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In a 1973 field experiment, preschoolers who already liked drawing were split into three groups: some were promised a reward for drawing, some got the same reward as a surprise afterwards, and some got none. Given free time later, the children who had expected the reward chose to draw less than the other two groups.

Mark Lepper, David Greene & Richard Nisbett, 1973

MindScience

The story behind the card

The study, by the psychologists Mark Lepper, David Greene and Richard Nisbett, took place at Bing Nursery School on the Stanford University campus. The prize was a “Good Player Award” card with a gold star and a red ribbon. One to two weeks later, the children who had been promised the award spent about 9 per cent of their free time drawing, against 17 to 18 per cent in the other groups. The authors were testing what they called the “overjustification” hypothesis: when people are led to see an activity as a way to earn a reward, their own interest in it can weaken. Later research found that it depends on the reward: expected, tangible prizes for something people already enjoy are the most likely to backfire, while praise usually does not.

Türkçe oku
1973'teki bir deneyde, resim yapmayı zaten seven anaokulu çocukları üç gruba ayrıldı: resim yaparlarsa ödül alacaklarını bilenler, aynı ödülü sonradan sürpriz olarak alanlar ve hiç ödül almayanlar. Daha sonra serbest zamanlarında, ödül bekleyen çocuklar öteki iki gruptakilerden daha az resim yapmayı seçti.

Deneyi psikologlar Mark Lepper, David Greene ve Richard Nisbett, Stanford Üniversitesi kampüsündeki Bing Nursery School adlı anaokulunda yaptı. Ödül, üzerinde altın bir yıldız ve kırmızı bir kurdele bulunan “İyi Oyuncu Ödülü” kartıydı. Bir iki hafta sonra, ödül sözü verilen çocuklar serbest zamanlarının yalnızca yüzde 9 kadarını resim yaparak geçirdi; öteki gruplarda bu oran yüzde 17-18'di. Araştırmacılar “aşırı gerekçelendirme” adını verdikleri varsayımı sınıyordu: İnsan bir işi ödül kazanmanın yolu olarak görmeye başlarsa, o işe duyduğu kendi ilgisi zayıflayabilir. Sonraki araştırmalar, sonucun ödülün türüne bağlı olduğunu gösterdi: Zaten sevilen bir iş için önceden vaat edilen somut ödüller ters tepebiliyor, övgü ise genellikle bu etkiyi yaratmıyor.

Sources and further reading

Background reading: Overjustification effect
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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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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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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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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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