Intended for healthcare professionals


One nudge forward, two steps back

BMJ 2011; 342 doi: (Published 25 January 2011) Cite this as: BMJ 2011;342:d401
  1. Chris Bonell, senior lecturer in social science and epidemiology,
  2. Martin McKee, professor of European public health,
  3. Adam Fletcher, lecturer in sociology and social policy,
  4. Paul Wilkinson, reader in environmental epidemiology,
  5. Andy Haines, professor of public health and primary care
  1. 1Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London WC1H 9SH, UK
  1. chris.bonell{at}

Why nudging might make for muddled public health and wasted resources

In the linked article (doi:10.1136/bmj.d228), Marteau and colleagues offer a timely note of caution about “nudging”—an approach to behaviour change described in Nudge: Improving Decisions about Health, Wealth and Happiness, a book by the US academics Richard Thaler and Cass Sunstein—which is the coalition government’s preferred strategy for promoting public health.1

Based on an explicitly self contradictory concept termed “libertarian paternalism,”2 nudging recognises that our everyday decisions are often not conscious and rational. Much of our behaviour is automatic or follows perceived norms, and it relies on poor information about consequences or overinterpretation of misleading information. Consequently, nudging is based on the principle that it is legitimate to influence people’s behaviour to make their lives healthier (paternalism), but that such influence should be unobtrusive and not entail compulsion (libertarian). Nudges might involve subconscious cues (such as painting targets in urinals to improve accuracy) or correcting misapprehensions about social norms (like telling us that most people do not drink excessively). They can alter the profile of different choices (such as the prominence of healthy food in canteens) or change which options are the default (such as having to opt out of rather than into organ donor schemes). Nudges can also create incentives for some choices or impose minor economic or cognitive costs on other options (such as people who quit smoking banking money they would have spent on their habit but only being able to withdraw it when they test as nicotine free).

As Marteau and colleagues note, despite the fanfares with which nudging has been presented in the recent public health white paper Healthy Lives, Healthy People, these ideas are far from new. Supermarkets have spent enormous sums on research into how to direct our choices in ways that serve what they define as our interests (in other words, their own), most obviously by lining check-out queues with sweets placed at children’s eye level.3 Meanwhile, concepts such as social norms and incentivisation are rooted in longstanding theories of health behaviour. Marteau and colleagues rightly point out the vagueness with which the term nudge has been used, its limited evidence base, and its potential for harm. They call for new primary research and systematic reviews to examine the effectiveness of public health nudges.

However, we shouldn’t rush into investigating the evidence base of nudging unless it offers something that existing approaches do not. Defined negatively, nudges seem to be anything other than just giving people basic factual information to enable them to make more rational, conscious decisions, or compelling them to change behaviour. It isn’t clear how nudges are distinctive in any other way. Public health is rarely coercive (other than to prevent harm to third parties), generally goes beyond information giving, and already seeks to influence how choices are presented. For example, social marketing engages with emotional decision making using techniques borrowed from advertising.4 Motivational interviewing draws on people’s need for cognitive consistency, and it helps people to identify disparities between their goals and current behaviours, with the aim of changing any disparate behaviours.5 Peer education harnesses the power of social norms by enabling people to spread health messages through their social networks.6 Structural interventions modify the physical, organisational, or social environment to change behaviour.7

Unlike nudging, all of these existing approaches are informed by theories that help define which interventions qualify as examples and identify the causal pathways along which they aim to operate. More research is certainly needed, but it should be focused on approaches with a clear theoretical basis and a coherent causal pathway linking the intervention to the desired outcome.

Furthermore, many of Thaler and Sunstein’s examples of nudges don’t fit with their own definition. They cite legislation mandating cigarette packets to present information on the risks of smoking, an example of using basic factual information to promote behaviour change in a way that nudging is supposed to transcend. They also cite a programme paying a “dollar a day” to teenage mothers contingent on their having no further pregnancies; this would exert a considerable financial pressure on young women in poverty, contradicting the definition of nudges as not exerting such pressures.

Nudge is an interesting book, but for its politics not its science. In describing nudging as libertarian paternalism, it makes a strong case for state action in the context of contemporary America, where large numbers of citizens have been influenced by a media shaped by corporate interests to vote against governmental measures that would benefit them.8 Thaler and Sunstein argue for the legitimacy of state intervention to benefit citizens as long as it neither hectors nor coerces (but they acknowledge in their conclusions that there are no hard and fast cut-off points). Although persuasive, their argument rests on attacking a straw man. As argued above, most public health is not coercive (and goes beyond information giving); this is also surely true of most other social policies, aside from the compulsion to attend school and pay taxes.

In terms of public health science, the notion of nudging adds nothing to existing approaches. Public health policies should be based on the best available evidence, but the government has shown a worrying tendency to undermine the collection of such evidence—for example, by stopping the National Institute for Health and Clinical Excellence from undertaking appraisals of several strategies to improve public health.9 Nudge contains some eye catching ideas, but little progress will be made if public health policy is made largely on the basis of ideology and ill defined notions that fail to deal with the range of barriers to healthy living.


Cite this as: BMJ 2011;342:d401


  • Analysis, doi:10.1136/bmj.d228
  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work (other than the institution receiving several research grants from the Department of Health and the National Institute for Health Research) in the previous three years, no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Commissioned; not externally peer reviewed.


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