We examine the effect of self-selected peer information on individual behavior and social norm formation via two experiments (N=1,945; N=2,414) using a lying game and political identification. A self-serving bias emerges in endogenous information search, wherein lenient sources (i.e., sources containing more tolerant empirical or normative information regarding dishonesty), especially those aligned with political identification, are preferred. Selecting lenient sources about peer perception of social norms boosts dishonesty, while peer behavior information chiefly influences expectations about dishonesty, with a minor impact on own behavior. Importantly, peer approval expectations stay largely unaltered by both information types. In a follow-up experiment with exogenously assigned sources, the influence of social information on behavior and expectations is diminished.