With an estimated 5,000 to 10,000 coronavirus cases now present in the UK, the government has eschewed social distancing measures such as closing schools and banning large sporting events. Instead, it has opted for behavioural “nudges”: wash your hands, don’t touch your face, don’t shake hands with others, stay at home if you feel ill, and self-isolate if you have a continuous cough. This approach differs starkly from the quarantine measures taken in China, South Korea, Italy and Iran. But it also marks the UK out as different from countries such as Ireland, Norway and Denmark, which have implemented school closures despite seeing only a relatively small number of coronavirus cases. Patrick Vallance, the government’s chief scientific adviser, has explained that part of the reason for not embracing bans is to encourage “herd immunity”. Allow enough of those who can survive coronavirus disease to get infected, and the virus won’t have new people to infect, meaning new cases will dry up. Other European countries seem to have judged this too bold an approach. Immunity will probably be temporary, so later outbreaks are to be expected, and dealt with by heightened contact tracing when they occur. The UK government’s strategy is influenced by nudge theory, an idea first popularised by the behavioural economist Richard Thaler and political scientist Cass Sunstein. “Nudging” uses insights about our mental processes to change our behaviour through coaxing and positive assertion. Rather than forcing us to do things, nudging tweaks the environments in which we make choices – for example by requiring people to opt out of organ donation, rather than opting in. Perhaps most importantly of all, nudge thinking has informed what the UK is not doing. As stressed by the government and David Halpern, leader of the behavioural insights team (aka the “nudge unit”) that is playing a big role in advising the government’s response, the reason that it isn’t yet time to close schools or ban large gatherings is that “fatigue” could set in – meaning people will grow tired of the bans and find ways around them. If the effectiveness of social distancing measures is time-limited, the logic seems to be, better to reserve these measures for when we’re closer to the peak of the epidemic The government’s press conference on Thursday featured other more subtle nudges too. Boris Johnson was flanked and followed by his scientific advisers, a visual reinforcement of the message that the government is trusting the science – and knows what it’s doing. But the UK’s strategy is an outlier. If the nudgers have got it right, why are so many other countries taking a very different view of the “science”? The predictions about fatigue setting in, on the face of it, seem dubious. We might get tired of bans on large gatherings such as gigs, concerts and sporting events, or school closures, but we can’t circumvent them; and nothing we might do has the same capacity for “super-spreading” the virus to large numbers at once. And if we are prone to fatigue, why rely on the one thing we can ignore – advice about hand washing? The government’s strategy has at its heart predictions about human behaviour. Predictions are based on analysing past episodes of human behaviour, a process that is often fraught with error, to draw inferences about future behaviour, which can be highly uncertain. Which analyses of human behaviour are government scientists relying on? And how comparable are they? Why is fatigue such a problem for new coronavirus measures, which we might expect would command the same kind of support as a war effort, when the state lives with this “fatigue” in the design of the laws and norms that permanently regulate our lives? We can’t answer these questions, because the government’s scientists aren’t yet disclosing what studies and past evidence underpin their current approach. The government’s tactic – one might even call it a nudge – is to appeal to the credentials of its advisers and behavioural scientists, and to trust the experts. Halpern’s behavioural insights team, which was created in 2010 by the coalition government as a company part-owned by the UK Cabinet Office, counts some successes – including encouraging more black and minority ethnic police recruits and coaxing high earners to pay more tax. And there are weightier pieces of evidence in the epidemiology literature to suggest that fatigue is a genuine problem – for example, research shows that media messages about flu have a diminishing effect on human behaviour. But we can’t tell what role studies like this are playing in government thinking, and such studies lead us back to the same conundrum: if we are prone to fatigue, why rely on nudges, and why delay less easily disregarded and legalised social distancing? The approaches in the UK and the rest of Europe are starkly different, and both cannot be right. Mistakes by one country are going to spill over into outcomes for another. Nowhere will this be more clear than in Ireland: north of the Irish border, UK schools are open and citizens are being nudged in the fashion of “keep calm and wash your hands”. South of the border, schools are closed – and nudges aren’t considered a sufficient response. The Vote Leave campaign that Johnson led implored us to ignore the economic consensus about the likely effects of Brexit. The government he is leading now is reversing course and imploring us to listen to the experts – in this case, experts on behavioural science. We might be nudged further towards heeding the advice of Johnson and his team were their evidence base for Britain’s divergent coronavirus response shared with the public. • Tony Yates is a former professor of economics at Birmingham University. He is an adviser at Resolution Foundation and Fathom Consulting