Self-efficacy boosts triple the effectiveness of pro-environmental recycling interventions: evidence from meta-analytic synthesis

Self-efficacy, individuals' belief in their ability to perform behaviors and achieve outcomes, is a key cognitive determinant of pro-environmental behavior (PEB). While a causal link between a determinant and a behavior is necessary, it is insufficient for informing effective policy design. Evidence-based policy requires answers to two additional questions: first, which interventions can effectively target the chosen determinant in practice, and second, what is their potential impact on the target PEB. However, evidence on the effectiveness of targeting specific determinants like self-efficacy remains scarce. While randomized controlled trials provide the most rigorous evidence, it is rarely available in many policy-relevant contexts. Moreover, general meta-analyses also typically do not pool evidence by determinants. To address this gap, we demonstrate how standard meta-analytic methods can be applied in a novel way to answer the identified policy-relevant questions. Specifically, we deploy this method to assess the effectiveness of including self-efficacy targeting elements (self-efficacy boosts) into household recycling intervention strategies. We find that interventions incorporating self-efficacy boosts are, on average, three times more effective than those without them. In contrast, interventions lacking self-efficacy boosts exhibit minimal or statistically insignificant effects. These results hold across all intervention types, including the commonly used category of norm-based interventions. We also provide practical guidance for implementing self-efficacy boosts based on the analyzed evidence. While our analysis focuses on household recycling, the proposed meta-analytic approach can be applied to inform evidence-based policy across diverse determinants and PEB contexts.