This paper evaluates the state of contact hypothesis research from a policy perspective. Building on Pettigrew and Tropp's (2006) influential meta-analysis, we assemble all intergroup contact studies that feature random assignment and delayed outcome measures, of which there are 27 in total, nearly two-thirds of which were published following the original review. We find the evidence from this updated dataset to be consistent with Pettigrew and Tropp's (2006) conclusion that contact “typically reduces prejudice.” At the same time, our meta-analysis suggests that contact's effects vary, with interventions directed at ethnic or racial prejudice generating substantially weaker effects. Moreover, our inventory of relevant studies reveals important gaps, most notably the absence of studies addressing adults' racial or ethnic prejudices, an important limitation for both theory and policy. We also call attention to the lack of research that systematically investigates the scope conditions suggested by Allport (1954) under which contact is most influential. We conclude that these gaps in contact research must be addressed empirically before this hypothesis can reliably guide policy.

Why does public conflict over societal risks persist in the face of compelling and widely accessible scientific evidence? We conducted an experiment to probe two alternative answers: the ‘science comprehension thesis’ (SCT), which identifies defects in the public's knowledge and reasoning capacities as the source of such controversies; and the ‘identity-protective cognition thesis’ (ICT), which treats cultural conflict as disabling the faculties that members of the public use to make sense of decision-relevant science. In our experiment, we presented subjects with a difficult problem that turned on their ability to draw valid causal inferences from empirical data. As expected, subjects highest in numeracy – a measure of the ability and disposition to make use of quantitative information – did substantially better than less numerate ones when the data were presented as results from a study of a new skin rash treatment. Also as expected, subjects’ responses became politically polarized – and even less accurate – when the same data were presented as results from the study of a gun control ban. But contrary to the prediction of SCT, such polarization did not abate among subjects highest in numeracy; instead, it increased. This outcome supported ICT, which predicted that more numerate subjects would use their quantitative-reasoning capacity selectively to conform their interpretation of the data to the result most consistent with their political outlooks. We discuss the theoretical and practical significance of these findings.

When people make decisions with a pre-selected choice option – a ‘default’ – they are more likely to select that option. Because defaults are easy to implement, they constitute one of the most widely employed tools in the choice architecture toolbox. However, to decide when defaults should be used instead of other choice architecture tools, policy-makers must know how effective defaults are and when and why their effectiveness varies. To answer these questions, we conduct a literature search and meta-analysis of the 58 default studies (pooled n = 73,675) that fit our criteria. While our analysis reveals a considerable influence of defaults (d = 0.68, 95% confidence interval = 0.53–0.83), we also discover substantial variation: the majority of default studies find positive effects, but several do not find a significant effect, and two even demonstrate negative effects. To explain this variability, we draw on existing theoretical frameworks to examine the drivers of disparity in effectiveness. Our analysis reveals two factors that partially account for the variability in defaults’ effectiveness. First, we find that defaults in consumer domains are more effective and in environmental domains are less effective. Second, we find that defaults are more effective when they operate through endorsement (defaults that are seen as conveying what the choice architect thinks the decision-maker should do) or endowment (defaults that are seen as reflecting the status quo). We end with a discussion of possible directions for a future research program on defaults, including potential additional moderators, and implications for policy-makers interested in the implementation and evaluation of defaults.

Why are some nudges ineffective, or at least less effective than choice architects hope and expect? Focusing primarily on default rules, this essay emphasizes two reasons for this. The first involves strong antecedent preferences on the part of choosers. The second involves successful “counternudges,” which persuade people to choose in a way that confounds the efforts of choice architects. Nudges might also be ineffective, and less effective than expected, for five other reasons: (1) some nudges produce confusion in the target audience; (2) some nudges have only short-term effects; (3) some nudges produce “reactance” (though this appears to be rare); (4) some nudges are based on an inaccurate (though initially plausible) understanding on the part of choice architects of what kinds of choice architecture will move people in particular contexts; and (5) some nudges produce compensating behavior, resulting in no net effect. When a nudge turns out to be insufficiently effective, choice architects have three potential responses: (1) do nothing; (2) nudge better (or differently); and (3) fortify the effects of the nudge, perhaps through counter-counternudges, or perhaps through incentives, mandates, or bans.

