Babies can be More Altruistic than Adults

A new study shows that most toddlers will help a stranger, even if it means giving up a delicious treat.


By Susan Pinker

Toddlers are innocent and sweet, but are they good? Pint-sized autocrats who wake up at dawn, expect food and drink on demand, say no to everything, and who can kick, scream and bite if they don’t get their way are called Terrible Twos for a reason.

A new study tells a different story. Published recently in the journal Nature’s Scientific Reports, it shows that toddlers will offer up food they really want to a needy stranger. Most adults don’t show that kind of altruism.

The researchers, led by University of Washington post-doctoral scholar Rodolfo Cortes Barragan, made that discovery by testing 96 toddlers. In the first experiment, the child met an adult who was sitting behind a desk. (The desk was gated and the toddler stayed on the other side with a parent nearby, so they wouldn’t feel threatened.) The adult selected a piece of freshly cut strawberry, banana, blueberry or grape, which then suddenly slipped out of his hand and landed on a tray on the child’s side of the desk.

In the “begging experimenter” group, the adult acted dismayed, grasping the air impotently to get at the fruit. “He reaches for the yummy fruit, expresses the desire for it, but can’t get to it,” explained Andrew Meltzoff, one of the authors of the paper and the co-director of the University of Washington’s Institute for Learning & Brain Sciences. In contrast, the control-group adult nonchalantly tossed the fruit onto the tray.

There was a clear difference in the toddlers’ reactions. In the begging experimenter group, almost 60% of them retrieved the fruit and promptly offered it to the experimenter. In the control group only 4% did the same.

The second experiment raised the stakes by asking parents to bring their children to the lab when they were hungry. In this case, though more of the toddlers in the “begging experimenter” group gave in to their urges and ate the fruit, about 38% of them still handed it over to the stranger. “They would pick up the banana, look at the banana and hover over it. Some hungry children would even bring it to their mouths,” said Prof. Meltzoff. “Though there’s a biological push to act selfishly, there’s a social motivation to give it to the begging stranger,” he said. That social motivation evaporated when the hungry toddlers in the control group saw the experimenter intentionally toss the fruit away: 0% of those babies gave it back.

The knack for reading others’ needs and being motivated to help fulfill them is a distinctly human trait. “Chimpanzees don’t give up food to a stranger,” said Dr. Cortes Barragan. Mother chimps won’t even offer prized bits of fruit to their own toddlers, according to a 2004 study. They eat the best morsels themselves and leave the stems and seeds for the babies. (For their part, toddler chimps just grab a dropped chunk of fruit and run with it.)

There are evolutionary reasons why human babies behave altruistically. By sharing food with strangers, they help to cement bonds with non-family members that hold the group together. But altruistic instincts can also be enhanced by experience, said Prof. Meltzoff. In this study, for instance, the fruit-sharers were slightly more likely to have siblings, and Asian and Latino babies shared more often than those from other backgrounds. “The value of interdependence is picked up by prelinguistic babies,” he said.

Prof. Meltzoff has now spent decades studying how infants grasp others’ intentions. But discovering that hungry babies will give up treats to a stranger still astonishes him. “These are young human beings, not even speaking in sentences. Yet they care about others and act altruistically toward them. We think babies are selfish, egocentric and a slave to their biological needs. But this study shows they’re not selfish. They’re social!”

Humans and Other Dancing Animals

A new study shows that chimps can move to a musical beat, suggesting that primates have danced for millions of years

By Susan Pinker

Most of us have heard of dancing bears or dogs that can do the samba. But those animals are trained to perform; none of our animal friends can spontaneously cut a rug. Or so I thought.

Now a study published in Proceedings of the National Academy of Sciences shows that chimpanzees exposed to electronic music will sway along with the beat. Like us, they are better at matching their moves to the music when they are standing, as opposed to sitting or crouching on all fours. But make no mistake, these chimps move in a way that looks an awful lot like dancing: “The chimpanzees mostly swayed their whole body, but rhythmic movements of body parts such as hand clapping or foot tapping were also observed,” the study reports.

Pan troglodytes, to use the scientific name for chimps, is one of our closest evolutionary ancestors. They have previously been known to bang rhythmically on tree trunks and to hoot and call to each other in a way that sounds like call-and-response singing. But the observation that chimps can move their bodies in time to music is new. It suggests that dancing has existed in higher-level primates—a group that would include us humans—for at least six million years. That’s roughly how long ago humans split off from other higher apes, like chimps.

