Ikigai DailyAttention, memory and emotion
Discoveries about how we think, remember and make sense of experience.
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The card gives a free English version of a Ukrainian proverb, “Za durnoyu holovoyu rukam i noham nemaye spokoyu”: because of a foolish head, the hands and feet get no rest. The picture is an everyday one: forget your keys and your legs must carry you back for them. German says that what the head lacks, the legs must make up for. People also use the saying of groups, when a careless decision at the top is paid for by everyone below.
The phrase comes from the tenth Satire of the Roman poet Juvenal, written in the early 2nd century AD. The poem mocks people who pray for wealth, power, fame, beauty or a long life, since such wishes often bring ruin. If you must pray, Juvenal says, ask for “mens sana in corpore sano”, a sound mind in a sound body, and a brave heart that does not fear death. It later became a motto of sport, and in Turkey its Turkish form is often credited to Atatürk, the republic's founder.
Bruce Lee spoke this line as the martial arts teacher Li Tsung in the American television series Longstreet in 1971, at the end of a short speech about water taking the shape of whatever holds it. Later that year he repeated the idea in a television interview with the Canadian journalist Pierre Berton. The image echoes Taoist writing such as the Tao Te Ching, where water is soft yet wears away what is hard. Lee's own martial art, Jeet Kune Do, rests on the same idea: adapt to the opponent instead of holding to fixed forms.
Jung wrote this on 22 October 1916 to Fanny Bowditch, whom the Boston doctor James Jackson Putnam had sent to him for treatment. The letter opens with the same idea: as long as she looks at other people and projects her own psychology onto them, she can never be in harmony with herself. He adds that he is leaving for military service and will start work with her in December. Popular versions shorten the passage and turn “vision” into “visions”. The letter is in C. G. Jung: Letters, volume 1.
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.
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.
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.
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.
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.
The American psychologist Susan Nolen-Hoeksema made rumination a major research topic from 1991, describing it as passively and repeatedly focusing on distress and its possible causes and consequences. In a 1995 study with Sonja Lyubomirsky, people in a low mood who were asked to dwell on their feelings came up with less effective solutions to problems with other people than those who were first given something else to think about. Edward Watkins at the University of Exeter later showed that the style of thinking matters. Abstract “why” questions, such as “Why does this always happen to me?”, tend to keep people stuck, while concrete “how” questions, such as “How did this happen, and what can I do next?”, helped depressed patients solve problems better. Some therapies now teach people to notice when they are asking why and to switch to how.
In 1884 the American philosopher and psychologist William James turned the usual order around in an essay called “What Is an Emotion?”. We do not tremble because we are afraid, he argued; we feel afraid because we tremble. The physiologist Walter Cannon attacked the idea in 1927, and the debate ran for decades, but modern research keeps finding the body at the heart of emotion. In 2014 Lauri Nummenmaa and colleagues in Finland asked 701 people to colour in body outlines to show where they felt activity rise or fall with different emotions. Most emotions showed up in the chest, where breathing and heartbeat change; anger and happiness also lit up the arms, sadness appeared as weakened arms and legs, and disgust centred on the throat and stomach. The maps were similar for Finnish, Swedish and Taiwanese participants.
Psychologists call this store of events from one's own life autobiographical memory. The British psychologist Frederic Bartlett showed in his 1932 book Remembering that recall is reconstruction, not replay: when people retold an unfamiliar Native American folk tale, “The War of the Ghosts”, they gradually reshaped it to fit their own expectations. A striking modern example followed the Challenger space shuttle disaster in 1986. The morning after, Ulric Neisser and Nicole Harsch asked students to write down how they had heard the news, then asked again two and a half years later. Many accounts had changed a great deal, yet the students were confident in their new versions. Memory is also tied to identity. When older adults look back, they recall an unusually large share of events from between about 10 and 30, the years when a sense of self takes shape; this is called the reminiscence bump.
A night's sleep runs in cycles of about 90 minutes. Each cycle moves from light sleep into deep sleep and then into REM sleep, named after the rapid eye movements that come with it and the stage with the most vivid dreams. As early as 1924, the psychologists John Jenkins and Karl Dallenbach found that two volunteers remembered more of the nonsense syllables they had learned if they slept afterwards than if they stayed awake for the same time. In 2007, brain scans showed that after a night without sleep, the amygdala, an area involved in emotional reactions, responded far more strongly to upsetting pictures. In 2013, a study in mice found that the spaces between brain cells widen by about 60 per cent during sleep, helping fluid wash away waste. Regularly sleeping too little harms attention, learning and mood.
In 1953, Eugene Aserinsky and Nathaniel Kleitman at the University of Chicago noticed bursts of rapid eye movements (REM) during sleep and linked them to dreaming; people woken during REM sleep report a dream about 80 per cent of the time. Later studies found that people woken from other stages also report dreams, usually shorter and less story-like. Explanations differ. Sigmund Freud, in The Interpretation of Dreams (1899), saw dreams as disguised wishes. In 1977, Allan Hobson and Robert McCarley proposed that dreams are the brain's attempt to make a story out of random signals from the brainstem, the part of the brain that joins the spinal cord. Other researchers argue that dreams help us rehearse threats, sort memories or soften emotional experiences. Each theory explains some dreams, and none explains them all.
Nerve endings called nociceptors detect heat, pressure or chemicals that could harm tissue and send warning signals to the spinal cord and brain, but it is the brain that decides whether, and how much, it hurts. During the Second World War, the American anaesthetist Henry Beecher found that most of the badly wounded soldiers he treated did not ask for morphine, perhaps because surviving and leaving the battle outweighed the injury. In 1965, Ronald Melzack and Patrick Wall proposed the gate control theory: signals can be turned up or down in the spinal cord, which is partly why rubbing a knock helps. Phantom limb pain, felt in an arm or leg that has been amputated, shows that pain can exist where there is no tissue. In 2020 the International Association for the Study of Pain revised its definition, noting that pain and nociceptor activity are not the same thing.
