Let’s say that you see that people who rate themselves highly on the scale are more likely to have quit than people who don’t. For example, people who gave themselves an eight or higher were twice as likely to be smoke-free after six months than people who gave themselves a four or below.

What’s your conclusion here? If you are Professor Ian Robertson, a clinical psychologist and author of How Confidence Works: The new science of self-belief, why some people learn it and others don’t, then the conclusion is obvious. Confidence helps you quit. If you believe — if you truly believe — that you have the willpower to quit, then you can do it! You have the “can happen” and the “can do” mentality, and that will drive you over the finish line!

If you’re anybody else, of course, you might point out that all this shows is that people can judge their own abilities quite well. I’m not confident in my ability to beat Magnus Carlsen at chess, and I expect Carlsen would be very confident in his ability to beat me. If we then played and I lost, I don’t think that would be because I was inadequately confident. In the same vein, if I know I’ve got a really bad 40-a-day habit and shitty willpower, then I’ll probably judge that I won’t be able to quit, and I may well be right. But it’s not that I’ll fail because I’m not confident; I’m not confident because I rightly think I’ll fail.

I’ve made up the smoking example, but Robertson uses several similar ones. “Studies have shown,” he says, right at the start of the book, “that you will live longer after heart failure if your partner feels confident about your condition.” If you find the study (not studies) he’s referring to,[1. Which is a pain in the arse to do, by the way, because he doesn’t use SODDING FOOTNOTES. Use footnotes! It’s fine! Readers don’t get derailed by little superscript numbers in the text!] you see that it does indeed find that heart disease patients are more likely to live longer if their spouses have high confidence that they will survive.

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But… if I were to develop heart disease tomorrow, and you were to ask my wife whether she thinks I’ll survive the next six months, her answer wouldn’t simply be a product of whether she’s a confident, happy-go-lucky sort of person. It would also be based on her assessment of my health, my ability to stick to exercise and diet regimes, whether or not I tend to stick my fingers in electrical sockets for fun. She might say: “My husband is relatively young, and reasonably fit, so that’s positive, but on the other side of the ledger he’s a lazy git and eats too many burgers, so overall I’ll give it 60%.”

(To be fair, the study tries to look out for this by controlling for disease severity. But I would imagine that spouses are better judges of a person’s overall health than a four-category NYHA classification.)

For Robertson, though, confidence is everything. It’s the most important thing in the world. And everywhere he looks, science backs this up. It’s astonishing. A Duke University study looking at twins found that if one member of a pair of twins assesses their family’s social status as lower, that twin will likely do worse in life: worse jobs, more crime, etc. For Robertson, “something happened during adolescence that made some of the twins feel that they had lower social status than their sibling. Once they felt that, their behaviour, mental health, education, job and optimism suffered accordingly.”

The possibility that the causal arrow points the other way – that when a twin’s life starts to go down the toilet, they start to assess their (and their family’s) status more negatively – simply does not occur to him.

There are dozens of things like this. People who are pessimistic die young, people who are less confident in their memory are more likely to get dementia, people who walk more slowly are less confident in their health and will therefore die young. The possibility that people are accurately judging their own health status is occasionally raised but then dismissed. (Sometimes the studies controlled for other possibilities, but did they control for enough?)

Which is a shame. There is a fascinating book to be written by someone with a bit more self-reflection — someone a bit less confident, perhaps, in their thesis. Robertson divides confidence into two constituent parts: a “can happen” attitude and a “can do” attitude. If we’re trying to lose weight, say, someone might tell us to eat a healthier diet and take more exercise.

If we believe that salad and jogging will have the desired effect – that we would, if we ate better and ran more, lose weight — then we have a “can happen” attitude. And if we believe that we are personally capable of eating better and running more, then we have a “can do” attitude. Confidence, he says, is a “bridge to the future”: it is our mind’s ability to visualise our ability to get from here, where we are, to there, where we want to be.

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Robertson illustrates the idea with stories of CEOs and sportspeople and so on who have, as he says, this can happen/can do attitude, and how they therefore changed the world. 

But there’s another way of thinking about confidence: it’s just your brain predicting, given the information it has, how likely it is to succeed. You could imagine an AI that was built to perform some task, say image recognition. You train it on eleventy billion pictures of dogs and cats, and then you make it look at some other images of dogs and cats and say which ones are which. You feed it a thousand pictures and it gets 980 of them right.

Then you ask it (it’s also a natural-language AI) how confident it is that it will get the next one right. It says “98%.” Then it gets the next one wrong.

