IN 2013 thousands of school pupils in England received a letter from a student named Ben at the University of Bristol. The recipients had just gained good marks in their GCSEs, exams normally taken at age 16. But they attended schools where few pupils progressed to university at age 18, and those that did were likely to go to their nearest one. That suggested the schools were poor at nurturing aspiration. In his letter Ben explained that employers cared about the reputation of the university a job applicant has attended. He pointed out that top universities can be a cheaper option for poorer pupils, because they give more financial aid. He added that he had not known these facts at the recipient’s age.

The letters had the effect that was hoped for. A study published in March found that after leaving school, the students who received both Ben’s letter and another, similar one some months later were more likely to be at a prestigious university than those who received just one of the letters, and more likely again than those who received none. For each extra student in a better university, the initiative cost just £45 ($58), much less than universities’ own attempts to broaden their intake. And the approach was less heavy-handed than imposing quotas for poorer pupils, an option previous governments had considered. The education department is considering rolling out the scheme.

The trial was run by the Behavioural Insights Team (BIT), a company spun out of the British government in 2014 and which remains in part publicly owned. BIT has pioneered the use of psychology to help policymakers change behaviour through “nudges” rather than taxes or laws. That approach is spreading, as governments from Australia to Qatar, and bodies such as the UN and World Bank, follow.

Mind over matter

When BIT was set up, in 2010, the very idea provoked objections. Some critics feared that nudges would do little good, and that their effects would fade over time. Others warned that governments were straying perilously close to mass manipulation. More recently, some of the findings on which the behavioural sciences rest have been questioned, as researchers in many fields have sought to replicate famous results, and failed.

By and large those doubts have been allayed. Even if specific results turn out to be mistaken, an experimental, iterative, data-driven approach to policymaking is gaining ground in many places, not just in dedicated units, but throughout government.

Nudging is hardly new. “In Genesis, Satan nudged, and Eve did too,” writes Cass Sunstein of Harvard University. From the middle of the 20th century psychologists such as Stanley Milgram and Philip Zimbardo showed how sensitive humans are to social pressure. Daniel Kahneman and Amos Tversky described the mental shortcuts and biases that influence decision-making. Dale Carnegie and Robert Cialdini wrote popular books on persuasion. Firms, especially in technology, retail and advertising, used behavioural science to shape brand perception and customer behaviour—and, ultimately, to sell more stuff.

But governments’ use of psychological insights to achieve policy goals was occasional and unsystematic. According to David Halpern, the boss of BIT, as far as policymakers were concerned, psychology was “the sickly sibling to economics”. That began to change after Mr Sunstein and Richard Thaler, an economist, published “Nudge”, in 2008. The book attacked the assumption of rational decision-making inherent in most economic models and showed how “choice architecture”, or context, could be changed to “nudge” people to make better choices.

In 2009 Barack Obama appointed Mr Sunstein as head of the White House’s Office of Information and Regulatory Affairs. The following year Mr Thaler advised Britain’s government when it established BIT, which quickly became known as the “nudge unit”. If BIT did not save the government at least ten times its running cost (£500,000 a year), it was to be shut down after two years.

Not only did BIT stay open, saving about 20 times its running cost, but it marked the start of a global trend. Now many governments are turning to nudges to save money and do better. In 2014 the White House opened the Social and Behavioural Sciences Team. A report that year by Mark Whitehead of Aberystwyth University counted 51 countries in which “centrally directed policy initiatives” were influenced by behavioural sciences. Non-profit organisations such as Ideas42, set up in 2008 at Harvard University, help run dozens of nudge-style trials and programmes around the world. In 2015 the World Bank set up a group that is now applying behavioural sciences in 52 poor countries. The UN is turning to nudging to help hit the “sustainable development goals”, a list of targets it has set for 2030.

Not all these schemes involve a dedicated nudge unit. Many draw on initiatives that predate BIT. But all use similar insights from behavioural psychology to design and test policy tweaks. These are summed up in EAST, a mnemonic devised by BIT: in order to change behaviour, make good choices easy, attractive, social and timely.

Heading EAST

One of the best-known nudges is to set the desired outcome as the default. For example, enrolling all workers in a company pension scheme, and requiring them to opt out if they do not wish to be members, greatly increases savings rates compared with when non-membership is the default. The power of making things easy was also demonstrated by a trial in 2012, in which the forms used by poor Americans to apply to university were pre-filled with data from tax returns. That raised the likelihood that they would go to university by a quarter. Nudges that involve making the desired choice more attractive, or at least more obvious, range from making the wording on letters about late payment of taxes more emphatic to placing healthy food at eye level in canteens.

