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The curse of knowledge is the difficulty of imagining what it is like not to know something you know. Economists named it in 1989, after better-informed people in an experiment kept letting their own knowledge leak into predictions of what less-informed people would do, even when paid to be accurate.

Colin Camerer, George Loewenstein & Martin Weber, 1989 study

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The story behind the card

The study, by Colin Camerer, George Loewenstein and Martin Weber, gave some participants real information about companies' earnings and asked them to predict the forecasts of people who lacked it. Their guesses kept drifting towards what they themselves knew. A famous later demonstration came in 1990, when the Stanford graduate student Elizabeth Newton asked people to tap out well-known songs such as 'Happy Birthday' on a table. The tappers expected listeners to name about half the songs; the listeners named 3 out of 120. The tappers could hear the melody in their heads, and the listeners could not. The same bias explains why experts skip steps that feel too obvious to mention when they explain something to a beginner.

Türkçe oku
Bilgi laneti, bildiğimiz bir şeyi bilmeyen birinin yerine kendimizi koymakta zorlanmamızdır. İktisatçılar bu adı 1989'daki bir deneyden sonra koydu: daha çok bilgisi olan katılımcılar, az bilenlerin ne yapacağını tahmin ederken kendi bilgilerini bir kenara bırakamıyordu, üstelik doğru tahmin için para almalarına rağmen.

Colin Camerer, George Loewenstein ve Martin Weber'in çalışmasında bazı katılımcılara şirketlerin kazançlarıyla ilgili gerçek bilgiler verildi ve bu bilgiye sahip olmayanların nasıl tahmin yürüteceğini kestirmeleri istendi. Tahminleri durmadan kendi bildiklerine doğru kaydı. Daha sonraki ünlü bir gösteri 1990'da geldi: Stanford'da doktora öğrencisi olan Elizabeth Newton, katılımcılardan “Mutlu Yıllar” gibi bilinen şarkıların ritmini masaya vurmalarını istedi. Vuranlar, dinleyicilerin şarkıların yarısını bileceğini sanıyordu; dinleyiciler 120 şarkıdan yalnızca 3'ünü bildi. Çünkü vuranlar ezgiyi kafalarında duyuyordu, dinleyiciler duymuyordu. Uzmanların bir şeyi yeni başlayan birine anlatırken kendilerine fazla bariz gelen adımları atlaması da aynı yanılgıdan kaynaklanır.

Sources and further reading

Background reading: Curse of knowledge
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Deliberately smiling can make people feel slightly happier. In 2022 a study of nearly 4,000 people in 19 countries found that posing a smile, or copying a smiling face, raised reported happiness a little; a subtler method, holding a pen between the teeth, gave less clear results.

The idea that the face can feed back into feelings, called the facial feedback hypothesis, goes back to Charles Darwin and William James. In a famous 1988 experiment, Fritz Strack and colleagues had people hold a pen in their teeth, which forces a smile, or between their lips, which prevents one, and those in the first group rated cartoons as funnier. In 2016, seventeen laboratories repeated that experiment exactly and found no effect. A 2019 review of 138 studies concluded that the effect is real but small and varies from study to study. The 2022 Many Smiles Collaboration, led by Nicholas Coles and designed jointly by supporters and sceptics of the idea, found that deliberate smiling could both strengthen and start feelings of happiness, while the pen method remained inconclusive.

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Your gut and brain communicate through nerves, hormones, immune signals and microbes, which is why stress and digestion can affect each other.

Scientists call this link the gut–brain axis. The gut has its own network of about 500 million nerve cells, the enteric nervous system, sometimes called the “second brain”, which can run digestion largely by itself. It is connected to the brain mainly through the vagus nerve, a long nerve running from the brainstem down to the abdomen, and most of its fibres carry messages upwards, from the gut to the brain. More than 90 per cent of the body's serotonin, a chemical messenger, is found in the gut. Gut bacteria play a part too: in a 2004 Japanese study, mice raised entirely free of germs overreacted to stress. Stress can speed up or slow down the gut, one reason it often worsens irritable bowel syndrome, a common gut disorder. Most research on the microbes' role has been in animals, and human evidence is still limited.

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A placebo is a dummy treatment, such as a sugar pill. In pain studies, placebos can reduce the pain people report and also dampen activity in the brain areas that process pain, even though they contain no active drug.

The word placebo is Latin for “I shall please”. One of the first clues that the effect is physical came in 1978, when Jon Levine and colleagues studied patients recovering from wisdom tooth removal. They gave them a placebo and naloxone, a drug that blocks the effect of endorphins, the body's own painkilling chemicals. In patients who had responded to the placebo, naloxone increased the pain, which suggested that the placebo relief came from endorphins. In 2004 Tor Wager and colleagues used brain scans to show that a placebo painkiller reduced activity in pain-processing regions during a painful stimulus. Expectation works the other way too: in the nocebo effect, from the Latin for “I shall harm”, expecting harm makes symptoms worse. None of this means the pain was imaginary, or that placebos can replace effective treatment.

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Memory does not work like a recording. Each time we recall an event, the brain rebuilds it from stored fragments, filling gaps with what we know and what we have heard since, so a memory can change without our noticing.

Psychologists call this reconstructive memory. In his 1932 book Remembering, the British psychologist Frederic Bartlett described asking people to retell “The War of the Ghosts”, a Native American folk tale unfamiliar to them; each retelling drifted towards what felt familiar in their own culture. In 1974 Elizabeth Loftus and John Palmer showed people films of car accidents and asked how fast the cars were going when they “hit” or “smashed” into each other. Those asked with “smashed” gave higher speeds, and a week later were more likely to remember broken glass that was never there. This is known as the misinformation effect. It matters in court: according to the Innocence Project, mistaken eyewitness identification played a part in most US convictions later overturned by DNA evidence.

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Predictive processing, an influential theory in neuroscience, says the brain does not simply wait for information from the senses. It keeps guessing what is out there and uses the incoming signals mainly to check and correct those guesses.

The idea goes back to the German physicist Hermann von Helmholtz, who argued in the 1860s that seeing involves “unconscious inference”: the brain fills in what the eyes cannot fully tell it. In 1999 the researchers Rajesh Rao and Dana Ballard turned this into a computer model of vision. Higher brain areas send predictions down, and lower areas send back only the difference between prediction and input, called the prediction error. The philosopher Andy Clark and the neuroscientist Karl Friston later helped develop it into a broad theory of the mind. A well-known illustration is the hollow-mask illusion: the inside of a mask still looks like a face bulging outwards, because the brain's expectation of a normal face outweighs the evidence. The theory is widely used but still debated, and critics ask how some of its claims could be tested.

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