This essay is a write-up of my Professorial Inaugural Lecture, delivered at the London School of Economics on 9 December 2024. Herein, I describe how I became involved and have helped develop the field of behavioural public policy (BPP). I detail how the intellectual architecture of BPP – its journal, Annual International Conference and Association – came into existence, and allude to my hopes for how the field might develop as we go forward.

Interventions are to the social sciences what inventions are to the physical sciences – an application of science as technology. Behavioural science has emerged as a powerful toolkit for developing public policy interventions for changing behaviour. However, the translation from principles to practice is often moderated by contextual factors – such as culture – that thwart attempts to generalize past successes. Here, we discuss cultural evolution as a framework for addressing this contextual gap. We describe the history of behavioural science and the role that cultural evolution plays as a natural next step. We review research that may be considered cultural evolutionary behavioural science in public policy, and the promise and challenges to designing cultural evolution informed interventions. Finally, we discuss the value of applied research as a crucial test of basic science: if theories, laboratory and field experiments do not work in the real world, they do not work at all.

This article reports on a survey study comparing the general public's attitude towards nudging to its attitude towards the traditional tools of government: information, subsidies, taxes and mandates. The study was based on responses from a representative sample of the adult Swedish population. In separate evaluations, the respondents rated how positively or negatively they perceived a set of specific policy tools, traditional and behavioral, across different policy goals. Overall, information and subsidies were more positively perceived than the other types of policy tools, nudging included. Respondents’ attitudes towards the policy tools were partly explained by individualistic ideological views, whether they agreed with the intended policy goals, and certain socio-demographic variables. Implications for future research and public policy are discussed.

Communicating evidence that a policy is effective can increase public support although the effects are small. In the context of policies to increase healthier eating in out-of-home restaurants, we investigate two ways of presenting evidence for a policy's effectiveness: (i) visualising and (ii) re-expressing evidence into a more interpretable form. We conducted an online experiment in which participants were randomly allocated to one of five groups. We used a 2 (text only vs visualisation) × 2 (no re-expression vs re-expression) design with one control group. Participants (n = 4500) representative of the English population were recruited. The primary outcome was perceived effectiveness and the secondary outcome was public support. Evidence of effectiveness increased perceptions of effectiveness (d = 0.14, p < 0.001). There was no evidence that visualising, or re-expressing, changed perceptions of effectiveness (respectively, d = 0.02, p = 0.605; d = −0.02, p = 0.507). Policy support increased with evidence but this was not statistically significant after Bonferroni adjustment (d = 0.08, p = 0.034, α = 0.006). In conclusion, communicating evidence of policy effectiveness increased perceptions that the policy was effective. Neither visualising nor re-expressing evidence increased perceived effectiveness of policies more than merely stating in text that the policy was effective.

Behavioural science has found growing application in applied public policy settings, offering a vast literature to bring to bear on apparent cognitive errors. The potential, however, is not without peril. Policymakers and scholars may draw unwarranted confidence that successful behavioural interventions from elsewhere will replicate in their institutional settings. In this research, I partner with Minneapolis Public Housing and use a design-based approach to identify interventions that can reduce eviction actions. This study presents three vignettes that demonstrate and categorize the mistakes behavioural science can make when it fails to understand how formal and informal institutional features influence decision-making. But, in integrating methods and theories from the design sciences, public policy and public administration, we have the potential to create behavioural interventions that fit the social context.

The present study investigates the relation of procedural transparency and compliance with authorities’ regulations. The underlying assumption is that procedural transparency encourages compliance with regulations. In an incentivized experiment, 666 participants took on the role of a business owner and had to fill in a form and spend a certain amount of their income as compliance costs to adhere to safety rules. In a 2 (Business Size: small vs big) × 2 (Penalty Rate: equal vs unequal) × 2 (Penalty Scheme: transparent vs nontransparent) between-subjects design, we investigated whether an unequal penalty rate for small-size in contrast to big-size businesses had a different effect on compliance when this difference was transparent compared to when it was not transparent. Business income, compliance costs, and audit probability were varied within-subject, over 18 decision rounds. We find that the deterring effect of a higher penalty rate for big-size compared to small-size businesses under a nontransparent unequal penalty scheme is attenuated when the same information is available. This supports the idea of a backfiring effect and suggests that authorities need to carefully consider what information about their procedures to communicate in order to avoid the unintended negative effects of increasing transparency.

