Viewed from the perspective of public policy, behavioural public policy (BPP) faces challenges in four main areas: Systems, Impatience, Nudging, and Scaling. To address these challenges, several suggestions are proposed. First, understanding how BPP interventions unfold in complex systems requires better diagnostics and the development of predictive and generative models of human behaviour. Second, the rapid pace of policy processes necessitates a shift towards generating timely and fit-for-purpose evidence. Third, maximising the opportunities presented by BPP, beyond merely ‘nudging’, demands the early and proactive application of behavioural science in the policy cycle. Fourth, achieving widespread impact in BPP initiatives means considering scale-up from the start. Lastly, the consistent and comprehensive integration of behavioural science into standard policymaking practices would support sustainable progress in addressing these challenges.

Participatory work structure is a popular concept but its causal impacts in real-world work groups have heretofore been unquantified and research has been Western-centric. We test the hypothesis that participatory group structure increases productivity for blue-collar workers in a context where participation is not a normative default. We conducted a pre-registered longitudinal field experiment with 65 Chinese factory groups (1752 workers). Half of the groups were randomly assigned to a 20-minute participatory meeting once per week for 6 weeks, in which the group's supervisor stepped aside and workers contributed ideas and personal goals in an open discussion of their work. The other half continued with status-quo meetings in which supervisors spoke and set goals, workers listened, and a researcher observed. We found that a participatory versus a hierarchical structure led to a 10.6% average increase in individual treatment workers’ productivity, an increase that endured for 9 weeks after the experiment ended. The brief participatory meetings also increased treatment workers’ retention rate (an 85% vs. 77% retention rate in treatment vs. control groups) and feelings of empowerment such as job satisfaction and sense of control. We found no evidence of informational gains or new worker goals; instead, evidence suggests that the increase in frequency of workers’ voicing opinions may have driven higher productivity. These findings provide rare causal evidence in a setting where participation is not a normative default, indicating the benefits of direct group participation for changing and sustaining behavior and attitudes.

Field experiments which test the application of behavioural insights to policy design have become popular to inform policy decisions. This study is the first to empirically examine who and what drives these experiments with public partners. Through a mixed-methods approach, based on a novel dataset of insights from academic researchers, behavioural insight team members and public servants, I derive three main results: First, public bodies have a considerable influence on study set-up and sample design. Second, high scientific standards are regularly not met in cooperative field experiments, mainly due to risk aversion in the public body. Third, transparency and quality control in collaborative research are low with respect to pre-analysis plans, the publication of results and medium or long-term effects. To remedy the current weaknesses, the study sketches out several promising ways forward, such as setting up a matchmaking platform for researchers and public bodies to facilitate cooperation, and using time-embargoed pre-analysis plans.

I’m grateful to the authors for taking the time to read and respond to the manifesto. I have great respect for the contributions each of them has made to our field, and I’d like to offer some clarifications and reflections prompted by their thoughts.

People buy some goods that they do not enjoy and wish did not exist. They might even be willing to pay a great deal for such goods, whether the currency involves time, commitment or money. One reason involves signaling to others; so long as the good exists, nonconsumption might give an unwanted signal to friends or colleagues. Another reason involves self-signaling; so long as the good exists, nonconsumption might give an unwanted signal to an agent about himself or herself. Yet another reason involves a combination of network effects and status competition; nonconsumption might deprive people of the benefits of participating in a network and thus cause them to lose relative position. With respect to real-world goods (including activities) of this kind, there is typically heterogeneity in relevant populations, with some people deriving positive utility from goods to which other people are indifferent, or which other people deplore. Efforts to measure people’s willingness to pay for goods of this kind will suggest a welfare gain, and possibly a substantial one, even though the existence of such goods produces a welfare loss, and possibly a substantial one. Collective action, private or public, is necessary to eliminate goods that people consume but wish did not exist. Legal responses here might be contemplated when someone successfully maneuvers people into a situation in which they are incentivized to act against their interests, by consuming a product or engaging in an activity they do not enjoy, in order to avoid offering an unwanted signal. Prohibitions on waiving certain rights might be justified in this way; some restrictions on uses of social media, especially by young people, might be similarly justified.

Since the publication of the seminal book Nudge by Thaler and Sunstein, several critics have highlighted preference endogeneity as a serious obstacle to nudging. When individuals hold preferences that are dynamic and endogenous to the nudge frame, it is unclear what the normative benchmark for libertarian paternalistic policies should be. While acknowledging this issue, the pro-nudging camp has not yet sufficiently addressed it. This article aims to fill this void by presenting a conditional defence of nudging when preferences are endogenous. We explain the learning process through which individuals establish ‘agentic’ preferences: preferences that are sufficiently stable, reasonable, autonomous and associated with organismic well-being to ground the ‘welfare’ principle of libertarian paternalism. To describe this process, we draw on theories from psychological science, in particular self-discrepancy theory and self-determination theory. We argue that agentic preferences are not only welfare-relevant and thus appropriate to libertarian paternalism but can also be identified by choice architects.

