Can social interactions be used to favor the consumption of fair-trade products? Social interactions can alter purchase behaviors by triggering either self-image concerns (when one observes others' decisions without being observed) or social-image concerns (when everybody observes everyone). A laboratory experiment is designed to identify separately the role of these motivators, using real auctions for a standard and a fair-trade chocolate, and controlling carefully for taste and package differences. The willingness-to-pay (WTP) for the chocolates and the premium that the subjects grant to the fair-trade variety are analyzed. The results reveal that both social and self-image matter: the subjects give a higher premium to the fairtrade choco...