The authors of the new study—Yuko Hattori, a researcher at the Kyoto University Primate Research Institute, and Masaki Tomonaga, a professor of language and intelligence there—discovered this rhythmic ability by playing two-minute audio clips to seven chimps in their lab. The music sounds like a series of thrumming bass chords played on an electronic piano. The cadence and tempo of the recordings changed at regular intervals so that the researchers could assess whether the chimpanzees could sync their movements to what they were hearing.

Though the chimps in this study seemed like they were grooving to the beat, not all primatologists would call that dancing. “It depends on what is meant by dancing,” according to Richard Wrangham, a Harvard University anthropologist who is an authority on chimpanzees. “Jane Goodall called the male group displays given at the onset of rain or heavy wind ‘rain dances,’ but that seems an exaggerated use of the term,” he told me in an email. “I have seen horses and hartebeest respond to heavy rain by galloping about. The more conservative view that I prefer is that the capacity for dancing is more than six million years old.”

That capacity has been observed in other species too, like sea lions, bonobos and parrots. In fact, members of the parrot family, like budgies and cockatoos, are even better at syncing their movements to a beat than chimpanzees are, wrote Dr. Hattori.

Take Snowball the cockatoo, whose fancy footwork, timed to Queen’s “Another One Bites the Dust,” has become clickbait. After Harvard psychologist Aniruddh Patel saw videos of Snowball on YouTube, he decided to investigate. Given that parrots are superb mimics, could Snowball have been imitating someone outside the frame? Or was he trained to dance?

The answer to both questions was no: Snowball was independently bobbing his head and high-stepping to the song. Like Akira, the best dancer in the chimpanzee study, his brain seems wired for music. Clearly, our human brains also have evolved to sway, shimmy and shake our bodies along to music. But so far, anyway, we’re the only ones who know the words and can sing along.

New Evidence for the Power of Grit

A study of West Point cadets shows that perseverance is just as important to success as brains or brawn

West Point cadets in basic training in 2006. PHOTO: KATE KARWAN BURGESS/ZREPORTAGE.COM/ZUMA PRESS

When I think of grit, a childhood friend comes to mind. Six of us neighborhood girls walked to school together, but it was Linda who bore the brunt of the boys’ snowballs. Once there she faced bigger hurdles: Every week our third-grade teacher made her circle the classroom with a failed test pinned to her tunic. Still, Linda pushed on, not just at age 8 but for years, until she earned a Ph.D. in English.

This kind of perseverance is a necessary ingredient of success, according to Angela Duckworth, a University of Pennsylvania psychologist who calls it “grit.”

In 2007, Dr. Duckworth and three colleagues published a paper in the Journal of Personality and Social Psychology, showing that a brief questionnaire measuring grit could predict who would succeed in tough environments such as military academies, Ivy League schools and even high-stakes spelling bees. Prof. Duckworth and her team later extended the findings, showing that grittier people are more likely to stay the course in long-haul commitments such as marriage.

In every study, the researchers had benchmarks showing how gritty each participant was compared to the norm, based on their performance on the 12-item Grit Scale. Developed by Prof. Duckworth, the scale includes statements such as “Setbacks don’t discourage me” and “I often set a goal but later choose to pursue a different one.” Each participant responded with one of five graded answers, from “very much like me” to “not like me at all.”

Still, some questions remained. Would the evidence about grit survive replication? Over the last decade, a slew of viscerally appealing findings published in top psychology journals couldn’t be reproduced when the same experiments were repeated with greater rigor or larger samples. So Prof. Duckworth and her colleagues at West Point and Duke University decided to redo one aspect of their first experiment using a sample seven times as large as the original, in a recent study published in the Proceedings of the National Academy of Sciences. Nine cohorts comprising 11,258 cadets at West Point were assessed on their levels of grit, academic achievement and physical prowess, with the tests being repeated as the students progressed through college.

The replication was reassuring. “Our original finding was that grit was an extraordinarily strong predictor of who would finish the initial period of training,” Prof. Duckworth said, referring to the punishing six-week initiation period the military cadets call Beast Barracks, or Beast for short. “That replicated,” she said.

Hard work and determination are important, but do they outweigh natural smarts or athletic prowess?

The second question posed by this new study: How does grit relate to other traits, like talent? Hard work and determination are important, to be sure, but do they outweigh natural smarts or athletic prowess?

The researchers measured grit, academic achievement and physical ability, and discovered that “the three factors really are distinct,” Prof. Duckworth said. “The grittier people are not necessarily more able.” And the cognitively able did not have more grit, nor were they more physically adept. In fact, the opposite was true: When one trait went up, the other went down. Students with stratospheric levels of intelligence or physical prowess were less gritty, and thus somewhat less likely to graduate. At the high end of brains and brawn, completion rates dropped off—a paradox that merits its own study.

