Mind: quotes, facts and reflections - Page 2

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DriveHealth

According to US health guidance promoted by the CDC, adults who sit less and do any amount of moderate or vigorous activity gain some health benefits. Since 2018 even a few minutes count, such as climbing a few flights of stairs; earlier advice counted only sessions of 10 minutes or more.

The Physical Activity Guidelines for Americans are issued by the US Department of Health and Human Services, and the CDC, the country's national public health agency, turns them into everyday advice. The first edition, in 2008, said activity had to last at least 10 minutes at a time to count, because there was too little evidence about shorter bouts. For the 2018 edition an advisory committee reviewed the newer research and concluded that activity of any length adds to the benefits. It also found that, for the risk of dying early, the biggest gain comes when an inactive person starts doing just 60 minutes a week: in the guidelines' words, some physical activity is better than none. The full target for adults remains 150 to 300 minutes of moderate activity a week, plus muscle-strengthening on two days.

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DriveMind

Habits are easier to repeat when the cue is obvious. Put the book, the trainers or the water bottle where you will see it, so you can start before your mood has time to argue.

Psychologists describe habits as a loop: a cue, such as a place, a time of day or the sight of an object, sets off a routine, and a reward makes it likelier to happen again. In diary studies from 2002, Wendy Wood's team found that about 43% of what people did each day was habitual, repeated almost daily in the same setting, often while their minds were elsewhere. A visible cue works because the action no longer depends on remembering it, or feeling like it, at the right moment.

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DriveMind

An “if-then” plan links a goal to a specific cue: “If X happens, I will do Y.” Across studies, people who make plans like this follow through more often, on average, than people who only set the goal.

Psychologists call these plans implementation intentions. The idea was developed in the 1990s by the German psychologist Peter Gollwitzer, who works at New York University and the University of Konstanz. In 2006 he and Paschal Sheeran pooled 94 separate tests involving more than 8,000 people and found that such plans had a medium-to-large effect on reaching goals. A well-known field test followed in 2011. Katherine Milkman and colleagues sent flu-jab reminders to employees of a large US company. Among those who were also asked to write down the date and time they planned to go, 37.3% got vaccinated, compared with 33.1% of those who received only the clinic details. Deciding when and where in advance lets the situation itself prompt the action, instead of relying on willpower in the moment.

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DriveMind

A new habit is easier to remember when it is attached to an existing cue: after coffee, after brushing teeth, after opening your laptop.

Psychologists call the familiar routine a cue. Habits form when the same action follows the same cue again and again, until the cue starts the behaviour almost by itself. From the 1990s the psychologist Peter Gollwitzer showed that people who make a specific if-then plan, such as ‘after I pour my coffee, I will stretch for two minutes’, carry out their goals more often than people who simply intend to. He called these plans implementation intentions. The Stanford researcher BJ Fogg calls the existing routine an anchor. Patience helps too. In a 2010 study at University College London, 96 volunteers repeated a new daily habit: half needed less than 66 days before it felt automatic and half needed more, with a range of 18 to 254 days.

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DriveMind

If the target feels too large to start, shrink the first action: one page, one minute, one message, one small piece you can actually do.

Why it works: in a 2007 review of hundreds of studies, the psychologist Piers Steel of the University of Calgary found that people put off a task most when it feels unpleasant and when they doubt they can do it. A tiny first step is less daunting and easy to succeed at. Progress then feeds motivation. Teresa Amabile and Steven Kramer of Harvard Business School read nearly 12,000 daily diary entries from people doing complex work and found that even small steps forward in meaningful work were the biggest single boost to their mood and motivation. They called this the progress principle.

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DriveMind

Neuroplasticity is the brain's ability to change with experience. It rarely happens overnight: each time you practise something, the connections between the nerve cells involved grow a little stronger, until what once felt hard starts to come more easily.

