Social and Cognitive Peer Effects: Experimental Evidence from Selective High Schools in Peru Roman´ Andres´ Zarate´ ∗ November 14, 2018 Job Market Paper Please find the latest version here. Abstract A growing literature emphasizes the importance of social skills in the labor market. However, to date, no study addresses the role of peer characteristics in the formation of social skills. This paper reports estimates of cognitive and social peer effects from a large-scale field experiment at selective boarding schools in Peru. My experimental design overcomes some methodological challenges in the peer effects literature. I ran- domly varied the characteristics of roommates with two treatments: (a) less or more sociable peers (identified by their position in the school’s friendship network before the intervention) and (b) lower- or higher-achieving peers (identified by admission test scores). While more sociable peers enhance the formation of social skills, higher- achieving peers do not improve academic achievement; in fact, they further reduce the academic performance of lower-achieving students. These results appear to be driven by students’ self-confidence. I interpret these findings in the context of a sim- ple self-confidence model where students infer their skills by interacting with their peers. ∗Department of Economics, MIT. Email:
[email protected]. I am deeply grateful to my advisors Joshua Angrist, Esther Duflo, and Parag Pathak for their guidance throughout this project. I also thank Daron Acemoglu, Abhijit Banerjee, and Frank Schilbach for their helpful suggestions. This paper would not have been possible without the support of the staff of the Ministry Education of Peru; I especially thank Mar´ıa Antonieta Alva and Cinthia Wicht for their collaboration and support, and Paola Encalada for her dedicated work at different stages of this project.