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.

Transparency is intimately linked to debates about the ethics, political legitimacy and effectiveness of nudging. This paper provides an overview of empirical studies investigating how changes in the transparency of a nudge affect people's choices and evaluations of the nudge. I conclude that the present literature provides generally consistent evidence supporting that the effectiveness of a nudge does not decrease when choosers are given good opportunity to detect and understand the influence it might have on their choices. However, several conceptual and methodological issues are identified, significantly limiting the scope of the conclusions that can be drawn. The limitations are discussed and organized into six themes, with recommendations provided for how future research may address them.

Cooperative and caring behaviors are key drivers of human social progress, especially during catastrophes or pandemic events. While COVID-19 pandemics was arriving to Colombia in absence of any approved therapeutic strategy or vaccine, and based on evidence from other viral diseases, we anticipated to hypothesize the protective role of some nutritional supplements such as Vitamin D and C against SARS-CoV2. Therefore, for health workers, we proposed a voluntarily nutritional supplementation plan to fortify their immune system aiming to prevent or mitigate eventual COVID-19 infection and disease. Using the behavioral EAST framework, all our health workers (n = 1,063) were invited via email to participate voluntarily in a supplementation strategy for a period of 3 months. 77.4% accepted participation, and among them, we identified a group with optimal adherence to the proposed supplementation plan (20%) and a predominant group with no adherence at all (57.29%). Adherence seemed to be associated to a risk perception bias that was predominant in female workers and those workers performing in working areas with higher risk of infection. Of importance, adherence to the supplementation strategy was associated to a lower percentage of COVID-19 diagnostics (12%) as compared with that observed in non-adherence participants (19%). Moreover, the sustained adherence during the time of intervention seemed to promote adoption of this target behavior, as up to 35% of the adherent participants remained attached (on their own) to the supplementation habit, 3 months after the end of the intervention. All these data show the potential relevance of EAST frameworks as tools to trigger health care and altruistic behaviors to avoid the spread of pandemic diseases. In line with other authors, our observations suggest that nutritional vitamin D and C supplementation could mitigate the risk of COVID-19, highlighting the behavioral and biological relevance of this type of interventions during emerging or re-emerging infectious diseases.

This study investigates the impacts of behavioral finance on stock market volatility. The primary aims are to explain the reasons behind changes in the S&P 500 price within the context of behavioral finance and to analyze investor behavior in response to these changes. To achieve this, the research employs time-series analysis over a 10-year period, focusing on the S&P 500, real interest rates, consumer confidence, market volatility and credit default swaps while considering the effects of behavioral biases. The findings reveal several significant correlations: rising real interest rates negatively affect stocks due to loss aversion and sentiment. Conversely, higher consumer confidence tends to positively influence the stock market, driven by herding behavior and optimism. Additionally, market volatility shows a negative correlation with the S&P 500, influenced by risk aversion, recency bias and herding behavior. Moreover, an increase in credit default swap rates leads to stock market declines, primarily influenced by risk perception, loss aversion and herding behavior.

Financial policymakers increasingly rely on behavioural insights to protect the interests of consumers. However, little is known about how citizens feel about interventions designed to nudge their financial behaviour. Most literature on the acceptability of behavioural interventions focuses on the health domain. To address this gap, we present the results of an experiment on the acceptability of seven financial behavioural interventions (N = 684, members of a panel of the Dutch Authority for the Financial Markets). We investigate the role of the agent implementing the intervention (policymaker versus financial company) and perceived effectiveness in relation to the acceptability of these interventions. The acceptability of behavioural interventions in financial decision-making appears to be lower than the acceptability levels found in previous studies. We find no effect of the agent on acceptability. Perceived effectiveness is strongly correlated with acceptability, but only perceived effectiveness in influencing one's own decisions has a consistently positive relationship with acceptability. Perceived effectiveness in influencing others' decisions has either no, a positive, or a negative relationship with acceptability. These results highlight that acceptability appears to be at least partly domain-specific and show that we have only just begun understanding the acceptability of behavioural interventions and its drivers.

We conducted a large-scale online experiment to examine whether climate change messaging can induce emotions and motivate pro-environmental action. We study how exposure to explicit positive (‘warm glow’) and negative (‘cold prickle’) emotional appeals as well as a traditional social norm communication affects pro-environmental action. We find that a simple call to take action to mitigate climate change is at least as affective as social norm message framing and emotional appeals. Our results highlight the difficulty of designing messaging interventions that effectively harness emotional incentives to promote pro-environmental action. Messages that explicitly emphasise the personal emotional benefits of contributing to environmental causes or the adverse emotional effects of not doing so seem to fall short of motivating pro-environmental effort. Our findings underscore the need for caution when incorporating emotive appeals into policy interventions.

