How do peers influence the impact of incentives? Despite much work on incentives, little is known about the spillover … effects of incentives. We investigate two mechanisms by which these effects can occur: through peers' actions and peers …' incentives. In a field experiment on snack choice (grapes versus cookies), we randomize who receives incentives, the fraction of …

of any effects six months later. Our results show that incentives can work, at least temporarily, to increase healthy …