Why did it get the next one wrong? Is it because it wasn’t confident enough? No: it has correctly assessed that it will get it right 49 times out of 50. If the AI had said it was 99% confident, it would have been overconfident. The AI has learnt, from its experience of its own capabilities and the difficulty of the dog-cat-recognition task, that it gets it right 98% of the time.

And if the AI has to make some decisions based on its ability to tell a picture of a cat from a picture of a dog, it can only make those decisions rationally if it assesses its own skill accurately. If you offered it a bet at £1 to £25, it would be rational to take that bet; if you offered it a bet at £1 to £100, then it would not. Similarly, a human being asked “Can you quit smoking?” is making an assessment of his or her abilities, and will take action according to how likely he or she thinks they are to succeed.

Of course, you might say, AIs aren’t human. We do misjudge our own abilities, either overestimating or underestimating them, and it does feel from the inside as though confidence drives success as well as success driving confidence. And there might be some scientific evidence supporting that. This would have been the interesting book Robertson could have written: the book teasing out the difference between confidence-as-assessment-of-skill and confidence-as-motivation.

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Unfortunately, Robertson’s actual book is, again, so confident in the importance of confidence that he overlooks the shakiness of the science he cites. I’ve written and read a lot about the “replication crisis” over the last few years, and you get a bit of a sense for the sort of psychology studies which will turn out to be garbage. And my alarm bells were ringing constantly as I read this book.

For one thing, it repeatedly mentions psychological findings, such as stereotype threat, social priming, impostor syndrome, the “hot hand” effect, the Dunning-Kruger effect, and growth mindset, which have variously either been debunked or at least need some sort of acknowledgment that they’re controversial. 

More generally, it regularly quotes studies which seemed odd — so I went and looked about two dozen of them up. Studies into things like whether wearing a lab coat makes you better at concentrating, or whether being told that you’re smarter makes your brain look different in an fMRI scanner. Time after time, it was an unpreregistered study looking at 27 undergraduates which barely reached statistical significance. I am, I’m afraid, extremely not confident that most of these studies would replicate (and several of them definitely have not).

I have three hypotheses for why Robertson, who as a neuroscientist and psychologist is presumably aware of the replication crisis, might overlook the shakiness of the studies supporting his thesis. One is charitable: the others less so.

The charitable explanation is that Robertson is a clinical psychologist. If this book were a book of robust science, it would be full of caveats and on-the-one-hand-on-the-others. But perhaps it’s not. Perhaps it’s a self-help book: “Get confident, stupid!” Robertson wants to get his readers to maximise their confidence, so he pushes its importance and overstates the effectiveness of various tricks to improve it. It is full of pretty common-sense advice (tell yourself you’re excited rather than anxious, etc); maybe he feels that’ll do more good if it’s backed up with neurobollocks about how it’s all to do with dopamine receptors in the ventral striatum or whatever.

The first less charitable explanation is that Robertson, like many other moderately famous psychologists, has his eye on the lucrative after-dinner speaking market, and the way to get on that is to say that This One Weird Trick is all you need to totally change your life, whether it’s growth mindset or “grit” or power posing or whatever. In this model, Robertson has decided that “confidence” is the new “positive psychology”, and he can get £10,000 a go for 45 minutes talking to postprandial advertising executives in a conference hall in the Runnymede Marriott.

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The second less charitable explanation is … well. Robertson tells the story of Ally McLeod, who took Scotland to the World Cup in 1978, promising not only to win it but to retain it the next time around. Scotland were instead knocked out in the group stages . “Ally MacLeod was what is colloquially known as a bullshitter,” he says. My own understanding of “bullshit”, in the Harry Frankfurt sense, is speech in which the speaker doesn’t care whether he is telling the truth or not; but for Robertson, it’s essentially problematic overconfidence, misjudging your own expertise and abilities. It is possible that one or both of those two definitions might apply to this book.

But this book is what it is. One of Robertson’s key anecdotes is of Padraig Harrington, the golfer, having a moment of doubt while comfortably in the lead in the 2007 British Open, and then repeatedly whiffing his ball into a lake, almost throwing his lead away, and then getting his confidence back and going on to win. There’s a fascinating story there to be told — was the confidence (and its disappearance) a product of how well he was doing or wasn’t, or the other way around? Did they feed back into each other in a complex, self-reinforcing loop? And was that initial moment of doubt even real, or was it added into his mind with hindsight? (It’s not as if memory is infallible.) I would love to have read someone treating that complicated story with the subtlety it deserves.

But for Robertson, the story is simple. Harrington was confident, so he was winning; then he stopped being confident, so he stopped winning; then he got confident again, so he won. The end. Get confident, stupid.