As an aid to thinking about the difference between the two interpretations of ‘as judged by themselves’, I offer the following thought experiment. Consider Jane, one of the customers at Sunstein and Thaler’s cafeteria. Jane is currently in good health but seriously overweight. Professional dieticians would agree that her long-term health prospects would be better if she ate less high-fat, sugar-rich food (such as the cafeteria’s cream cake) and more fruit and vegetables (such as the cafeteria’s fresh fruit option). But, despite knowing what dieticians advise, she usually chooses the cake. Imagine that, in an attempt to uncover the reasoning that leads people like Jane to ignore dietary advice, we are designing a questionnaire which asks: ‘Which of the following statements best represents your reasons for choosing cake rather than fruit, contrary to the recommendations of health experts?’ The thought experiment is to produce statements that Jane might plausibly assent to, and that could be used to diagnose her mode of reasoning.
There should be one statement that picks up failures of self-control:
(a) I always go into the cafeteria having resolved not to choose cake, but when I see the cake at the front of the counter, I can’t resist the temptation.
Now for some others:
(b) I get a lot of pleasure from eating sweet and fatty foods, and the thought of living to a great age doesn’t appeal to me.
The first part of this statement describes a plausible taste, but the second part may pick up an empathy gap between age groups, compounded by lack of experience of the sources of happiness open to old people.
(c) When I am a few years older I will adopt a healthier diet, so my current eating habits are not a problem.
This statement may pick up procrastination (planning to change one’s behaviour in a future that is constantly being deferred) or an empathy gap (the respondent mistakenly imagines that her older self will be less susceptible to temptation, or will get less pleasure from food, than her present self does).
(d) The expert advice sets unrealistic standards. Most of the people I know eat at least as much sugar and fat as I do.
This statement picks up the heuristic of social proof, by which people match their behaviour to that of others, even if they cannot rationalise what those others are doing (Cialdini 1984). It may also pick up a self-serving bias in the selection of comparators.
(e) All my grandparents were thin but died relatively young. It’s quite likely that I will die young too, whatever I eat.
(f) All my grandparents were fat but lived to ripe old ages. It’s quite likely that I will have a long life too, whatever I eat.
These statements pick up the heuristic of availability, which induces a tendency to overweight personal experience relative to statistical evidence and to reports, however reliable, of other people’s experiences (Tversky and Kahneman 1973).
(g) Expert health advice is always changing; in a few years, experts may be recommending high-fat, high-sugar diets.
Expert health advice does change over time, but scepticism about the robustness of unwelcome recommendations may be a way of reducing cognitive dissonance by adjusting one’s beliefs to fit one’s preferences (Festinger 1957).
(h) Whatever I eat, I put on weight, so for me there is no point in trying to eat more healthily.
This statement may pick up self-deception about how much the respondent actually eats. It is known that people tend to under-report the calorie content of their diets (Murakami and Livingstone 2015).
The point of this thought experiment is that there are many ways in which a person can explain why she knowingly acts against well-grounded but unwelcome recommendations from experts. Failure of self-control is only one of these ways. My conjecture, based both on casual social experience and on general scientific knowledge about the prevalence of empathy gaps, procrastination, conformity, cognitive dissonance, self-deception and the tendency to overweight evidence from personal experience, is that lack of self-control would not be particularly common as a self-ascribed explanation; statements like (b), (c), (d), (e), (f), (g) and (h) would be more common.
Notice that each of the eight statements in my questionnaire represents a mode of reasoning, heuristic or bias that is known to be a common property of human psychology. However, (a) differs from the others in admitting to a failure on the part of the respondent herself: she has failed to choose as she intended (and, by implication, has failed to choose according to her own best judgement). All the other statements maintain that the respondent knows what she is doing and has chosen what, on balance, she believes is best for her. They maintain that the error is in the experts’ recommendation, applied without recognition of the respondent’s circumstances, not in the respondent’s failure to follow it. My guess is that most people prefer not to explain their own behaviour as the result of error.
It might be objected that by including an admission of error only in statement (a), I have introduced a bias into my argument. One might reasonably claim that none of the eight statements gives a valid reason for not following the expert recommendation. (Indeed, one might even say that, by treating an irresistible temptation as a constraint, (a) is unique in giving a valid reason.) But suppose we rephrase (a) so that, like the other seven statements, it does not involve an admission of error, but still picks up failures of self-control:
(a′) I have resolved not to eat cake very often, but if I’m feeling in the mood for cake, that’s what I choose. I don’t believe in being obsessive about my resolutions.
This statement allows the respondent to interpret breaking a resolution as showing spontaneity or flexibility rather than weakness of will. For that reason, respondents might be more likely to agree with (a′) than with (a). An external observer might judge (a′) to be a rationalisation of a failure of self-control. (Or he might not: it is entirely coherent to treat spontaneity as a desirable character trait.) But that is beside the point. My concern is with the distinction between the two interpretations of ‘as judged by themselves’. What is at issue is whether people—real human beings, not their imagined inner rational agents—want to be nudged. If Jane, in the cool emotional state of a questionnaire respondent, endorses her propensity to break her own resolutions, we are not entitled to claim that her cake-eating behaviour is contrary to her own judgements about what most matters to her.
My claim is that self-acknowledged self-control problems are a lot less common than many behavioural economists seem to think. Even if behavioural economists or policy makers feel confident that people’s lifestyle choices are based on some kind of error, they should not jump to the conclusion that the error is a self-acknowledged failure of self-control, or that (as Thaler puts it) it is what those people would themselves call an error.