A meta-analysis of the effectiveness of implementation intentions for pro-environmental behavior adoption

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Many studies have indicated the difficulties that motivated consumers encounter to effectively carry out their intentions to behave sustainably. Goal planning, such as the formulation of implementation intentions, may be effective in facilitating the performance of sustainable actions. However, because past studies have produced mixed results, we do not know under which conditions goal planning is more effective for sustainable behavior adoption. Drawing from goal planning theories, we propose a comprehensive conceptual framework to explain the plausible moderators of the effectiveness of implementation intentions. We test this framework with a random-effects meta-analysis of the existing evidence (k = 31; N = 10,466) to estimate the overall effect of implementation intentions on the adoption of sustainable behavior. The findings show that implementation intentions have an overall large effect (d = 0.781), and moderate when only experimental studies are considered (d = 0.473). Implementation intentions are more effective for sustainable behaviors that require more effort, time or money and when individuals can adapt their plans to their circumstances. The conclusions of this study are relevant for improving both future research and the application of implementation intentions to scale up sustainable behavior adoption.