The use of behavioural sciences in government has expanded and matured in the last decade. Since the Behavioural Insights Team (BIT) has been part of this movement, we sketch out the history of the team and the current state of behavioural public policy, recognising that other works have already told this story in detail. We then set out two clusters of issues that have emerged from our work at BIT. The first cluster concerns current challenges facing behavioural public policy: the long-term effects of interventions; repeated exposure effects; problems with proxy measures; spillovers and general equilibrium effects and unintended consequences; cultural variation; ‘reverse impact’; and the replication crisis. The second cluster concerns opportunities: influencing the behaviour of government itself; scaling interventions; social diffusion; nudging organisations; and dealing with thorny problems. We conclude that the field will need to address these challenges and take these opportunities in order to realise the full potential of behavioural public policy.

Some of the challenges in Sanders et al. (2018, this issue) can be aptly illustrated by means of charity nudges; that is, nudges designed to increase charitable donations. These nudges raise many ethical questions. First, Oxfam's triptychs with suggested donations are designed to increase giving. If successful, do our actions match ex ante or ex post preferences? Does this make a difference to the autonomy of the donor? Second, the Behavioural Insights Team conducted experiments using social networks to nudge people to give more. Do these appeals steer clear of exploiting power relations? Do they respect boundaries of privacy? Third, in an online campaign by Kiva, donors are asked to contribute directly to personalised initiatives. In many cases, the initiative has already been funded and donor money is funnelled to a new cause. Is such a ‘pre-disbursal’ arrangement truthful and true to purpose as a social business model?

In a ‘post-truth’ era in which personality and opinion trump evidence and reason, the need for frankness in debates about the use and boundaries of science and policy is high. We welcome the reflective and nuanced approach to behavioural science in policy-making in Sanders, Snijders and Hallsworth's (2018) piece. Despite our support for the approach in this paper, we suggest that there are deeper issues than are currently acknowledged. Our critique tackles three issues: the empirical, the normative and the political. In the first section, we examine what counts as ‘behavioural’ and how this label is used to legitimate a range of policy activities. We then look at randomised controlled trials in the next section, highlighting the extra-scientific dimensions of the empirical ‘What Works’ revolution. Finally, we question some ontological assumptions that drive empirical research and its translation into policy, asking where the collective is to be found in behavioural public policy.

The Behavioural Insights Team (BIT) has led in the promotion and adoption of behavioural science research in public policy. This comment addresses a number of issues that must be faced by BIT and the wider behavioural public policy agenda as the field becomes institutionalised and normalised within public policy internationally, in particular issues of ethics and professional codes.

During the last decade, the Behavioural Insights Team (BIT) has been the main driver of establishing behavioural public policy as a novel approach in public policy. Adhering to a set of strategic principles, BIT has succeeded in translating insights from the behavioural science literature into policy interventions to show how behavioural science may be applied to public policy in a methodologically as well as economically efficient way. However, as Sanders, Snijders and Hallsworth (2018) note in their paper, the wide-ranging transformation of public policy development that many thought possible has remained absent. In this comment, I argue that this situation itself is due, at least partly, to the strategic principles adopted by BIT, and I call for developing more ‘diagnostic’ approaches, including better tools and models, to ensure that behavioural science is not perceived as offering merely technocratic tweaks.

There are inherent differences in the priorities of academics and policy-makers. These pose unique challenges for teams such as the Behavioural Insights Team (BIT), which has positioned itself as an organisation conducting academically rigorous behavioural science research in policy settings. Here we outline the threats to research transparency and reproducibility that stem from working with policy-makers and other non-academic stakeholders. These threats affect how we perform, communicate, verify and evaluate research. Solutions that increase research transparency include pre-registering study protocols, making data open and publishing summaries of results. We suggest an incentive structure (a simple ‘nudge’) that rewards BIT's non-academic partners for engaging in these practices.

Socially minded nudges are the more sociable cousin of regular nudges: they reveal important information about other people's behavior, raise normative expectations about what is desirable, can be shared and transmitted online or offline and leverage social incentives and sanctions that regulate individual and group behavior. In this article, I argue that many of the most successful nudges – that is, nudges that have been well replicated, offer positive spill-over and whose effects last over time – have in fact been social nudges. Moreover, the efficacy of other nudges can be enhanced by considering the social dimension of the problem that they are trying to address. In asking where behavioral science should go next, I argue that although the Behavioural Insights Team has traditionally shied away from addressing more complex and sticky societal issues, socially situated nudges are particularly well suited to address many of the important challenges raised by Sanders et al. (2018).

Behavioral public policies are aimed at influencing the behavior of the public in a way that is advantageous for the public itself and within the law. Sanders, Snijders and Hallsworth (2018, this issue) summarize the state of the art of this new field of study and introduce a number of challenges and opportunities for the time to come. We address an additional challenge that is present and central in all attempts to influence behavior, namely the public – the people that are the target of behavioral public policies. We review evidence revealing that people do not passively accept those influence attempts, but often show reactant responses. We propose that the Persuasion Knowledge Model provides a framework both to understand the reactions of the public and to facilitate communication between academic researchers and practitioners.

This paper is a response to Sanders, Snijders and Hallsworth (2018). The challenges and opportunities of behavioural public policy Sanders, Snijders and Hallsworth discuss highlight a conundrum for the field: the impact of behavioural interventions is difficult to measure accurately in complex situations, and yet complexity is inherent in the very areas in most need of impact. Behavioural interventions will be only one tool of many to work towards broader organisational, systems and social change. As a field, we should be looking to other disciplines, inviting them into the fold of discussions on how to achieve these changes. Finally, while the mantra of nudge for good is a useful beacon, intentions are only part of the equation, and a number of questions should be asked when considering a behavioural policy intervention.

The application of behavioural insights to public policy has been a success story of recent years, in academia and in the civil service. Alongside this, a parallel group of practitioners has emerged, using the same underlying research to pursue commercial and marketing goals. Although the objectives are mostly different, many of the approaches are similar. This article contrasts public and private sector approaches and highlights lessons each group can learn from the other.

The problem with decision-making in an institutional setting is that it is often more important for one's reputation and job security to appear to be logical than it is to be truly effective. Indeed, a far lower burden of proof is applied to ideas and suggestions that accord with simple economic axioms than to those that are oblique, counterintuitive or employ second-order thinking. Hence, the best new ideas generated by behavioural science will and should often lie outside the bureaucrat's natural comfort zone; any difficulties encountered by behavioural scientists should not surprise us: like the sting of an antiseptic, they are proof that the treatment is working.

This article discusses some of the political barriers to the adaption of behavioural approaches to public policy. It contrasts the increasing acceptance of behavioural ideas in the civil service with the limited enthusiasm displayed, so far, by politicians. It also suggests that more attention should be focused on the impact of those affected by behavioural initiatives.

While behavioral public policy remains underutilized in rich countries relative to its potential impact, the required infrastructure for diagnosing behavioral bottlenecks and the autonomy to act on those diagnoses are even less common in developing countries. At the World Bank, the Mind, Behavior, and Development Unit (eMBeD) aims to promote the systematic use of behaviorally informed tools in development policies and projects, institutionalize the use of behavioral science in development organizations and governments, provide evidence on scaled and sustainable behavioral solutions, and generate more and better behavioral data. By focusing on thorough diagnosis and ongoing adaptation, we aim to create impactful, behaviorally informed interventions in complex, resource-constrained settings. While Sanders, Snijders and Hallsworth (2018) raise valuable points about the implications for impactful behavioral public policy, for those working in developing countries, issues of replication and scale come with unique contextual challenges.