In October 2021, a majority of the UK gambling industry implemented a new UK safer gambling message, ‘take time to think’, which features on gambling advertising and websites. An effective safer gambling message could plausibly affect several relevant gambling behaviours, with previous research suggesting that message effectiveness is maximised via messages that are displayed prominently immediately prior to gambling. We experimentally tested this message's effect on four contemporaneous gambling behaviours (the proportion of available funds bet, clicks for help service information, the mean speed of play, and the total number of roulette spins made) in an incentivised online roulette game in a sample of UK-based online gamblers. Participants (n = 2,305) were randomly allocated to either (a) ‘no-message’ control, (b) ‘message’ shown throughout the condition or (c) a ‘message+’ condition, where the message was shown throughout and also via a popup immediately prior to the roulette game. Overall, the results showed no credible effects across the four outcome measures when comparing either of the message conditions to the no-message control. Even the prominent display of the ‘take time to think’ message did not lead to credible beneficial effects on a range of contemporaneous gambling behaviours.

Behavioural public policy is increasingly interested in scaling-up experimental insights to deliver systemic changes. Recent evidence shows some forms of individual behaviour change, such as nudging, are limited in scale. We argue that we can scale-up individual behaviour change by accounting for nuanced social complexities in which human responses to behavioural public policies are situated. We introduce the idea of the ‘social brain’, as a construct to help practitioners and policymakers facilitate a greater social transmission of welfare-improving behaviours. The social brain is a collection of individual human brains, who are connected to other human brains through ‘social cues’, and who are affected by the material and immaterial properties of the physical environment in which they are situated (‘social complex’). Ignoring these cues and the social complex runs the risk of fostering localised behavioural changes, through individual actors, which are neither scalable nor lasting. We identify pathways to facilitate changes in the social brain: either through path dependencies or critical mass shifts in individual behaviours, moderated by the brain's property of social cohesion and multiplicity of situational and dispositional factors. In this way, behavioural changes stimulated in one part of the social brain can reach other parts and evolve dynamically. We recommend designing public policies that engage different parts of the social brain.

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.

There is growing public concern about the ‘unfairness’ of many pricing practices that have become common in consumer, particularly digital, markets. Industrial and behavioural economists have developed theories that explain the conditions under which these practices are profitable for firms, and their implications for consumer welfare. We identify a mismatch between the welfare economic principles used in this theoretical work and the normative perspective in which these practices are viewed as unfair. We develop a concept of ‘transactional fairness’, grounded in the normative approach of Sugden's Community of Advantage, that is reflective of public concerns. Transactional fairness is complementary to established criteria of economic efficiency and distributional equity but is based entirely on the relationship between individual buyers and sellers. It establishes clear principles with realistic information requirements that are appropriate for compliance by firms. Regulation based on this approach can help to restore public faith in markets.

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.

Small and medium-sized enterprises constitute the largest share of companies in most economies. As major resource users and significant contributors to environmental pollution, they are relevant targets for public policy programs aimed at increasing sustainability. We study how ‘sludge’ – small frictions in the choice architecture – can impact the uptake and effectiveness of such public policy programs targeted at SMEs. To this end, we conducted a field experiment within an existing policy program designed to support SMEs in implementing cost-effective environmental management practices. We manipulated the process of receiving free green items intended to support the implementation of those environmentally friendly practices within firms. We find that sludge, in the form of minor additional effort required to order the items, substantially undermined the program’s effectiveness. These results have important implications for policymakers: even minor sludge in the choice architecture can seriously impair the effectiveness of public policy programs targeted at companies.

The COVID-19 pandemic provided a stark reminder that societies will struggle to address global challenges unless they are able to change behaviour at scale. The widely adopted ‘nudge’ approach epitomizes an individualistic, deficit model of human cognition and motivation that leverages or overcomes people’s weaknesses and biases to get them to do things they would otherwise not. By contrast, we argue that tackling the challenges facing humanity requires a collective, capacity-building approach – one that boosts the competences, opportunities, and motivations of individuals to act together.