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Rethinking public health using behavioural science

Attempts to persuade people to be healthier often have limited success. Public health should focus more on marginal gains that require little or no effort, says Michael Hallsworth.

Most of the burden of disease in developed countries is created by what people eat, drink, or smoke. Influencing behaviour has therefore emerged as a key challenge for policymakers and public health professionals. To meet this challenge, much public health policy has focused on influencing beliefs and attitudes: providing people with information about the risks and benefits of behaviours, then asking them to make a deliberate effort to change.

Despite some successes, the impact of this attitude-based approach has often been limited. Decades of behavioural science research helps to explain why: our decisions are more habitual, automatic, and influenced by the immediate environment than traditional public health approaches have assumed. As a result, informing and encouraging people to deliberately make a healthy choice might not lead to improved health.

One implication of this research is that public health should focus more on approaches that require very little or no effort, given that humans are effort minimizers. The general move here is away from persuading people to engage in a conscious and effortful conversion to achieve an ideal target behaviour, and towards offering them easy and realistic ways to switch to a marginally healthier option. What’s surprising is how controversial this shift can be in practice.

Take electronic cigarettes, for example. Since they function like tobacco cigarettes, they require smokers to make less effort to disrupt existing habits than most other nicotine replacement products. They can, therefore, reach people who are unable to quit using more effortful means, even though they want to. Studies on the growth of e-cigarettes show that this is what has happened — they have, in the UK, become the most popular route to quitting smoking. However, it is plausible that this advantage — their similarity to cigarettes — has also triggered opposition within the public health community. Evidence from the behavioural sciences shows that many of our decisions are made quickly and instinctively using mental shortcuts or ‘heuristics’. Many public health professionals may have simply applied the heuristic of ‘anything that looks like smoking must be opposed’, informed by long practice of — rightly — opposing the tobacco industry. Given the evidence available, much public health opposition to e-cigarettes can be interpreted as attempts to post-rationalize this instinctive dislike.

Public health should focus more on approaches that require very little or no effort

Of course, e-cigarettes are not harm-free, and we urgently need research to establish those harms. Ideally, it would be better if people quit nicotine altogether. But if we had a stronger focus on the importance of effort minimization — and the fact that the harms are clearly much lower than from cigarettes — then this would counterbalance the similarity-to-smoking heuristic, and allow a more reasoned and evidenced debate. As it is, the confusion that has been created over the relative harms of e-cigarettes may be costing lives.

Diet and obesity is another area where we need to focus more on achieving marginal shifts in behaviour. Sometimes people are only willing to shift to slightly healthier products, and some change is better than no change. But the effects of cumulative marginal changes can be more important than we tend to realize. One reason is that the energy imbalance that leads to obesity is often relatively small (50–100 calories a day), but repeated over time. Repeated marginal changes might be enough to close this gap. Perhaps even more importantly, wider changes in the food system can result from these marginal shifts: food producers and retailers will have an incentive to develop, stock and promote healthier versions of similar foods, effectively competing for these marginal choices. Over time, changes in food reformulation and what stores stock mean that the health benefits will reach even those who have not changed their behaviour at all.

Regulation seems to offer a more direct route to improve the nutritional content of foods or to control access to cigarettes. Regulation has improved the public’s health greatly over the years. But policymakers often struggle to directly control the behaviour of markets, which are complex adaptive systems filled with actors who usually have an incentive to evade regulations. Regulation did not manage to create a well-functioning nicotine replacement market, for example. Therefore public health policy could achieve greater success if it also adopts a more sophisticated understanding of how to gear market behaviour towards improving health. Regulation should be part of the policy mix, but injunctions alone fail to use the power of the market to improve health, meaning opportunities are being missed.

The problem is that these approaches sit uncomfortably with many existing practices and attitudes. Opportunities are indeed being missed if we aim only for people to do the right thing for the right reason, rather than for convenience, variety or indifference. The public health community might achieve its goals better by adopting indirect approaches that make shifts towards healthier options easier, rather than focusing solely on overt attempts to convert people to an ideal behaviour. Paradoxically, persuasion might not be persuasive.

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Correspondence to Michael Hallsworth.

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Hallsworth, M. Rethinking public health using behavioural science. Nat Hum Behav 1, 612 (2017). https://doi.org/10.1038/s41562-017-0188-0

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