Direct and spillover effects of social norm nudges for household recycling: A longitudinal field experiment

Applying social norm nudges to motivate household recycling is becoming increasingly popular. However, little is known about the compatibility between norm-based recycling policies and other waste management measures. Using a longitudinal field experiment with residents in Quzhou, China, we evaluated social norms messaging about household recycling in terms of its impact on recycling behavior and public support for waste prevention and harmless disposal policies. We also assessed treatment effect heterogeneity across subpopulations and persistence after messaging ended. The nudge increased recycling participation and policy support over a five-month treatment period, indicating positive direct and spillover effects. Both effects were more salient among recipients with weaker pro-environmental intrinsic motivation or community social embeddedness; however, they faded over a following five-month period when messaging was removed. Overall, the results suggest that social norm nudges improve the target behavior and facilitate policy synergy, although these benefits are neither universal nor sustainable.