中文摘要：

借助某高等院校的学生数据，利用多层次模型，证明宿舍同伴、班级同伴的学习能力对于个人学习成绩存在稳定且较强的因果效应。研究发现，在我国，班级群体大于宿舍群体对大学生学习成绩的影响，这种影响几乎接近甚至超过个体学习能力的影响。此外，同伴影响的性别差异显著：宿舍同伴的影响，女生大于男生；班级同伴的影响，男生大于女生。最后，不同能力个体受同伴影响的作用也是不同的：学习能力较高和居中的学生，其成绩受同伴影响显著；学习能力较低的学生，其成绩不受任何同伴影响。

英文摘要：

Capitalizing on rich data from a university in Western China, the author reports the esti- mates from multilevel models to demonstrate the causal effects of peer influence on students~ academic performance. This study obtains the following results. First, classmates are found to have stronger o- verall effects on academic performance than do roommates, and their effects seem also to exceed those of study abilities, as measured by college entrance examination scores. Second, there is a consistent gender difference in peer effects： while roommate effects are greater for females than for males, classmate effects are greater for males than for females. Finally, peer effects vary significantly among students with different academic abilities： peer effects are significant for high- and medium-achievers but not significant for low-achievers.