Conventional economic policy focuses on ‘economic’ solutions (e.g. taxes, incentives, regulation) to problems caused by market-level factors such as externalities, misaligned incentives and information asymmetries. By contrast, ‘nudges’ provide behavioural solutions to problems that have generally been assumed to originate from limitations in human decision making, such as present bias. While policy-makers have good reason for exploiting the power of nudges, we argue that these extremes leave open a large space of policy options that have received less attention in the academic literature. First, there is no reason that solution and problem need have the same theoretical basis: there are promising behavioural solutions to problems that have causes that are well explained by traditional economics, and conventional economic solutions often offer the best line of attack on problems of behavioural origin. Second, there is a wide range of hybrid policy actions with both economic and behavioural components (e.g. framing a tax or incentive in a specific way), and there exist many societal problems – perhaps the majority – that arise from both economic and behavioural factors (e.g. firms’ exploitation of consumers’ behavioural biases). This paper aims to remind policy-makers that behavioural economics can influence policy in a variety of ways, of which nudges are the most prominent but not necessarily the most powerful.

In this article, we lay out the basic case for wellbeing as the goal of government. We briefly review the history of this idea, which goes back to the ancient Greeks and was the acknowledged ideal of the Enlightenment. We then discuss possible measures on which a wellbeing orientation could be based, emphasizing the importance of acknowledging the political agency of citizens and thus their own evaluations of their lives. We then turn to practicalities and consequences: how would one actually set up wellbeing-oriented decision-making and what difference should we expect from current practice? We end by discussing the current barriers to the adoption of wellbeing as the goal of government, both in terms of what we need to know more about and where the ideological barriers lie.

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.

In recent years, public officials have shown a growing interest in using evidence from the behavioural sciences to promote policy goals. Much of the discussion of behaviourally informed approaches has focused on ‘nudges’; that is, non-fiscal and non-regulatory interventions that steer (nudge) people in a specific direction while preserving choice. Less attention has been paid to boosts, an alternative evidence-based class of non-fiscal and non-regulatory intervention. The goal of boosts is to make it easier for people to exercise their own agency in making choices. For instance, when people are at risk of making poor health, medical or financial choices, the policy-maker – rather than steering behaviour through nudging – can take action to foster or boost individuals’ own decision-making competences. Boosts range from interventions that require little time and cognitive effort on the individual's part to ones that require substantial amounts of training, effort and motivation. This article outlines six rules that policy-makers can apply in order to determine under which conditions boosts, relative to nudges, are the preferable form of non-fiscal and non-regulatory intervention. The objective is not to argue that boosts are better than nudges or vice versa, but to begin to spell out the two approaches’ respective conditions for success.

Counter to the traditional assumption of neoclassical economics that individuals are rational Homo oeconomici that always seek to maximize their utility and follow their ‘true’ preferences, research in behavioural economics has demonstrated that people's judgements and decisions are often subject to systematic biases and heuristics, and are strongly dependent on the context of the decision. In this article, we briefly review the transition of research from neoclassical economics to behavioural economics, and discuss how the latter has influenced research in consumer behaviour and consumer policy. In particular, we discuss the impacts of key principles such as status quo bias, the endowment effect, mental accounting and the sunk-cost effect, other heuristics and biases related to availability, salience, the anchoring effect and simplicity rules, as well as the effects of other supposedly irrelevant factors such as music, temperature and physical markers on consumers’ decisions. These principles not only add significantly to research on consumer behaviour – they also offer readily available practical implications for consumer policy to nudge behaviour in beneficial directions in consumption domains including financial decision making, product choice, healthy eating and sustainable consumption.

Consumers, employees, students and others are often subjected to ‘sludge’: excessive or unjustified frictions, such as paperwork burdens, that cost time or money; that may make life difficult to navigate; that may be frustrating, stigmatizing or humiliating; and that might end up depriving people of access to important goods, opportunities and services. Because of behavioral biases and cognitive scarcity, sludge can have much more harmful effects than private and public institutions anticipate. To protect consumers, investors, employees and others, firms and private and public institutions should regularly conduct Sludge Audits to catalogue the costs of sludge and to decide when and how to reduce it. Sludge often has costs far in excess of benefits, and it can hurt the most vulnerable members of society.

