1 February 2023

Nudge, nudge – who’s there?

By Frances An

Ever since Richard Thaler and Cass Sunstein published Nudge in 2008, the theory that bears the same name has been all the rage.

Briefly put, ‘nudge theory’ is the idea that small adjustments in the environment (‘nudges’) can influence people’s behaviour, often beyond conscious awareness. A simple example Thaler gives is putting healthy foods in a more prominent position in a supermarket to encourage better diet choices.

Thaler and Sunstein call the ideology that underpins their theory ‘libertarian paternalism’, a somewhat oxymoronic label that denotes ‘an approach that preserves freedom of choice but that authorises both private and public institutions to steer people in directions that will promote their welfare’.

The pair’s ideas found their way into government here in the UK when David Cameron’s coalition government established the Behavioural Insights Team – widely known as the Nudge Unit – back in 2010. Where the UK led, others followed, and there are now Nudge Unit equivalents in hundreds of other countries.

The UK version is no longer part of the Government, having been hived off to the charity Nesta. Nonetheless, its chairman David Halpern created a bit of controversy recently when he claimed to have personally ‘nudged’ Boris Johnson into wearing a mask during the pandemic.

It is just that kind of apparent subliminal manipulation that has raised concerns about the ethical application of nudge theory. Indeed, BIT co-founder Simon Ruda has written of his fears about the ‘propagandistic’ use of behavioural science during the pandemic and ‘the level of fear willingly conveyed on the public’. Though Ruda remains a firm supporter of driving prosocial behaviours such as tax compliance or healthy eating, he also has serious concerns about ‘the creeping acceptance among policy makers that the state should use its heft to influence our lives without the accountability of legislative and parliamentary scrutiny’.

Prior to Covid, nudge theory had primarily been seen as a way of prompting people in pretty benign ways, improving outcomes in areas like public space planning, alcohol policy and education. Indeed, you could see all the hallmarks of nudge theory when Congress recently passed Secure 2.0, a series of provision changes which include a requirement for employers’ to automatically enrol employees in retirement plans, rather than requiring employees to manually opt in.

What’s striking, however, is that for all the excitement and moral panic about the power of nudge theory, empirical evidence for its effectiveness has always been fairly shaky.

To explain why, it’s worth going back to its origins. At its core, nudge theory is an ideologically recalibrated version of the ‘subliminal influence’ concept from psychophysics, a sub-discipline of psychology that studies the processing of physical stimuli into human perception. Psychophysics experiments on sensory thresholds often involve presenting a stimulus (e.g. a flashing image or audio tone) multiple times and asking participants to indicate when they detected it. The stimulus is deemed ‘subliminal’ if participants detect it less than 50% of the time. Subliminal influence, therefore, is when people’s behaviour changes according to subliminally presented stimuli.

Much like nudge theory, subliminal influence generated an ethical storm after James Vicary’s 1957 market research study, in which he claimed to be able to boost sales of popcorn and Coke by flashing the words ‘eat popcorn’ and ‘drink Coca-Cola’ during a movie. That such a thing appeared possible only intensified Red Scare era fears that communists might be able to achieve nefarious ideological aims using the same techniques. Vance Packard’s best-selling book The Hidden Persuaders, published in the same year as Vicary’s study, embodied the paranoia of the age about powerful actors using underhand techniques to influence the public.

The only problem was, Vicary’s results were bogus. The manager of the cinema in question said Vicary’s flashing words had had no impact on sales, and Vicary himself admitted his research should never have been made public. Unsurprisingly, his results have not been replicated since, including in an experiment organised by the BBC in 2015 that attempted to influence participants into drinking Lipton by subliminally flashing ‘Lipton’ during a three-minute drama clip.

But whether we call it nudge theory or subliminal influence, the evidence that manipulating people through subconsciously targeted gimmicks remains weak. University of Cambridge researcher Magda Osman eloquently set out some of the problems with nudging in this recent piece.

‘…scientists overly rely on certain types of experiments. And they often don’t consider the benefits relative to the actual costs of using nudges, or work out whether nudges are in fact the actual reason for positive effects on behaviour.’

In America, a July 2022 study in Proceedings of the National Academy of Sciences concludes that once ‘publication bias’ towards positive results is removed ‘no evidence for the effectiveness of nudges remains’. As Osman writes, this doesn’t mean we should abandon the study of nudge-type interventions, but it does suggest there should be a good deal more caution when it comes to outsized claims for what nudging can or can’t do.

Trying to use subliminal cues instead of rational persuasion can also end up antagonising the very audience you are trying to influence. In 2021, for instance, the Australian government released a graphic health campaign to promote uptake of the Covid vaccine among young adults who were unlikely to suffer severe consequences from contracting the virus. The ad featured a young, unvaccinated woman on a ventilator and the caption ‘Covid-19 can affect anyone. Stay home. Get tested. Book your vaccination.’

The ad was retracted soon after its release due to a significant public backlash. Young people knew the ad was targeted at them and based on an unfair assumption that their refusal of the vaccination stemmed from disregard for elderly and immunocompromised people. At that stage, there were practical, legitimate reasons for slow vaccine uptake among under-40s: the Morrison government had only ordered AstraZeneca, which was primarily advised for the elderly, and had been releasing contradictory and rapidly changing vaccine guidelines.

We should take the ‘paternalism’ out of ‘libertarian’ and assume that adults make important decisions (like, their children’s education or their voting preference) based on rational choice. The information underlying their decisions may be limited but, addressing this shortcoming requires factual and open conversation, not cheap nudges.

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Frances An is a Mannkal Scholar and an intern at the Centre for Policy Studies.