Social comparison feedback in decision-making context: Environmental externality levels and psychological traits matter

Social comparison feedback has been widely applied to encourage energy and water conservation, with the ultimate aim to protect ecosystems and the environment. Yet, the effectiveness of social comparison feedback varies. In this study, with 360 UK participants from Prolific, we conducted an online experiment based on a modified dictator game with multi-round purchasing decisions involving trade-offs between individual monetary payoff and real-world carbon offsets donation. A 2 x 3 between-subjects design was implemented, varying in the externality levels associated with the purchase (high versus low), and the type of feedback (self-feedback, social comparison feedback, and tangible emissions feedback - i.e. social comparison enriched with information relating environmental impacts to daily activity and nature). Furthermore, we measured several psychological traits of participants. Our findings show that social comparison interventions are only effective under certain circumstances. Both interventions with social comparison are more effective in the low-externality context. Furthermore, the effect of tangible emissions feedback is moderated by individuals' tendency to conform to specific social norms and compete with others. Compared to standard social comparison feedback, social comparison feedback enriched with tangible emissions information is overall more effective. We highlight the importance of tailoring social comparison interventions to local environmental and cultural contexts.