When dozens of apparently healthy young men who had emigrated from Laos started dying in their sleep in the late 1970s, US medical authorities couldn’t fathom what was going on. They termed the phenomenon “sudden unexpected nocturnal death syndrome”, but that was just a label for their bafflement. Today, we think we know the cause: the men experienced sleep paralysis, which is common and harmless in itself; but they understood it as a visitation from the dab tsog, a malevolent spirit who sits on victims’ chests at night. Living far from the shamans and family members who might have helped them ward off the evil, the men panicked, probably exacerbating a form of heart arrhythmia more prevalent in people from south-east Asia, and triggering cardiac arrest.
The science writer David Robson’s mission in The Expectation Effect is to convince us we shouldn’t look on those men with condescending pity: our own expectations and beliefs, however irrational, influence our health, happiness and our survival no less decisively. Take, for example, ageing: if you think it’s a matter of inevitable cognitive decline and becoming useless to society, you’re more likely to experience hearing loss, frailty, even Alzheimer’s. Such attitudes predict higher levels of stress and inflammation, which in turn contribute to a range of disorders. (By contrast, in places such as Sardinia, where centenarians are numerous and thriving, their role in intergenerational households is thought to be a factor: it encourages them to expect to stay active.) If you convince yourself that you’re prone to insomnia, you’ll suffer the symptoms of insomnia – even if the truth is that you sleep fairly well. And it’s common for participants in medical trials to experience not only the placebo effect but the “nocebo effect” – drug side-effects such as nausea, dizziness or rashes, even though they’re only taking sugar pills.
To an extent, the “expectation effect” is the stuff of self-help cliche: “Whether you think you can or think you can’t, you’re right,” Henry Ford is supposed to have said, rather irritatingly. But one of Robson’s many strengths as a chronicler of science is to take what might seem familiar and show – to his own evident excitement, as well – just how much deeper the rabbit hole goes. You knew about the placebo effect. But did you know it often works, a little mind-bendingly, even when the patient knows they’re taking a placebo? (This is promising, in terms of medical ethics, because it suggests that people need not be deceived in order to benefit.) And if you knew that, did you know there’s evidence that the placebo effect is growing more powerful over time, as more people learn of the placebo effect, and thus expect to experience it? That’s right: the placebo effect has a placebo effect. Expect your expectations to change your life, and they will.
While the book abounds in compelling anecdotes – the cyclist who thought he was injecting performance-enhancing drugs, and performed better accordingly; the Portuguese TV show that caused an outbreak of breathing difficulties in its viewers – Robson’s central point is that the expectation effect isn’t an amusing psychological quirk, but a fundamental aspect of our interactions with reality.
Our brains are “prediction machines”, steering us through life by generating expectations, and only revising them when unavoidable. Those expectations then play a vital role in shaping what we experience. This explains why far more people, especially children, see a rabbit in the famous “duck-rabbit” optical illusion around Easter than at other times of year. But it also helps explain why pupils from low-income backgrounds tend to live down to their teachers’ academic expectations – and why some of those teachers tend to react with discomfort, not pride, should they defy their assumptions instead. “Like a dramatist carefully crafting a narrative arc,” Robson writes, “we don’t like the objects of our expectations to go off script.”
Robson is aware of the objection that this might all sound like a paean to positive thinking. He rejects that claim: the expectation effect concerns specific outcomes, not a general effort to feel good. Moreover, the cult of positivity reinforces the idea that merely experiencing negative emotions constitutes a crisis, or a personal failing, leading only to more negative emotions: “By demonising unpleasant but inevitable feelings, we have been creating a potent nocebo out of modern life.”
In any case, wisely harnessing the power of expectation isn’t a matter of eliminating bad things so much as reframing them – for example, by understanding the feelings of exertion during exercise as evidence that you’re making yourself fitter. (Likewise, I think “writer’s block” is often best thought of simply as what it feels like to push yourself creatively.) That way, apart from anything else, you’re far less likely to quit when the going gets tough. Startling research even shows that when people are encouraged to think of the physical movements in which they already engage for their jobs as exercise, they reap greater health benefits.
The result of marinating for a while in this outlook is surprisingly transformative. We’re accustomed to thinking of the external world as an implacable thing that either lives up to, or more commonly frustrates, our expectations. That’s why I’ve always been fond of “defensive pessimism”: keep your expectations low, and you can only ever be pleasantly surprised. But this approach defines our expectations as wholly impotent: vain hopes that reality might or might not deign to fulfil. The Expectation Effect shows that, on the contrary, our expectations participate actively in that reality.
Clearly, believing that you could be a champion salsa dancer in your 80s – to pick one of Robson’s examples – doesn’t guarantee that you will be. But it might prove easily as important as the genes you were born with. We defensive pessimists could do with remembering that sometimes things do actually turn out really well – especially if you expect them to.
• The Expectation Effect: How Your Mindset Can Transform Your Life by David Robson is published by Canongate (£18.99). To support the Guardian and the Observer buy a copy at guardianbookshop.com. Delivery charges may apply.