Prompting change: A systematic review and meta-analysis of the (un)confounded effects of prompts on pro-environmental behavior

Beyond political action, fostering individuals' pro-environmental behavior (PEB) is imperative to address environmental crises, such as climate change. Prompts are visual and/or verbal reminders to perform certain PEBs. Meta-analytic results by Osbaldiston and Schott (2012) suggest that prompts can increase PEB. However, in many of the included primary studies in this meta-analysis, prompts were confounded with other interventions (e.g., information campaigns). To study whether and under which conditions prompts have an unconfounded effect on PEB, we conducted a pre-registered systematic review following the PRISMA guidelines (N = 61 studies, k = 114 effect sizes). Additionally, we conducted a z-curve analysis to assess the expected replicability of the observed significant findings and ran meta-analyses to calculate the combined effect of (un)confounded prompt interventions on PEB. We find that prompts are effective in promoting PEB (b = 0.67, p < .001), even when no other interventions are implemented simultaneously (b = 0.66, p < .001). The rate of significant results that could be replicated under the same conditions as estimated by z-curve analysis is high (88% - 95% for unconfounded significant findings). Prompts are particularly effective in promoting resource conservation. The study setting and the PEB level prior to the prompt intervention moderate the effect of prompts on PEB. For example, the effect of prompts was stronger in universities, hotels, and public settings compared to work settings, and when initial PEB levels were lower.