Long-term effects of social norm interventions on pro-environmental behaviours: A systematic review and meta-analysis

Anthropogenic climate change poses a serious threat to human health, economic stability, and biodiversity, underscoring the growing importance of interventions that promote pro-environmental behaviour. Previous meta-analyses suggest that social norm interventions, which inform individuals about behavioural norms or societal attitudes towards specific behaviours, are effective in the short-term. However, further research is needed to determine whether effects are sustained over time. Our systematic review and meta-analysis aimed to assess the long-term effectiveness of controlled field experiments employing social norm interventions for pro-environmental behaviours. It included a search from induction to February 4 th , 2025 in Scopus, Web of Science, ERIC, PsycInfo, and OSF Preprints. We included 24 publications reporting on 25 studies in the narrative review, ten of which were incorporated into the quantitative synthesis. The random-effects meta-analysis yielded a small but significant effect ( g =-0.07; 95%CI = -0.11 to -0.03, p =.0022; I 2 =76%) compared to passive control conditions (M follow-up 22.05 months; SD=19.04). Of the 15 studies reviewed narratively, 13 reported reductions in consumption behaviours ranging from -0.081% to 30% and were thus largely consistent with the results of the meta-analysis. Given their their low cost and scalability, even small effects may yield meaningful societal impact. The pooled effect should be interpreted with caution, as the meta-analysis included only ten studies and exhibited substantial heterogeneity among them. Future research should explore strategies to enhance the long-term effectiveness of social norm interventions and potential moderators and mediators. • Social norm interventions provide information regarding behaviours and attitudes of relevant peer groups and can be implemented at large scale at low-cost • Controlled field experiments indicate a small but significant long-term effect of social norm interventions on promoting pro-environmental behaviour • While modest in magnitude, social norm interventions represent an effective strategy to enhance sustained pro-environmental behaviours • Future research should identify moderators and mediators that can enhance the effectiveness of social norm interventions