The idea goes back to the Canadian psychologist Donald Hebb, who proposed in 1949 that when one nerve cell repeatedly helps to fire another, the link between them grows stronger. It is often summed up as ‘cells that fire together wire together’. Brain scans later showed such change on a larger scale. A 2000 study found that London taxi drivers, who spend years learning the city's streets, had a larger rear part of the hippocampus, a region involved in finding the way, than people who did not drive taxis, and the difference grew with years in the job. In 2004 German researchers scanned volunteers before and after three months of learning to juggle: areas that process moving objects had grown slightly, and they shrank back once the practice stopped.

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StillnessHealth

Sleep is part of learning, not a pause from it: while you sleep, the brain goes back over what you practised during the day and strengthens it. That is why a new skill often runs more smoothly the next morning than it did the evening before.

In a 2002 study at Harvard Medical School, led by Matthew Walker, volunteers learned to type a short number sequence as quickly and accurately as they could. After a night's sleep they were about 20 per cent faster, with no loss of accuracy, while the same number of hours awake brought no significant gain. The size of the improvement was linked to how much light sleep, known as stage 2, people had, especially late in the night. Animal studies from the 1990s suggest how this might work: in rats, groups of brain cells that were active while the animals explored became active together again during sleep, as if the day were being replayed. It is one reason why an extra tired hour at the desk may help less than a full night's sleep.

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WonderMind

The human brain contains about 86 billion neurons, the nerve cells that carry signals, and roughly as many other cells that support them. Each neuron can connect with thousands of others. The figure comes from a 2009 study that counted the cells instead of estimating them.

For decades textbooks said the brain had 100 billion neurons and ten times as many support cells, called glia, but nobody had actually counted them. In 2009 the Brazilian neuroscientist Suzana Herculano-Houzel and colleagues in Rio de Janeiro used a method she had developed with Roberto Lent, the isotropic fractionator. Brain tissue is dissolved into an even liquid of cell nuclei; a small sample is counted under the microscope, with a stain that marks only neurons, and the result is scaled up. In adult men's brains they found about 86 billion neurons and 85 billion other cells, so the famous ten-to-one ratio was wrong. Another surprise: only about a fifth of the neurons sit in the cerebral cortex, the brain's wrinkled outer layer. Most are packed into the cerebellum, at the lower back of the brain.

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DriveMind

People usually remember material better when they study it in several sessions spread over time than when they pack the same hours into one sitting. This spacing effect, first measured by the German psychologist Hermann Ebbinghaus in 1885, is one of the most reliable findings in memory research.

Ebbinghaus experimented on himself. He learnt lists of meaningless syllables such as “WID” and “ZOF”, so that nothing he already knew could help, and recorded how many repetitions each list took. When he spread his repetitions over several days, he needed fewer in total than when he crammed them into one day. Later studies found the same pattern with words, facts, foreign vocabulary and physical skills. One explanation is that a review after a gap makes the brain work to recall something it has half forgotten, and that effort strengthens the memory; the psychologist Robert Bjork calls such useful struggles “desirable difficulties”. In 1972 the German science journalist Sebastian Leitner turned the idea into a box of flashcards reviewed at growing intervals, and today's flashcard apps work on the same principle.

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WonderMind

An adult brain weighs about 1.3 kg, roughly 2% of body weight, yet it uses about 20% of the energy the body burns at rest. Most of that energy pays for the brain's constant background activity, not for the extra effort of thinking hard.

The brain's main fuel is glucose, the sugar carried in the blood; during long fasts it can also run on ketones, which the liver makes from fat. Much of its energy powers tiny pumps that move charged particles in and out of nerve cells, keeping each one ready to send a signal. Brain scans by the American neurologist Marcus Raichle and others showed that a hard mental task raises the brain's total energy use only slightly, often by less than 5%, and he called the constant background activity the brain's “dark energy”. In most vertebrates the brain takes 2 to 8% of resting energy, so humans are unusual. The share peaks in early childhood: a 2014 study estimated that at about four years old the brain uses around two thirds of the body's resting energy.