Behavioural science has sought to promote pro-environmental behaviours including climate-friendly dietary change, and to reduce travel emissions and excessive wastes. Nevertheless, there is a debate about how effective behavioural interventions are, and in turn, about the real barriers to enduring pro-environmental behaviour change. In this context, we conceptualise brown sludge as multi-level impediment to pro-environmental behaviour change, which results in higher environmental costs shared by the broader society, rather than solely by the individual actor. We propose that brown sludge comprises an array of additional transaction costs, encompassing, but not restricted to, psychological, temporal, and uncertainty costs. Brown sludge can occur at the individual, social, institutional, and societal levels. Examples include confusing eco-information, delay and disinformation campaigns, and complicated systems and infrastructure leading to carbon lock-in.

Many foodborne illness outbreaks originate in food service establishments. We tested two behavioural interventions designed to improve the duration and quality of handwashing. We ran a three-armed parallel trial in a laboratory kitchen, from 7 March to 27 May 2022. Participants were n = 195 workers who handle food. We randomly allocated participants to three groups: Timer – tap-mounted timer that counted seconds while participants washed their hands; Precommitment – agreed to five statements on good hand hygiene before attending the kitchen; and Control. Participants completed a food preparation task under time pressure. Cameras focused on the sink captured handwashing. Outcome measures were number of times participants washed their hands; number of times they washed their hands using soap; number of times they washed using soap and washed the backs of their hands; and mean duration of handwashing attempts using soap. Participants in Timer washed their hands for 1.9 s longer on average than Control (β = 2.20, 95% CI = 0.34-4.06, p = 0.021). Participants in Precommitment washed their hands for 2.5 s longer on average than Control (β = 2.30, 95% CI = 0.33-4.27, p = 0.022). We found no statistically significant differences on any other outcome measure.

This study examines how beliefs interact with heterogeneous donation preferences in determining people's donation decisions and choices of revision and observability. We conducted an online experiment eliciting participants’ first-order beliefs, that is, beliefs about an average donor's contribution, with the opportunity of being recognized. We also provided the opportunity for donation revision to a group of randomly selected participants. Our study results show that people's first-order beliefs are positively correlated with their willingness to donate and their actual donations. Moreover, first-order beliefs also interact with people's heterogeneous donation preferences in jointly determining their decisions of donation revision and observability – their tendency to opt in for public recognition. Donors with low first-order beliefs and high donation preferences are most likely to opt in for recognition, but they are unlikely to revise their donations. Donors with high first-order beliefs and low donation preferences are most likely to revise their donations, but they are less likely to choose to be recognized. Donors with low first-order beliefs and low donation preferences display the lowest tendency toward revision and observability.

Consequentialist theories of the behavioral state are largely grounded in satisfying self-interested preferences through policies that employ choice architecture and related strategies to encourage rational decision-making. Even when allowing for free choice, however, this stance tends to be characterized by a paternalistic ‘view from nowhere’ that may not fully accommodate a plurality of values. Alternative approaches such as contractarianism position policy in the context of marketplace exchange, bolstered by shared beliefs in the legitimacy of social institutions. Yet this view may not sufficiently consider issues of asymmetric access, or ideological frames that do not see these institutions as legitimate. To address these deficits, we propose the value of a dialogical approach to behavioral public policy that facilitates collaborative engagement and behavioral justice to redress asymmetries and inequities through a more discursive approach, which builds on practices employed by design for public policy. In so doing, this political theory suggests an actionable counterpoint to paternalistic and competition-based conceptions of the State to address frame plurality and increase the potential for system equity.

This paper explores the complexities and unintended consequences of conflict of interest (COI) disclosures in various professional settings. It highlights key psychological processes encountered by recipients of such disclosures. Notably, it describes the burden of disclosure effect, which paradoxically reduces trust while increasing compliance due to social pressures, and disclosure's expertise cue, where disclosures inadvertently increase trust and persuasiveness by signalling expertise. The paper also outlines best practices for improving COI disclosures, emphasising the need for external third-party involvement and encouraging deliberation. It concludes that effective disclosure depends not only on how recipients process information but also critically on how the disclosure influences the behaviour of advisors, underscoring the need for a holistic approach to managing COIs that goes beyond mere transparency. A version of this paper was presented as a keynote at the Second Annual International Behavioural Public Policy Conference at the University of North Carolina in September 2023.

Similarly to other domains of the social sciences, behavioural science has grappled with a crisis concerning the effect sizes of research findings. Different solutions have been provided to answer this challenge. This paper will discuss analytical strategies developed in the context of computational social science, namely causal tree and forest, that will benefit behavioural scientists in harnessing heterogeneity of treatment effects in RCTs. As a mixture of theoretical and data-driven approaches, these techniques are well suited to exploit the rich information provided by large studies conducted using RCTs. We discuss the characteristics of these methods and their methodological rationale and provide simulations to illustrate their use. We simulate two scenarios of RCTs-generated data and explore the heterogeneity of treatment effects using causal tree and causal forest methods. Furthermore, we outlined a potential theoretical use of these techniques to enrich behavioural science ecological validity by introducing the notion of behavioural niche.

