列的学生在实验实验室玩重复的信任游戏时，他们的行为有助于解释我们在实地观察到的情况。在与以前玩过的人的互动中，女性比男性表现出更多的稳定性和灵活性。即使对象没有表现出对相同性别互动的内在偏好，这种差异也足以在观测数据中产生同质性。