Some products, notably but not only platforms, increase in value for users as the number of other users increases. These interaction or network effects can result in ‘product market traps’ (Bursztyn et al., 2023) where people who use the product would be better off if they all stopped using it and switched to another product, but cannot because of coordination problems. A parallel but overlooked phenomenon is the labor market trap, where employees would be better off if they collectively left an employer, job, or profession, but cannot because of the difficulty of coordination. Product market and labor market traps pose a challenge to public policy because of the complexity of people’s behavior in networks, but can be mitigated in some cases with relatively simple taxes and regulatory interventions.

Local public managers increasingly use behavioral policy instruments to influence the behavior of citizens. However, despite their increased reliance on these instruments, there is little evidence on why local public manager would prefer behavioral instruments over classic stick, carrot or sermon-type instruments. We conduct a mixed-methods study, combining a stated-preference survey and two focus groups, to examine whether senior local public managers (directors and deputy directors) in Flanders prefer behavioral policy instruments over classic stick, carrot and sermon-type instruments, and explore whether their trust in citizens (perceptions of citizen’s ability, benevolence and integrity) affects these preferences for policy instruments. The results indicate that in some policy areas, such as health, public nuisance and road safety, public managers appear more willing to use behavioral policy instruments than classic sticks and carrots, but not sermons. Furthermore, we find that public managers’ trust in citizens does not appear to significantly affect their preferences for policy instruments, but that political and economic motives do play a role in their preferences for behavioral policy instruments. Finally, the results also indicate that the simultaneous use of behavioral and classic policy instruments (packaging) can help mediate the perceived risks of citizens’ non-compliance with behavioral policy instruments.

Recently, defaults have become celebrated as a low-cost and easy-to-implement nudge for promoting positive outcomes, both at an individual and societal level. In the present research, we conducted a large-scale field experiment (N = 32,508) in an educational context to test the effectiveness of a default intervention in promoting participation in a potentially beneficial achievement test. We found that a default manipulation increased the rate at which high school students registered to take the test but failed to produce a significant change in students’ actual rate of test-taking. These results join past literature documenting robust effects of default framings on initial choice but marked variability in the extent to which those choices ultimately translate to real-world outcomes. We suggest that this variability is attributable to differences in choice-to-outcome pathways – the extent to which the initial choice is causally determinative of the outcome.

This randomised online experiment aimed to investigate how eco-labelling and social nudging influenced sustainable food choice, as well as consider the effect of motivation to act sustainably. Participants were UK adults ≥18 years (n = 1399). Participants were asked to choose a hypothetical meal (beef, chicken or vegetarian burrito) and were randomly allocated to one of three conditions varying in labelling: eco-labelling; social nudge or control (no label). Co-primary outcomes were the frequency that the vegetarian and chicken burritos were chosen (i.e., the more sustainable food choices). There was evidence that more vegetarian (OR = 3.3 [95% CI 2.0, 5.3]) and chicken (OR = 2.5 [95% CI 1.8, 3.4]) burrito choices were made in the eco-label condition, over the beef burrito, compared to the control condition. In the social nudge condition, there was evidence that participants chose a vegetarian burrito over a beef burrito (OR = 1.7 [95% CI 1.1, 2.7]), but not a vegetarian burrito over a chicken burrito (OR = 1.4 [95% CI 0.9, 2.2]). Although both labels were effective at promoting participants to make more sustainable food choices, the eco-label was the most effective. Choice of burrito was modified by motivation to act sustainably across all conditions. This study suggests that future policy could include eco-labelling and/or a social nudge to reduce meat consumption and meet global climate change targets.

Commercial practices such as drip pricing, reference pricing and best-price guarantee can be used to set higher prices and mislead consumers, but protective measures can restore efficiency. In a placebo-controlled market experiment, we examined a treatment allowing for the use and misuse of commercial practices. Three additional treatments tested the effects of formal sanctions, informal sanctions and a regret nudge. We found that commercial practices led to higher prices, cheating was systematic and regret nudging was ineffective. Furthermore, formal and informal sanctions reduced both the likelihood of using commercial practices and the likelihood of cheating, leading to welfare increases.

The serial rapist model claims that a small number of intentional, repeat offenders are responsible for the majority of sexual assaults on college campuses. The model has formed the dominant argument for some of the most popular forms of campus intervention programs and is cited by high profile advocates and policymakers. Despite enthusiasm for the serial rapist model, it is not empirically well-supported and is contradicted by recent robust data. In this article, we ask: why does the serial rapist model have such broad and enduring appeal? In two US-based samples, one convenience and one representative, we find that people’s endorsement of the serial rapist model correlates with worldviews that cohere around ideas of a just and good status quo, and a preference for simple stories. Specifically, we find a positive relationship between endorsement of the serial rapist model and belief in a just world, system justification, social dominance orientation, need for closure and essentialism.