But overall, the most powerful forecast of a student’s grades at West Point was cognitive ability as assessed by standardized tests, a finding that confirms 100 years of intelligence research. “That’s what predicted military GPA,” Prof. Duckworth said. “Cognitive ability is being smart. It’s not hard to understand how that might help you with military strategy.” In other words, it’s the gritty folks who finish what they start. But it’s the smart ones who go to the top of the class.

Time Pressure Can Squeeze the Truth

A new study shows that quick responses to questions tend to be less honest than more deliberate ones.


By Susan Pinker

Oct. 31, 2019 4:21 pm ET

The idea that we have two minds, an authentic inner core and a false outer layer, is as ancient as Plato and as current as the new hit movie “Joker. ” If our real identities are packed away, hidden even from ourselves, we seldom reveal what we really think and instead cultivate appearances—or so many psychologists believe. According to this view, the best way to get people to tell the truth is by eliciting lightning-quick responses, before they can reflect and dissemble.

But this may not be so, says a study published last month in the journal Psychological Science. It found that people are more likely to lie about themselves when under time pressure. “Asking people to respond quickly just makes them give you the answer you want to hear,” said John Protzko, the study’s first author and a postdoctoral scholar at the University of California, Santa Barbara.


How do you know when someone’s lying to you? Join the conversation below.

This finding, now replicated five times (twice by Dr. Protzko’s team, three times by independent labs), could undermine one of the bedrock assumptions of pop psychology: that speedy responses, like those described in Malcolm Gladwell’s 2005 book “Blink,” can provide access to our hidden brains.

To test that notion, Dr. Protzko’s team randomly assigned 1,500 representative Americans to one of two groups. The “fast group” had to answer each of 10 questions within an 11-second time limit. The “slow group” got more time to reflect, as they had to wait at least 11 seconds before responding.

Both groups were given the same survey, a standardized test called the Social Desirability Scale, which measures the degree to which people describe themselves in socially acceptable terms. The scale includes personal statements such as “There have been times when I was quite jealous of the good fortune of others” and “I have never intensely disliked anyone.” By comparing an individual’s responses to these statements with the statistical average, researchers can capture how likely it is that they are fudging the truth to enhance their reputation.

Responses to these categorical statements were revealing. We expect people to show their hidden cards when buttonholed for a quick reaction. But the study found that we are about 30% more likely to lie about ourselves when rushed to respond. This result makes sense: In human societies, tit-for-tat-type exchanges grease the wheels of interpersonal interaction. Enhancing our reputations by presenting ourselves in the best possible light is the natural, quick and easy thing to do.

By contrast, defying social norms by admitting our faults takes not only more deliberation but also a more relaxed context—one often lacking in psychological research. People are more motivated to tell the unvarnished truth in non-judgmental environments than in the typical cinder-block, fluorescent-lit psychology lab, with a stopwatch ticking. If experimental psychology hopes to capture our true, unamplified selves, it may have to reproduce environments and time-frames that allow us to let our guard down.

As Dr. Protzko observed, many studies “assume that putting people under time pressure gives you access to a hidden part of the mind. But we’re finding that they’re just lying. They’re giving you the answer that makes them look best.” He adds, “When you make people answer quickly, everyone lies.”

The moral of the study? If you want the truth, you have to be willing to wait for it.

Pessimism about Social Mobility


By Susan Pinker

The expectation that every generation will be better educated, earn more and live in a nicer home than their parents is the essence of the American dream. The formula largely worked for Americans in the 19th and 20th centuries. Do we still expect it to? A paper published this summer in the Proceedings of the National Academy of Sciences set out to answer that question.

“I study how children are doing in relation to their parents,” said sociologist Siwei Cheng of New York University, the study’s lead author. “And America is not doing that well, compared to other Western countries.” In Canada, for instance, the chances of a low-income child entering the middle class are twice as great as they are in the U.S. The question that Prof. Cheng sought to answer is whether Americans still believe in the American dream. “Are Americans really that optimistic about mobility?”

Prof. Cheng and Fangqi Wen, a postdoctoral fellow at the University of Oxford, polled the attitudes of 3,077 American adults. Each participant was asked to consider the prospects of a child whose family’s income was in a specific percentile, compared to all American families. A computer spat out a randomly generated income rank, and the participant would estimate how much a child growing up in such a family would earn as a 40-year-old. The next step was to compare subjects’ perceptions to what up-to-date tax data tell us about the actual earnings of someone from such a family.

