Why there is no scientific consensus on the “nudge” 

You may have nev­er real­ised it, but chances are you’ve already been influ­enced by a “nudge”. Accord­ing to the two the­or­ists behind the term, Richard Thaler and Cass Sun­stein, nudges are sug­ges­tions that aim to influ­ence and change people’s beha­viour in a pre­dict­able way. This is done without pro­hib­it­ing any option, without any real fin­an­cial incent­ive and without provid­ing addi­tion­al information. 

A well-known example of a nudge is the little fly inser­ted in the urin­als of the toi­lets at Ams­ter­dam air­port, which is said to have greatly reduced the work­load of the clean­ers, as men using them “aim bet­ter” thanks to this simple addi­tion. With this example, we can see that it is human beings who are the tar­get of nudges.  People steeped in cog­nit­ive biases (accord­ing to the Kahne­mani­an paradigm in beha­vi­our­al eco­nom­ics) and sens­it­ive to social influ­ences, as opposed to oth­er paradigms such as the eco­lo­gic­al ration­al­ity developed by Gerd Giger­en­zer. Indeed, accord­ing to both the­or­ists, nudges are aimed at “mere mor­tals” and not at the homo eco­nomicusof clas­sic­al eco­nom­ic theory. 

How­ever, the term nudge is rather gen­er­ic, and it is dif­fi­cult to know what we are really talk­ing about when using it. And there are still grey areas in the way it is char­ac­ter­ised – not all authors agree on the defin­i­tion. “Depend­ing on the inten­tions of the nudger or the con­form­ity with the right decision, we can find dif­fer­ent ter­min­o­lo­gies such as dark nudge or sludge,” explains Daniel Pri­olo. “All these notions were inven­ted after the demon­stra­tion of the effects of influ­ence in social psy­cho­logy and our cog­nit­ive biases in beha­vi­our­al economics.” 

There are still grey areas with­in its char­ac­ter­isa­tion, and not all authors agree on the same definition.

Some even dis­pute the cent­ral idea that the nudge should not be pro­hib­it­ive. Emma Tief­fen­bach, PhD in eth­ics and a spe­cial­ist in the eth­ics of giv­ing, who works mainly on char­it­able nudges at the Uni­ver­sity of Geneva, sug­gests that in some cases a ban can be under­stood as a nudge. “Loc­al bans on smoking, for example at an air­port, can be seen as nudges,” she says. “If someone really wants to smoke, they can walk a hun­dred metres or so and go out­side to do so. The oppor­tun­ity is not taken away, it just requires an extra effort on their part.”

Some clas­sic­al examples of nudges include the default option (your phone set­tings, for example), forced inter­ven­tion to com­plete a pro­cess (when the bank’s ATM asks you to with­draw your card to get your notes) or eye-level place­ment (when the “health­i­est” food is placed at eye level). Nudge advoc­ates say that all these tech­niques are sup­posed to make your life easi­er and guide you towards bet­ter choices – assum­ing they are effective. 

Mech­an­isms and prac­tises of nudges are mixed. “To say that nudges are or are not effect­ive is a bit like say­ing that med­ic­a­tion works,” sug­gests Daniel Pri­olo. Indeed, the par­al­lel with medi­cine is rel­ev­ant because the effect­ive­ness of a drug always depends on the effect size of the inter­ven­tion, spe­cif­ic judge­ment cri­ter­ia, a bene­fit-risk bal­ance, and a con­text. The same applies to nudges. 

Nev­er­the­less, there is cur­rently no con­sensus on the effect­ive­ness of nudges. A recent meta-ana­lys­is pub­lished in the Pro­ceed­ing Nation­al Academy of Sci­ence¹ sug­ges­ted their over­all effect­ive­ness… before being cri­ti­cised by oth­er authors who claimed that this effect­ive­ness was no longer rel­ev­ant when pub­lic­a­tion bias was con­sidered to adjust the res­ults².

In the sci­entif­ic com­munity there is as much enthu­si­asm regard­ing nudges as there is cri­ti­cism. Giv­en their norm­at­ive object­ives, they are also widely dis­cussed in the field of eth­ics and polit­ic­al sci­ence: what are the accept­able lim­its of their use? How can we tell the dif­fer­ence between a mor­al and an immor­al nudge? Let’s ima­gine that a nudge is imple­men­ted to make you choose a fruit salad rather than a chocol­ate cake in the cafet­er­ia. Yet today you really wanted cake. You might think there’s a prob­lem here, how­ever Emma Tief­fen­bach does not. “Nudges are not eth­ic­ally prob­lem­at­ic if they make us act in accord­ance with our second-order pref­er­ences,” she says. 