We argue that the behavioral challenges posed by climate change are fundamentally problems of social influence. Behaviors that perpetuate climate change are often opaque in their consequences; thus, we look to others to infer how to act. Yet unsustainable behaviors, like driving and eating meat, are often the norm; conformity to such norms is a major hurdle to a more sustainable world. Nonetheless, we argue that social norms can also be a powerful lever for positive change. Drawing on two streams of recent research, we show that well-implemented social norm strategies can motivate positive steps even in the face of a negative current norm and even in individuals’ private behavior absent the judgment of others. First, appeals to dynamic norms – information about change in others or trends in norms over time – can lead people to conform to the change itself, even if this change violates current norms. Second, framing normative appeals in terms of an invitation to work with others toward a common goal can increase the motivation to join in. Despite ubiquitous unsustainable norms, careful theory-based representations of social norms can help us make progress on climate change.

Reducing global warming will require enacting strong climate policies, which is unlikely to happen without public support. While prior research has identified varied predictors of climate change policy support, it is unclear which predictors are strongest for the American electorate as a whole, and which predictors are strongest for Democrats and Republicans. In a nationally representative sample of registered voters (n = 2063), we use relative weight analysis to identify the strongest predictors of public climate policy support. We find that, among registered voters in the USA, the five most important predictors of climate policy support are: worry about global warming; risk perceptions; certainty that global warming is happening; belief that global warming is human-caused; and general affect toward global warming. Collectively, these five variables account for 51% of the variance in policy support. Results split by political party indicate that pro-climate injunctive norms and global warming risk perceptions are the variables that differ most between Republicans and Democrats, accounting for significantly more variance in policy support among Republicans. These findings can inform policymakers and advocates seeking to build public support for climate action.

A criticism of behavioural nudges is that they lack precision, sometimes nudging people who – had their personal circumstances been known – would have benefitted from being nudged differently. This problem may be solved through a programme of personalized nudging. This paper proposes a two-component framework for personalization that suggests choice architects can personalize both the choices being nudged towards (choice personalization) and the method of nudging itself (delivery personalization). To do so, choice architects will require access to heterogeneous data. This paper argues that such data need not take the form of big data, but agrees with previous authors that the opportunities to personalize nudges increase as data become more accessible. Finally, this paper considers two challenges that a personalized nudging programme must consider, namely the risk personalization poses to the universality of laws, regulation and social experiences, and the data access challenges policy-makers may encounter.

Nudge plus is a modification of the toolkit of behavioral public policy. It incorporates an element of reflection – the plus – into the delivery of a nudge, either blended in or made proximate. Nudge plus builds on recent work combining heuristics and deliberation. It may be used to design prosocial interventions that help preserve the autonomy of the agent. The argument turns on seminal work on dual systems, which presents a subtler relationship between fast and slow thinking than commonly assumed in the classic literature in behavioral public policy. We review classic and recent work on dual processes to show that a hybrid is more plausible than the default-interventionist or parallel-competitive framework. We define nudge plus, set out what reflection could entail, provide examples, outline causal mechanisms, and draw testable implications.

This article argues that nudges can often be turned into self-nudges: empowering interventions that enable people to design and structure their own decision environments – that is, to act as citizen choice architects. Self-nudging applies insights from behavioral science in a way that is practicable and cost-effective, but that sidesteps concerns about paternalism or manipulation. It has the potential to expand the scope of application of behavioral insights from the public to the personal sphere (e.g., homes, offices, families). It is a tool for reducing failures of self-control and enhancing personal autonomy; specifically, self-nudging can mean designing one's proximate choice architecture to alleviate the effects of self-control problems, engaging in education to understand the nature and causes of self-control problems and employing simple educational nudges to improve goal attainment in various domains. It can even mean self-paternalistic interventions such as winnowing down one's choice set by, for instance, removing options. Policy-makers could promote self-nudging by sharing knowledge about nudges and how they work. The ultimate goal of the self-nudging approach is to enable citizen choice architects’ efficient self-governance, where reasonable, and the self-determined arbitration of conflicts between their mutually exclusive goals and preferences.

