Pro-environmental behavior: a reflection on the effectiveness of the main strategies used in past experiments

The goal of this paper is to review experimental evidence on pro-environmental behavior (PEB). The ultimate objective is to identify the most effective strategies in terms of activating or modifying PEBs, especially on the long-term. We classify experiments into four categories. First, we review experiments that use the power of social influence, which is most effective when norm salience is high, group references are specified, or social identities are of particular relevance to one's self-concept. Second, we review experiments that show how psychological biases affect PEB, as evidenced by the better-than-average effect, strategic ignorance, cognitive dissonance, PEB mental accounting, and prospect theory. We discuss the impact of nudging to obtain the desired PEB and provide new insights on which nudges are more likely to affect a given type of PEB. Third, we review motivational strategies that have focused on commitment, but neglect the role of moral norms and environmental (self-) identity. Fourth, we review experiments showing that whatever the strategy adopted to activate or modify PEBs, psychological or physical barriers can prevent the occurrence of PEB. Finally, we provide guidance to the interested reader on methodological aspects, discuss ethical issues, and offer an agenda for future research. Overall, this review confirms the central role of the "self" in the promotion of PEB. The strategies reviewed are most effective when individuals' self-concept is involved and aligned with pro-environmental objectives. Intrinsic motivation appears to be a decisive determinant of (long-term) PEB.