Americans underestimate the future earnings of children from poor families and overestimate the future earnings of children from middle and upper class families.

This comparison revealed a disconnect: Americans underestimate the future earnings of children from poor families and overestimate the future earnings of children from middle and upper class families. “The reality is that there is indeed a [mobility] gap, by international standards. But what people have in their mind is a larger gap, in terms of how rich and poor kids will do. They’re pessimistic about equality of opportunity,” said Prof. Cheng. To be precise, “the American public perceives the gap in economic outcomes between children from rich and poor families to be twice as large as it actually is.”

The researchers also discovered some surprising demographic divides. College-educated adults estimated a larger opportunity gap than those without a degree. Liberals were more pessimistic than conservatives, younger people more pessimistic than those over 30, and those earning between $30,000 and $100,000 a year more pessimistic than everyone else. In other words, middle-class, educated Americans see less reason for hope about social mobility than the rest of the population.

So much for the American dream.

The study doesn’t try to identify the sources of this pessimism, but we can hazard some guesses. It could be that the squeeze on middle-class jobs and incomes over the past generation has undermined middle-class faith in advancement. In addition, the suspicion of inequality in American society may lead people to assume that the children of the wealthy are getting a free pass, while the children of the poor must be even more hobbled by their reduced chances.

Whatever the reason, if Americans no longer believe that children who start near the bottom can make it to the top—or even to the middle—a good first step is to reconcile our attitudes with the data. There is more upward mobility in America than most of us think, but unless we want to start calling it the Canadian dream, there’s still a long way to go.




When Taking Risks Is the Best Strategy

Research on fishing fleets shows that in the face of scarce resources, trying new approaches can bring big rewards


One way to divide up the world is between people who like to explore new possibilities and those who stick to the tried and true. In fact, the tension between betting on a sure thing and taking a chance that something unexpected and wonderful might happen bedevils human and nonhuman animals alike.

Take songbirds, for example. The half-dozen finches perching at my deck feeder all summer know exactly what they’ll find there: black sunflower seed, and lots of it. Meanwhile, the warblers exploring the woods nearby don’t depend on this predictable food source in fine weather. As foragers, they enjoy other advantages: a more varied diet, less exposure to predators and, as a bonus, the chance to meet the perfect mate flitting from tree to tree.

This “explore-exploit” trade-off has prompted scores of lab studies, computer simulations and algorithms, trying to determine which strategy yields the greatest reward. Now a new study of human behavior in the real world, published last month in Nature Communications, shows that in good times, there’s not much difference between pursuing novelty and sticking to the status quo. When times are tough, however, explorers are the winners.

The new study, led by Shay O’Farrell and James Sanchirico, both of the University of California, Davis, along with Orr Spiegel of Tel Aviv University, examined the routes and results of nearly 2,500 commercial fishing trips in the Gulf of Mexico over a period of 2½ years. The study focused on “bottom longline” fishing, a system where hundreds of lines are attached to a horizontal bar that is then lowered to reach the sea bed. Dr. O’Farrell explained the procedure this way: “Go to a location and put the line down. Stay for a few hours. The lines are a mile long and have a buoy at either end. When they pull that up, they assess the catch, then decide if they will stay or move on to a different spot.”

Over two years of collecting data under various climate conditions, the researchers discovered that the fishermen were fairly consistent. “The exploiters would go to a smaller set of locations over and over, and go with what they know,” Dr. O’Farrell said. “The explorers would consistently try a wider range; they’d sample new places.”

The payoffs were clear. The explorers benefited from their prior knowledge of alternatives—and their ability to take risks—when the going got tough. For instance, while the study was under way, some prime fishing grounds were unexpectedly closed to protect their population of endangered sea turtles. Those who explored alternative sites had other options when their usual fishing grounds were suddenly off limits. Unlike the exploiters, “they didn’t have to start from ground zero to gain the knowledge they needed” when conditions changed, said Dr. O’Farrell. At the very least, they were more likely to continue to fish during an upheaval.

Similarly, the immediate impact of storms didn’t disrupt the explorers as much as it did those who cleaved to their routine. In the long run, there wasn’t a huge difference between the two groups, perhaps due to the sharing of information between fishing crews, said Dr. O’Farrell. But in challenging times, the study’s message was clear: “You can try new things in the face of uncertainty.”

Bystanders who Intervene in an Attack

In 1964, the Kitty Genovese case taught the world that strangers wouldn’t come to a victim’s aid. New research suggests that, in fact, they usually do.