Widespread testing is key to controlling the spread of COVID-19. But should we worry about self-selection bias in the testing? The recent literature on willful ignorance says we should – people often avoid health information. In the context of COVID-19, such willful ignorance can bias testing data. Furthermore, willful ignorance often arises when selfish wants conflict with social benefits, which might be particularly likely for potential ‘super-spreaders’ – people with many social interactions – given people who test positive are urged to self-isolate for two weeks. We design a survey in which participants (n = 897) choose whether to take a costless COVID-19 test. We find that 70% would take a test. Surprisingly, the people most likely to widely spread COVID-19 – the extraverts, others who meet more people in their daily lives and younger people – are the most willing to take a test. People's ability to financially or emotionally sustain self-isolation does not matter to their decision. We conclude that people are selfless in their decision to test for COVID-19. Our results are encouraging – they imply that COVOD-19 testing may succeed in targeting those who generate the largest social benefits from self-isolation if infected, which strengthens the case for widespread testing.

Nudging is considered a promising approach for behavioural change. At the same time, nudging has raised ethical concerns, specifically in relation to the impact of nudges on autonomous choice. A complexity is that in this debate authors may appeal to different understandings or dimensions of autonomy. Clarifying the different conceptualisations of autonomy in ethical debates around nudging would help to advance our understanding of the ethics of nudging. A literature review of these considerations was conducted in order to identify and differentiate between the conceptualisations of autonomy. In 33 articles on the ethics of nudging, we identified 280 autonomy considerations, which we labelled with 790 unique autonomy codes and grouped under 61 unique super-codes. Finally, we formulated three general conceptualisations of autonomy. Freedom of choice refers to the availability of options and the environment in which individuals have to make choices. Agency involves an individual's capacity to deliberate and determine what to choose. Self-constitution relates to someone's identity and self-chosen goals. In the debate about the ethics of nudging, authors refer to different senses of autonomy. Clarifying these conceptualisations contributes to a better understanding of how nudges can undermine or, on the other hand, strengthen autonomy.

Limits on consumer attention give firms incentives to manipulate prospective buyers’ allocation of attention. This paper models such attention manipulation and shows that it limits the ability of disclosure regulation to improve consumer welfare. Competitive information supply from firms competing for attention can reduce consumers’ knowledge by causing information overload. A single firm subjected to a disclosure mandate may deliberately induce such information overload to obfuscate financially relevant information or engage in product complexification to bound consumers’ financial literacy. Thus, disclosure rules that would improve welfare for agents without attention limitations can prove ineffective for consumers with limited attention. Obfuscation suggests a role for rules that mandate not only the content, but also the format of disclosure; however, even rules that mandate ‘easy-to-understand’ formats can be ineffective against complexification, which may call for regulation of product design.

‘Nudge’ is a concept of policy intervention that originates in Thaler and Sunstein's (2008) popular eponymous book. Following their own hints, we distinguish three properties of nudge interventions: they redirect individual choices by only slightly altering choice conditions (here ‘nudge 1’); they use rationality failures instrumentally (here ‘nudge 2’); and they alleviate the unfavourable effects of these failures (here ‘nudge 3’). We explore each property in semantic detail and show that no entailment relation holds between them. This calls into question the theoretical unity of nudge as intended by Thaler and Sunstein and most of their followers. We eventually recommend pursuing each property separately, both in policy research and at the foundational level. We particularly emphasise the need for reconsidering the respective roles of decision theory and behavioural economics to delineate nudge 2 correctly. The paper differs from most in the literature in focusing on the definitional rather than the normative problems of nudge.

What are the roles of bottom-up and top-down signals in the formation of climate change policy preferences? Using a large sample of American residents (n = 1520) and combining an experimental manipulation of descriptive social norms with two choice experiments, we investigate the effects of descriptive norms and policy endorsements by key political actors on climate policy support. We study these questions in two areas considered to be central in a number of decarbonization pathways: the phase-out of fossil fuel-powered cars and the deployment of carbon capture and storage. Our study provides two important results. First, social norm interventions may be no silver bullet for increasing citizens’ support for ambitious climate policies. In fact, we not only find that climate policy support is unaffected by norm messages communicating an increased diffusion of pro-environmental behaviors, but also that norm messages communicating the prevalence of non-sustainable behaviors decrease policy support. Second, in the presence of policy endorsements by political parties, citizens’ trust in these parties influences their support for climate policies. This study contributes to research in behavioral climate policy by examining the impact of descriptive norms and elite cues on climate policy support.