Filippos Exadaktylos ¹ Ximeng Fang ^2* Mehdi Farsi ³

• ¹ University of Barcelona, Barcelona, Catalonia, Spain
• ² Saïd Business School, Social Sciences Division, University of Oxford, Oxford, United Kingdom
• ³ Université de Neuchâtel, Neuchâtel, Neuchâtel, Switzerland

Our actions and choices in one situation today can affect how we act in another situation tomorrow. There is growing interest in the existence and relevance of such "behavioral spillovers" by academics and policy makers alike, as significant spillovers from one behavioral domain to another domain can have profound implications for the evaluation of policies and interventions aimed at encouraging behavioral change, for example in the pro-environmental and prosocial domains. Yet, the evidence on the direction and magnitude of spillovers is mixed, which is perhaps unsurprising given that such effects are likely to be highly context-dependent and may involve a complex set of psychological mechanisms such as moral licensing or consistency concerns. This Research Topic presents a collection of five contributions that aim at advancing our understanding of behavioral spillovers and their underlying mechanisms.Two contributions focus on spillovers in pro-environmental behavior and attitudes. Dreijerink, Handgraaf, and Antonides examine how spillovers across pro-environmental behaviors may be affected by their perceived similarity. Using a survey in a representative Dutch sample (n = 1,536), the authors present various pro-environmental behaviors to respondents and ask them to group behaviors based on how naturally they "went together". Six main clusters are identified based on concreteness, impact, and location. The authors find that stronger engagement in pro-environmental behaviors are often positively correlated with desire to engage in other behaviors within and across clusters. This suggests that spillover effects may be possible both when actions are perceived as similar and as less similar, but their study also indicates that these effects may not be uniform; some combinations of behaviors are more likely to spill over than others. These results suggest that similarity between actions-whether conceptual or based on effort-plays a significant role in facilitating behavioral spillovers within a domain. However, causality remains uncertain, emphasizing the need for further exploration.In the next contribution, Castro Santa, Drews, and van den Bergh conduct an incentivized online experiment with 1,985 individuals on MTurk to investigate how the purchase of green products causally affects (i) follow-up purchase decisions and (ii) support for climate policies. They created exogenous variation in initial green purchases by randomly assigning participants to a virtual shop with either predominantly green or predominantly conventional products. Interestingly, the authors observe positive spillovers on green purchases in a subsequent shopping task, but negative spillovers on environmental policy support, with little evidence for moderating effects of pro-environmental identity or moral licensing. These results highlight the complex nature of spillover effects even within the pro-environmental domain.Hofmeier and Strang focus on prosocial behavior and investigate whether past (monetary) donation environments can influence subsequent donations. To do so, they conducted two laboratory experiments in Germany in which the initial donation amount of some subjects is publicly observable, while others make their choice in private. They then test whether observability has effects on a second donation opportunity that is kept private for all subjects. While donation levels are relatively high and consistent across the two donation choices, the authors find only weak effects of observability on the initial donation amount and no evidence of effects on the second donation. Although this is partially unexpected in light of previous studies on social image concerns, cleanly identified null results also add important contributions to scientific knowledge. While the above-mentioned studies focus on spillover effects within broadly the same domains, the final two contributions investigate the relevance of cross-domain interactions. Sahai and Manjaly provide insights into whether making a decision involving economic trade-offs could influence subsequent moral evaluations, for example through the activation of certain mindsets. In particular, the authors focus on risky lottery choices as a prior behavior and different versions of the trolley dilemma as a consequent moral evaluation. Across two experiments with a total of 320 university students in India participating, they find that individuals who are randomly assigned to face a number of lottery choices at first are more likely to make utilitarian (as opposed to deontological) choices in certain types of hypothetical moral dilemmas. Additional evidence points to the activation of cost-benefit reasoning as an explanatory mechanism. The study also speaks to the broader question of how markets and economic interactions affect morality.Finally, Krupka et al. explore how multiple social identities-political and non-political (university)-interact to shape perceptions of social norms, demonstrating a form of psychological spillover from one domain (political identity) to another (university norms).In their longitudinal study of U.S. university students during the COVID-19 pandemic, they find that political identity influences how students perceive and interpret norms regarding health measures, even in a non-political university setting. Despite incentivizing accurate norm perception, political identity still dominated, showcasing how a salient identity can cloud norm perception in other social contexts, leading to cross-domain spillovers in norm perception. This study underlines the critical role of social identities in driving spillovers and how they can influence behaviors in seemingly unrelated domains.Collectively, these studies enhance our understanding of behavioral spillovers by highlighting the complexity and variability of how one behavior influences subsequent actions across different domains. The research shows that spillovers can be both positive (e.g., increased pro-environmental consumption after green purchases) and negative (e.g., reduced climate policy support after engaging in green consumption), depending on factors such as the similarity between the behaviors, the context, and individual psychological processes like identity and perceived effort. A key theme that emerges is that behavioral spillovers are not automatic or universal; they depend heavily on the relationship between the initial and subsequent actions. When behaviors are similar or perceived as part of the same category, positive spillovers tend to occur, fostering consistency. However, when behaviors differ in context or perceived cost, negative spillovers, such as moral licensing or reduced policy support, can emerge. This body of work also emphasizes the limits of relying on image concerns or individual actions to foster broader, more impactful behavioral change. Instead, it underscores the need to consider how promoting one behavior might inadvertently reduce engagement in other, often more consequential actions, such as supporting systemic policies. Thus, we learn that behavioral spillovers are shaped by a combination of individual identity, external incentives, and the cognitive connections people make between behaviors, making them crucial factors in designing interventions aimed at promoting sustainable, long-term behavioral change.