Companies face increasing pressure to adopt social responsibility initiatives while simultaneously providing shareholder value. However, consumers may respond negatively to ‘win-win’ initiatives that benefit society while bringing financial gain to the corporation, producing a backlash effect. Previous researchers have attributed this backlash effect to the violation of a communal relationship norm that companies trigger in consumers when communicating their win-win initiatives. We propose the alternative hypothesis that the backlash derives from people's deception aversion. We find evidence supporting deception aversion in three preregistered studies showing that companies are evaluated negatively when their actions differ from those implied by their stated prosocial policy and not, as predicted by the communal norm violation hypothesis, when they merely earn a profit. Our results suggest that companies should not fear that earning a profit from prosocial activities will carry reputational risk, so long as they are transparent.

Compliance with hygiene and other safety measures in the workplace was an important component of society's strategy for reducing infections at the onset of the COVID-19 pandemic, in particular before vaccinations were widely available. We report the results of a field trial of well-established behavioural interventions (social norms, pledging and messenger effects) we implemented to improve compliance with such measures in an occupational setting. We use daily reports of own and other's behaviour to assess the effects of these interventions and supplement these subjective (self-reported) measures with objective data on hand sanitiser usage. The behavioural interventions tested have statistically significant but quantitatively moderate effects on subjective compliance measures and minimal effects on hand sanitiser usage. All effects of our interventions are short-term in nature and dissipate shortly after implementation. Our findings thus provide at most weak support for the notion that typical behavioural interventions can help support compliance with infection prevention measures in the workplace.

Boosts and nudges are two separate types of behavioral public policies, distinguished by the mechanisms through which they operate. We investigated whether this theoretical distinction translates into different effects when instances of these policy types are implemented in the context of energy consumption. In a long-term field randomized controlled trial, we competitively tested boosts against nudges. We found that boosts outperform nudges throughout a seven-month period in a student dormitory setting – both in terms of accumulated energy savings, as well as in keeping consumption consistently low during the experimental period. Furthermore, we explored the processes behind the boosts and nudges through a number of mechanistic markers and showed that the tested interventions indeed are instances of the respective types.

Political scientists have proposed that party cues can be used to compensate for the public's well-documented lack of substantive political knowledge, but some critics have argued that applying party cues is more difficult than assumed. We argue that this debate has proven intractable in part because scholars have used ambiguous normative criteria to evaluate judgments. We use a unique task and clear normative criteria to evaluate the use of party cues in making political judgments among two samples: a sample of state legislators and an online sample of the public. We find that the public sample performs poorly when using cues to make judgments. State legislators make much more accurate judgments on average than even the most attentive segment of the public and are more likely to place less weight on irrelevant cues when making judgments, although there is evidence that both samples performed worse with the inclusion of non-diagnostic cues. We conclude with a discussion of the relevance of the results, which we interpret as showing that party cue use is more difficult than theorized, and discuss some practical implications of the findings.

Why are take up rates incomplete or low when the relevant opportunities are unambiguously advantageous to people who are eligible for them? How can public officials promote higher take up of opportunities? All over the world, these are challenges of the first order. There are three primary barriers to take up: learning costs, compliance costs, and psychological costs. These costs lower the net expected benefit of opportunities, and reduce participation in otherwise advantageous programs. Fully rational agents would consider these costs in their take up decisions, and in light of behavioral biases, such costs loom especially large and may seem prohibitive. Experimental and other evidence suggest methods for reducing the barriers to take up and the effects of behavioral biases. Use of such methods has the potential to significantly increase access to a wide range of opportunities that would increase individual well-being and social welfare.

Meat-based food production has a detrimental impact on the environment and health. In response, Veganuary (an international non-profit organisation) encourages people to go vegan each January. We investigated the effects of a Veganuary campaign in workplace cafeterias which increased the availability and salience of plant-based products. We conducted an interrupted time series analysis on a large dataset from a UK catering company, which comprised 2,255,404 meals sold between 2016 and 2022, with Veganuary activity starting from 2019. Analysis indicated that Veganuary activity had a positive effect on sales of vegan products in 2020, 2021 and 2022, estimated at an initial increase of 86–113% in the proportion of weekly sales (relative to the baseline, depending on year). The effects of the 2020 and 2021 campaigns were still present – at approximately one third of their initial magnitude – one year following the campaigns. There was a positive effect on vegetarian products in 2019, 2021 and 2022; initial effects were smaller – 23–79% – due to higher levels of pre-campaign consumption. The effects of the 2019 and 2021 campaigns endured, with a small impact present after one year for 2019 and six months for 2021.