Pre-print, Working paper: Can social interactions be used to encourage the consumption of fair-trade products? Social interactions may alter purchase behavior by triggering either self-image concerns (when one sees others' decisions without being seen) or social-image concerns (when everybody sees everyone else). A laboratory experiment is designed to identify separately these concerns, using real auctions for normal and fair-trade chocolate, controlling for taste and packaging differences. The analysis of the willingness-to-pay (WTP) for both types of chocolate reveals that both social- and self-image matter: subjects pay a higher premium for fair-trade chocolate when their decisions are made public. This premium is sensitive to information received about the premia paid by other subjects, even when decisions are private. The higher premium in public auctions results from a lower WTP for normal chocolate, rather than a higher WTP for fair-trade chocolate. Subjects are also much more sensitive to information about others' choices that relaxes the moral or social norm constraining their own choice. We thus conclude that social interactions cannot be used to nudge consumers into fair-trade consumption, at least for ordinary products such as chocolate.