Social comparison nudges: What actually happens when we are told what others do?

Social comparison nudges, known to bring about behavioral change, rely on providing information to agents about other agents' decisions or expectations regarding specific actions. Although the procedure consists in transmitting true information, it classically implies a reduction of the transmitted reality: the information provided about others is an average, a proportion, a percentile. What would happen if, instead, full information were shared on what all others do (as nudged agents might legitimately expect), and what would this tell us about how nudges actually work? We assume that cognitive biases occur unintentionally when the information provided is incomplete. By mobilizing Akerlof's (1997) model of social distance, accurately describing polarization effects in social decision-making, we show how the nudge-information conveyed can then act as a decoy: effective in triggering behavioral change, but giving rise to renewed ethical considerations. We illustrate our conjectures with a randomized controlled trial in the context of pesticide use in agriculture in which winegrowers receiving full information about their co-workers' performances are compared with growers receiving the more conventional average performance. After showing that the two differ in their understanding of what others do, we show in the field that the latter nudge induces change unmet by the former.