This paper reports the results from a controlled field experiment designed to investigate the causal effect of unannounced, public recognition on employee performance. We hired more than 300 employees to work on a three-hour data-entry task. In a random sample of work groups, workers unexpectedly received recognition after two hours of work. We find that recognition increases subsequent performance substantially, and particularly so when recognition is exclusively provided to the best performers. Remarkably, workers who did not receive recognition are mainly responsible for this performance increase. Our results are consistent with workers having a preference for conformity and being reciprocal at the same time.JEL Classifications: C93, M52. Keywords: employee motivation, recognition, reciprocity, conformity, field experiment. * We gratefully acknowledge comments and suggestions by a Department Editor, an Associate Editor, three anonymous referees, Iwan Barankay, Gary Charness, Tore Ellingsen, Dirk Engelmann, Guido Friebel, David Gill, Michael Kosfeld, Steve Levitt, John List, Michel Maréchal, Dina Pommeranz, Ingrid Rohde, Marie Claire Villeval, and numerous seminar and conference participants. We thank Ann-Kathrin Koessler for excellent research assistance. The experiment has been conducted within the ethical guidelines of our home institutions.