Georges Duhamel (1884–1966) was a French doctor who spent four years as an army surgeon in the First World War and won the Prix Goncourt, France's best-known literary prize, in 1918. He wrote La Possession du monde (The Heart's Domain) during the war. Shortly before this line he recalls that the war let him see his child only seven times, each time barely recognising him; now he keeps seven images of him. Our feelings, he adds, take their true colour only later, like prints in a photographer's gold bath.
From La Possession du monde (The Heart's Domain, 1919), which the French writer Georges Duhamel wrote while serving as an army surgeon in the First World War. In a chapter on sharing one's discoveries with others, he recalls a friend who said almost every day that he had had a beautiful thought that morning and lost it. So keep a small notebook, Duhamel advises: the soul is a rushing river carrying mud, grass, flowers and gold, and the nuggets must be set aside before the current takes them.
The proposal, 'Information Management: A Proposal', described a real problem. Most scientists stayed at CERN for about two years and then left, so knowledge was constantly being lost, and even written records were hard to find among the lab's many incompatible computers. His answer was hypertext: documents containing links that lead straight to other documents, spread across a network. He had tried a small version of the idea for himself in 1980, a program called ENQUIRE. The proposal drew little interest at first. He sent it round again in May 1990 and, with the Belgian engineer Robert Cailliau, turned it into a formal project plan that November. Sendall let him build the system on a newly bought NeXT computer, and after considering names such as 'Information Mesh', Berners-Lee settled on World Wide Web.
Memory consolidation is the slow process that turns a fresh, fragile memory into a lasting one, and much of it happens during sleep. In 1997 the German researchers Werner Plihal and Jan Born showed that different parts of the night help different kinds of memory. Twenty healthy men learned lists of word pairs and practised mirror tracing, drawing a shape while watching only its reflection. Recall of the word pairs improved most over the first half of the night, when deep, slow-wave sleep dominates, while the drawing skill improved most over the second half, when REM sleep, the stage of vivid dreams, lasts longer. Researchers think that during sleep the brain replays the day's experiences and moves new memories from temporary storage in the hippocampus, deep in the brain, into longer-lasting networks in its outer layer, the cortex.
The CDC (Centers for Disease Control and Prevention) is the United States' national public health agency, founded in Atlanta in 1946. Its advice on exercise follows the Physical Activity Guidelines for Americans, whose second edition, published in 2018, drew on a review of the previous decade's research. Earlier advice had focused on preventing disease over the years; the new edition also listed benefits people can feel at once. Besides easing anxiety and lowering blood pressure, a single session helps the body respond to insulin, the hormone that moves sugar from the blood into cells. Most of these effects grow with regular activity, while others, such as fitness, strength and a lasting fall in blood pressure, take weeks or months. The guidelines recommend at least 150 minutes of moderate activity a week.
The World Health Organization counts any movement that uses energy as physical activity: walking, cycling, sport, active play, housework and physical work. Its 2020 guidelines advise adults to do 150 to 300 minutes of moderate activity a week, such as brisk walking, or 75 to 150 minutes of vigorous activity, such as running, plus muscle-strengthening exercise on at least two days. In 2022 about 31% of adults worldwide, some 1.8 billion people, fell short of that. Weight is a poor guide to these benefits. The US Physical Activity Guidelines state that they are generally independent of body weight, and a 2014 analysis of ten studies found that fit people who were overweight or obese had death rates similar to fit people of normal weight, while unfit people had about twice the risk, whatever their weight.
For much of the 20th century scientists believed the adult brain was more or less fixed. Brain scans changed that view. In 2004 researchers in Germany taught adults to juggle three balls over three months; scans showed extra grey matter, the tissue packed with nerve cells, in areas that track moving objects, and it shrank back once they stopped practising. A follow-up in 2008 found the same kind of change in volunteers around 60 years old, although they learned less well than 20-year-olds. The best-known example comes from London, where Katherine Woollett and Eleanor Maguire followed trainee taxi drivers for four years as they memorised the city's 25,000 streets. Those who passed the exam gained grey matter at the back of the hippocampus, a region involved in finding our way; those who failed, and people who never trained, showed no such change.
The Canadian psychologist Donald Hebb proposed the idea in his 1949 book The Organization of Behavior: when one nerve cell repeatedly helps to fire another, the link between them becomes more efficient. It is often summed up as “cells that fire together wire together”. In 1973 Timothy Bliss and Terje Lømo found such strengthening in the brains of rabbits in Oslo: after bursts of electrical stimulation, connections in the hippocampus, a region vital for memory, stayed stronger for hours. The effect is called long-term potentiation. Practice can reshape the brain within days. In 1995 Alvaro Pascual-Leone and colleagues at the US National Institutes of Health had volunteers practise a one-handed, five-finger piano exercise for two hours a day. After five days, the area of the motor cortex that controls the finger muscles had grown larger.
The study was led by Jessica Payne of the University of Notre Dame, with colleagues including Robert Stickgold of Harvard Medical School. Volunteers learned pairs of words at 9 am or 9 pm. Twelve hours later those who had slept remembered more, mainly because a day awake had worn away memory for pairs of unrelated words, which are harder to link in the mind. After 24 hours everyone had had one night's sleep and one day awake, only in a different order, and those who slept soon after learning still remembered more. Memory also faded more slowly across a day awake when a night's sleep had come first, which suggests that sleep steadies new memories against the interference of waking life. It is one reason sleep researchers advise against giving up sleep to cram for an exam.