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StillnessMind

Cyclic sighing, breathing in twice through the nose and then out slowly and fully, lifted mood more than mindfulness meditation in a 2023 Stanford study. Of four methods that 108 adults practised for five minutes a day for a month, it gave the biggest rise in good mood and the biggest drop in resting breathing rate.

The study was led by the psychiatrist David Spiegel and the neuroscientist Andrew Huberman and published in Cell Reports Medicine. Most volunteers came from an undergraduate psychology class at Stanford, and they were assigned to groups at random. The other breathing exercises were box breathing, with equal counts for breathing in, holding, breathing out and holding again, and cyclic hyperventilation, deep breaths in and short breaths out followed by holding the breath. In cyclic sighing the second, shorter breath tops up the lungs before the long exhale. A long, slow exhale is thought to calm the body through the vagus nerve, which slows the heart. People also sigh on their own every few minutes, which helps reopen tiny air sacs in the lungs. With about a hundred mostly young, healthy volunteers and one month of practice, the study is encouraging but small.

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DriveMind

Trying to recall what you have learnt, without looking, fixes it in memory better than reading it again. Psychologists call this the testing effect: each time you pull a fact out of memory, it becomes easier to find the next time.

The idea is old. Francis Bacon noted in 1620 that reading a text ten times while trying now and then to recite it teaches it better than reading it through twenty times, and William James made the same point in 1890. The best-known modern test came in 2006, when Henry Roediger and Jeffrey Karpicke at Washington University in St. Louis had students read short prose passages and then either reread them or write down all they could remember. Five minutes later the rereaders did better. Two days and a week later, the students who had practised recalling remembered clearly more, even though the rereaders felt more confident. Rereading feels easy because familiar text looks known, and that ease is easily mistaken for learning. Flashcards, practice questions and writing a summary on a blank page all use the same effect.

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DriveMind

When two tasks both need conscious attention, such as writing an email and following a conversation, the brain usually cannot do them truly at once. It switches back and forth, and each switch costs a little time and makes mistakes more likely. Psychologists call this the switch cost.

The cost was first measured in 1927 by the American psychologist Arthur Jersild, who timed people working through lists of numbers: lists on which they had to alternate between adding and subtracting took longer than lists with one operation all the way down. In 1995 Robert Rogers and Stephen Monsell showed that part of the cost remains even when people know a switch is coming and have time to prepare. It matters on the road. In a 2006 driving-simulator study at the University of Utah, drivers talking on a phone, handheld or hands-free, braked later and had more collisions than when they were not talking. Tasks that are well practised or use different senses, such as walking while chatting, get in each other's way far less, and the size of the cost depends on the tasks and the person.

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WonderMind

Dopamine, a chemical messenger in the brain, is central to motivation and learning. Its activity changes most when things turn out better or worse than expected, which helps the brain learn which cues are worth paying attention to.

The key experiments were made in the 1980s and 1990s by the neuroscientist Wolfram Schultz, then at the University of Fribourg in Switzerland, who recorded dopamine cells in monkeys. When a drop of juice arrived unexpectedly, the cells became active. Once a light or a sound reliably came before the juice, they responded to the signal instead and barely reacted to the juice itself. If the expected juice did not arrive, their activity dropped below normal. The cells were tracking the gap between what was expected and what happened, now called the reward prediction error, and some computer learning methods use a similar signal. This is how a phone's ping can become a cue that grabs attention: it hints that something interesting may be waiting. That is different from saying every notification gives everyone the same burst of pleasure.

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DriveMind

Spaced review works best when the gap between reviews fits how long you need to remember something. In a 2008 study of more than 1,350 people, the best gap before a review was about one to three days for a test a week later, and several weeks for a test a year later.

Psychologists including Nicholas Cepeda and Harold Pashler taught volunteers a set of facts, gave them a single review after a gap of up to three and a half months, and tested them up to a year later. Lengthening the gap helped at first, then slowly began to hurt. As a share of the time until the test, the best gap shrank from about 20 to 40% for a one-week wait to about 5 to 10% for a one-year wait. The study followed a 2006 review by the same team that pooled 317 experiments. Timing matters because we forget fastest in the first hours and days after learning, the decline Hermann Ebbinghaus plotted in 1885 as the forgetting curve, and a well-timed review slows it down.

