This study examines whether reciprocity is affected by what others know and do. Two types of social effects are investigated within the framework of a modified investment game. On the one hand, we assess the role played by the awareness that own choices are observed by another trustee—i.e., peer pressure. On the other hand, we measure the interaction between trustees’ choices—i.e., social spillovers. We find that peer pressure fosters reciprocity and, to a lesser extent, so do social spillovers.

A large share of our food comes from international supply food chains that are difficult to trace. Therefore, consumers are not aware of their environmental and social effects. We analysed the tomato supply system for Germany. Tomatoes consumed in Germany are produced either in The Netherlands by Polish workers and using large amounts of energy, or in Spain by West African workers and depleting the aquifer. The analysis shows the long-distance effects of food consumption that should be considered when designing strategies for a sustainable global food system. Comparable results can be expected for other food products traded around the world.