Among the most effective nudges are “social” ones: those that communicate norms or draw on people’s networks. A scheme tested in Guatemala with help from the World Bank and BIT tweaked the wording of letters sent to people and firms who had failed to submit tax returns the previous year. The letters that framed non-payment as an active choice, or noted that paying up is more common than evasion, cut the number of non-payers in the following year and increased the average sum paid. And a trial involving diabetes shows that it matters to nudge at the right moment. In 2014 Hamad Medical Corporation, a health-care provider in Qatar, raised take-up rates for diabetes screening by offering it during Ramadan. That meant most Qataris were fasting, so the need to do so before the test imposed no extra burden.

Owain Service, BIT’s managing director, says it was initially accused of “tinkering at the margins”. But nudging is now being brought to bear on bigger, harder, problems. One is making public bodies more representative of those they serve. American police forces have long struggled to recruit from ethnic minorities; many worry that their failure to do so harms community relations and makes it tougher for officers to do their job. Many attempts have been made to improve matters, without much success. But BIT’s North America team helped the police force in Chattanooga, Tennessee, to test various versions of job ads. Those emphasising the challenge of the job or the career benefits attracted many more black and Hispanic applicants than those emphasising the impact of the work on the community or the opportunity to serve.

Of particular interest in aid and development are recent efforts to use nudges to tackle corruption. The World Bank has been involved in several trials, for example one in Nigeria to improve record-keeping in health clinics, thereby making it less likely that money will be stolen. It has found that giving health workers who keep good records certificates that they can display in their clinics makes a worthwhile difference. Another promising area involves motivating people to refuse bribes. Anti-corruption policies generally rely on punishment. But behavioural insights suggest harnessing social norms, for example by publicly celebrating those who stay clean.

Far from being fleeting, as had been feared, at least some nudges have been shown to form lasting habits. Todd Rogers of Harvard University found that asking prospective voters just once to note down exactly when they were going to vote not only increased turnout in an imminent election, but also in subsequent ones. The Guatemalans who received the letters that worked best to encourage taxpaying the following year turned out to be more likely to pay up the year after, too.

Technology is increasing the impact of behavioural techniques. Several British departments employ data scientists who can run speedy trials of letters and leaflets, much as media companies learn what works online by “A/B testing” content, serving one version to half their audience and another to the rest to see which one is more viewed, liked and shared.

Brain gain

Many of the early critics of nudge techniques regarded them as infantilising, or even a type of government mind control. “Nanny is alive and well in Westminster” ran the headline of a newspaper article about the nudge unit in 2011; the author went on to deride the unit’s “Orwellian overtones”. Many worried about the idea of bureaucrats being given free rein to shape behaviour by imperceptibly tweaking government communications and environmental cues.

Even the proponents acknowledge the risks. “Hitler nudged, so did Stalin,” writes Mr Sunstein. Laws in some American states that have suppressed black people’s votes, such as those passed by North Carolina in 2013, look remarkably like nefarious nudges, from limiting the types of IDs that can be used for registration to banning out-of-precinct voting. All made voting less easy, attractive, social and timely—and disproportionately cut the number of black people voting.

North Carolina’s laws were struck down on appeal last year, in a nice demonstration of the need for checks and balances when it comes to nudging, as with all other policy action. And all governments nudge whether they have a dedicated unit for doing it, Mr Sunstein points out, and whether or not they mean to. There is no purely neutral way of presenting choices, so why not try to choose the one that results in the best outcomes? As long as that choice is made in a transparent manner, and is subject to democratically elected politicians, nudging offers policymakers an alternative to both the nanny state and the unintelligent one; a middle way that he describes as “libertarian paternalism”.

A “replication crisis”, in which scientists in many fields have repeated published experiments and failed to find the same results, has hit particularly hard in the behavioural sciences, with some much-cited findings now open to question. But the approach taken by nudge units and their kind already incorporates the remedy. It has nudged policymakers towards a new way of thinking about policy that involves trial and error, and step-by-step improvement. The theories of behavioural science can only suggest which nudges to try; it is for policymakers to find out which ones work.