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DriveMind

Learning a skill can change the brain's structure, including its white matter: the bundles of nerve fibres wrapped in myelin, a fatty coating that speeds up signals. How much of this change comes from new myelin is still being worked out.

In the brain and spinal cord, myelin is made by cells called oligodendrocytes, which wrap layer upon layer of membrane around nerve fibres; the fatty wrapping makes the fibres look pale, hence “white matter”. In 2009 researchers at Oxford scanned 24 adults before and after six weeks of learning to juggle and found a change in the white matter under an area near the top and back of the brain that links vision and movement; a comparison group who did not train showed no such change. Brain scans cannot see myelin directly, so the strongest evidence comes from animals. In 2014 a team at University College London showed that mice learning to run on a wheel with irregularly spaced rungs made new oligodendrocytes, and that mice unable to make them failed to master the wheel.

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WonderMind

The default mode network is a set of brain regions that becomes more active when the mind turns inward, to memories, plans or other people, and quietens during many tasks that need attention on the outside world.

The idea that the brain stays busy at rest goes back to Hans Berger, inventor of the EEG, which records the brain's electrical activity through the scalp. In 1929 he reported that these rhythms continue when a person is doing nothing. In the 1990s PET scans, which track blood flow and energy use, showed that the same set of regions reliably became less active when volunteers started a task, and in 2001 the American neurologist Marcus Raichle named this pattern the brain's “default mode”. The network's main hubs lie along the midline of the brain, at the front and towards the back. It is involved in recalling your own past, imagining the future and thinking about what others feel. In Alzheimer's disease its regions use less energy, and amyloid plaques, clumps of a sticky protein typical of the disease, build up there even before symptoms appear.

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WonderMind

Working memory, the mental space where you hold information for a few seconds while using it, is smaller than the famous “seven items” suggests. When people cannot group or rehearse items, most experiments find room for only about three or four at once.

The number seven comes from a 1956 paper by the American psychologist George Miller, “The Magical Number Seven, Plus or Minus Two”, which noted that people can repeat back about seven digits. Digits, though, can be grouped and silently rehearsed. In 2001 the psychologist Nelson Cowan reviewed experiments that blocked such tricks and concluded that the real limit is about four “chunks”. A chunk is any unit you already know, so grouping, or chunking, stretches capacity: “BBC NHS FBI” is three chunks, not nine letters. Chess masters can remember a real game position after a glance but lose most of their advantage when the pieces are placed at random. In one famous experiment, a student who was a long-distance runner raised his digit span from seven to about 80 by recoding strings of digits as race times.

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WonderMind

Cognitive reserve is the idea that education, mentally demanding work and a lifetime of learning may help some people keep thinking clearly despite ageing or brain disease. Two people with similar brain damage can show very different symptoms.

The idea took shape after a 1988 study led by the American neurologist Robert Katzman, which examined the brains of 137 nursing-home residents after death. Ten had plaques typical of Alzheimer's disease, yet in life they had been among the best performers on memory and thinking tests, and their brains were heavier and held more nerve cells than those of their peers. The neuropsychologist Yaakov Stern later developed the concept, arguing that education and mental activity help the brain cope with damage by using its networks more efficiently or finding other routes. The 2024 report of the Lancet Commission on dementia lists less education in early life among 14 risk factors that can be changed. Bilingualism has also been proposed as a source of reserve, but studies disagree, so speaking two languages is not a proven protection.

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DriveMind

A single session of aerobic exercise, such as a brisk run or bike ride, can raise blood levels of BDNF, a protein that helps nerve cells survive, grow and form new connections. The rise is temporary, and its size varies from person to person.