Second-order pref­er­ences are all those things that we would prefer to do (the ‘fore­see­ing self’ accord­ing to Thaler and Sun­stein), but fail to do because of our first-order pref­er­ences that make us act in the oppos­ite way (the ‘act­ing self’). In the­ory this makes sense, although in real­ity it is very dif­fi­cult to assess this con­form­ity. “All we see in real­ity are people who appear to be influ­enced by nudges, but it is very dif­fi­cult to know wheth­er they are act­ing in accord­ance with what either their second-order pref­er­ences or their good judg­ment would lead them to do,” warns Emma Tieffenbach.

On the oth­er hand, nudges are prob­lem­at­ic if they influ­ence indi­vidu­als without respect­ing their autonomy. “Nudges do not exploit our delib­er­at­ive capa­cit­ies but our cog­nit­ive or affect­ive biases, or our exag­ger­ated aver­sion to cer­tain emo­tions such as shame or guilt. And this can be eth­ic­ally prob­lem­at­ic,” says Emma Tief­fen­bach. This leads to debates among eth­i­cists: some con­sider that the viol­a­tion of autonomy is suf­fi­cient to pro­hib­it the use of nudges, oth­ers sug­gest that the bene­fi­cial con­sequences of nudges from a glob­al point of view jus­ti­fy their use. 

In the sci­entif­ic com­munity there is as much enthu­si­asm regard­ing nudges as there is criticism.

Some nudges may exploit people’s excess­ive aver­sion to cer­tain emo­tions, such as shame, embar­rass­ment, or guilt. For example, char­ity nudges most often exploit the desire to avoid the guilt asso­ci­ated with the option of keep­ing money to one­self. “In this case, the nudge acts on indi­vidu­als by asso­ci­at­ing cer­tain options, for example, hav­ing a cigar­ette in the smoking area of an air­port, often a glass room, under the poten­tially con­des­cend­ing gaze of pass­ers-by, with an exper­i­ence of shame that could deter even the most addicted smoker. What is prob­lem­at­ic is that the men­tal cost asso­ci­ated with the option to smoke may be no dif­fer­ent in intens­ity and dis­com­fort than that of a fine. In this case, it is ques­tion­able wheth­er the free­dom to smoke is really pre­served,” says Emma Tieffenbach.

From a more polit­ic­al point of view, nudges are sub­ject to three main cri­ti­cisms. They are sus­pec­ted of favour­ing the status quo; of delay­ing the imple­ment­a­tion of truly effect­ive meas­ures at a sys­tem­ic level; and of allow­ing excess­ive blame to be placed on the indi­vidu­al. A recent review pub­lished in Beha­vi­or­al and Brain Sci­ences lists these cri­ti­cisms and gives sev­er­al con­crete examples³. 

To illus­trate the prob­lem of the status quo, ima­gine a slum­lord in a devel­op­ing coun­try. He might claim that people are unhealthy because they do not fol­low hygiene rules or because their diet is unbal­anced. The nudge policy could then be used to increase the use of soap or to choose bet­ter foods. How­ever, the real reas­on for the poor health of the pop­u­la­tion seems to be the gen­er­al liv­ing con­di­tions of these people, and it is a real social policy towards hous­ing that will solve the afore­men­tioned problems.

With regard to the oth­er two issues, the example of green nudges, such as the roll-out of Linky smart meters to all house­holds in the coun­try in France, can be taken. Although the aim of green nudges here is to help cit­izens become more aware of their energy con­sump­tion, some con­sider that they place much of the respons­ib­il­ity for energy prob­lems on house­holds without ques­tion­ing the over­all energy policy. Nev­er­the­less, the gov­ern­ment seems to be aware of these prob­lems⁴, and cri­ti­cises nudges for not allow­ing rad­ic­al changes in both beha­viour and systems.

How­ever, this does not pre­vent it from mak­ing fre­quent use of nudges. “The gov­ern­ment reg­u­larly calls on the Dir­ec­tion Inter­min­istéri­elle de la Trans­form­a­tion Pub­lique (DITP) and the beha­vi­our­al sci­ences depart­ment with­in it to pro­duce visu­al com­mu­nic­a­tions and advert­ising spots. This was not­ably the case dur­ing the Cov­id-19 pan­dem­ic,” attests journ­al­ist Audrey Chabal, who pub­lished the invest­ig­a­tion Sour­iez, vous êtes nudgé (Smile, you have been nudged) on the use of nudges dur­ing the pan­dem­ic. “But it was not only the DITP that was respons­ible for this. For example, the BVA research com­pany hired by the gov­ern­ment sub­mit­ted the idea of using the ter­min­o­logy of “1^st, 2^nd and 3^rd line jobs” to the gov­ern­ment in order to get people to accept the idea that some people could go out to work while oth­ers would remain work­ing from home.”

To sum up, nudges are very diverse tools with mixed effect­ive­ness and some­times prob­lem­at­ic con­sequences. While there is cer­tainly a range of pos­sib­il­it­ies with­in which they can be use­ful, it is import­ant to always take a step back and not for­get that oth­er levers exist to change the beha­viour of a population. 

Julien Hernandez