BDNF stands for brain-derived neurotrophic factor. Yves-Alain Barde and Hans Thoenen first isolated it from pig brain in 1982, and it is especially active in the hippocampus, a region central to learning and memory. In 1995 Carl Cotman's team at the University of California, Irvine found that rats given running wheels made more BDNF in the hippocampus. In people, a 2017 analysis of 55 studies found that blood BDNF was higher after a single session of exercise, with longer sessions giving bigger rises; the effect was clear in men but not in women. Blood levels are only an indirect guide to what happens inside the brain. The findings support a link between exercise and plasticity, the brain's ability to change, without proving that BDNF explains the clear-headed feeling after a walk.

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StillnessMind

Putting a feeling into words can quieten the brain's alarm system. In a 2007 brain-scanning study at UCLA, when people chose a word for the emotion on an angry or frightened face, the amygdala, the brain's threat detector, responded less than when they described the faces in other ways.

The study, led by the psychologist Matthew Lieberman and published in Psychological Science, offered brain evidence for something therapists have long encouraged: putting feelings into words, which researchers call affect labelling. The amygdala reacts quickly to possible danger. Labelling also raised activity in the right ventrolateral prefrontal cortex, a frontal area linked to controlling emotions, and the more it rose, the more the amygdala's activity fell. In 2012 a UCLA team tried the idea on people afraid of spiders. Those who described their feelings aloud while facing a live spider showed less physical arousal, measured by sweat on the skin, when they met a different spider a week later than those who used other strategies, although they did not report feeling less afraid. Naming a feeling is no cure for anxiety, but it seems to change how the brain handles it.

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DriveMind

The Swedish psychologist Anders Ericsson showed that experts improve through deliberate practice: focused work on specific weaknesses, usually with a teacher's feedback. The popular “10,000-hour rule” came later, as a simplification of his work; he never claimed it was a threshold everyone must cross.

The rule traces back to Ericsson's 1993 study of violinists at a music academy in Berlin. By the age of 20 the best students had practised alone for about 10,000 hours on average, more than less accomplished students. In his 2008 book Outliers, the journalist Malcolm Gladwell turned that average into a rule. Ericsson objected: the figure was an average, not a threshold; the violinists were still far from masters at 20; the hours needed differ between fields; and only focused practice aimed at improving counts, not every hour spent playing. Practice matters, but later research found its weight varies. A 2014 meta-analysis, which pools the results of many studies, found it explained around a quarter of the differences in performance in games, about a fifth in music and very little in professional work.

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StillnessMind

Losing sleep reliably weakens alertness and attention, and it can also impair judgement, impulse control and control of emotions. People are often poor judges of how impaired they are.

Much of the evidence comes from simple tests of sustained attention, such as pressing a button whenever a light appears at random, which reveal lapses and microsleeps, moments of sleep lasting a few seconds. In a 2003 study at the University of Pennsylvania, volunteers who slept six hours a night for two weeks ended up doing as badly on such tests as people kept awake for up to two nights, yet they rated themselves only slightly sleepy. In a 2000 Australian study, 17 to 19 hours without sleep left performance on some tests as poor as at a blood alcohol level of 0.05%, the drink-driving limit in much of Europe. Emotions suffer too: after a night without sleep, the amygdala, the brain's threat detector, reacts more strongly to unpleasant pictures and is less restrained by the front of the brain.

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WonderMind

Negativity bias is the tendency to give threats, losses and criticism more attention and weight than equally strong good news. It is why one harsh comment can stay with you longer than several kind ones.

The term was popularised by an influential 2001 paper by the psychologists Paul Rozin and Edward Royzman at the University of Pennsylvania. The same year, Roy Baumeister and colleagues published a review titled “Bad Is Stronger Than Good”, which found the pattern in first impressions, relationships, feedback and memory. In experiments, people are slower to name the ink colour of a negative word than of a positive one, a sign that bad news holds attention. Daniel Kahneman and Amos Tversky found a related effect with money: losing a sum feels roughly twice as strong as gaining it. A common explanation is evolutionary, since missing a danger costs more than missing a chance. Precise ratios deserve doubt, though. A famous claim that people need 2.9 good feelings for every bad one was shown in 2013 to rest on flawed mathematics.

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