If you were assaulted in a public place, do you think anyone would intervene? Or would they just look down at their shoes and walk on by?

Most people expect very little help from strangers, especially in the big cities to which vast populations in the modern world have migrated over the past century. Having once lived overwhelmingly in far-flung rural hamlets, Americans have long seen cities as anonymous, dangerous places.

In 1964, the fatal stabbing of Kitty Genovese made this sense of threat more palpable. Genovese, a 28-year-old woman returning from a night shift, was brutally attacked in the entrance of her Queens, N.Y. apartment building. Thirty-eight of her neighbors purportedly heard her screams and did nothing to help. Her story launched a new psychological term: the Bystander Effect, which refers to the idea that the greater the number of bystanders, the less likely people are to act as good Samaritans.

But there was a problem with both the term and the story. Many of the details of the Kitty Genovese story turned out to be false. She did die at the hands of a violent stranger, but subsequent sleuthing revealed that several bystanders did, in fact, try to intervene. And a study published last month in the journal American Psychologist confirms that bystanders aren’t as passive as we once thought. Not only will an observer often step forward in a real crisis, but the more people are present, the more likely the victim is to get assistance.

“It only takes one person to help the victim,” said Richard Philpot, the paper’s first author and a research fellow in psychology at Lancaster University and the University of Copenhagen. Working with three colleagues, Dr. Philpot broke away from previous approaches to documenting the Bystander Effect. Instead of simulating a violent emergency while groups of various sizes looked on, this new study analyzed closed circuit TV footage of real people interacting in public spaces.

In other words, Dr. Philpot’s team focused on genuine conflict—ranging from animated disagreement to physical violence—that spontaneously arose in public places in Amsterdam, Cape Town and Lancaster, U.K.

Four trained coders pored over footage from these cities’ surveillance cameras, culling 219 aggressive incidents from 1,225 video clips. The coders looked at the size of the crowd and zeroed in on any effort to calm the aggressor, to block contact between the two parties or pull the aggressor away, or to provide practical help to the victim.

What emerged was surprising, in more ways than one. Strangers intervened in nine out of 10 violent incidents. And the more people were around, the more likely it was that someone in trouble would get help. The consistency of the findings was remarkable: “South Africa was the only place were we saw weapons such as machetes, axes or knives,” said Dr. Philpot. “But victims were equally likely to be helped in conflicts there as they would be in the U.K. or the Netherlands.”

Some questions remain: How do people know when it’s safe to intervene, and would these findings hold in less populated places? But the new study is reassuring, at least for city-dwellers. There is indeed strength in numbers. It’s too late for Kitty Genovese, but there’s still time for the rest of us, who could be that one person in a crowd who steps forward to help.


Envy at its Worst: In the Future Tense

A new study shows that we’re more jealous of our friends’ plans and prospects than their past accomplishments.


It is better to be envied than to be pitied, wrote the Greek historian Herodotus, and in our use of social media it’s clear that most of us agree. After all, why post selfies of yourself and your sweetheart lifting champagne flutes en route to Thailand if not to induce an eat-your-heart-out response in your friends?

Ubiquitous public displays of everyone’s happy moments—with the low points edited out—are one reason, according to a 2017 study, that most of us believe other people lead richer social lives than we do. Research shows that most of us think we are better looking, smarter, more competent and of course less biased than other people. But our perspectives do a 180 when it comes to our social lives.

When we hear about our friends’ plans to share a summer cottage on the seashore, for example, we may feel green with envy. We imagine that they’ll have a blast—the group dinners on the screened-in porch, swimming together at the pond, the bike rides to get ice cream. The idyllic possibilities are enough to make a working stiff with one week of holiday gag.

Now a new study, published last month in the journal Psychological Science, adds a counterintuitive twist to this familiar story: Other people’s plans for the future irritate us much more than experiences they’ve had in the past. At first this idea might seem strange. Don’t we feel envy for people’s accomplishments and possessions, such as their expensive cars? We do, but the study shows that jealousy stings even more when we think about the good things that lie in their future. In fact, our envious feelings ramp up as someone else’s fortunate occasion gets closer—and plummet once the event is over. Apparently envy is time-stamped, like an email or a tray of raw chicken from the supermarket.

In the study, researchers asked 620 participants to imagine their best friend in each of five circumstances: on a dream vacation, a dream date or in the ideal job, car or house. To make the exercise more personal, the participants were asked for the initials of their best friend. Then they had to rate, on a scale of 1 to 7, how they would feel during the days and weeks leading up to each drool-worthy event, as well as the days and weeks that followed. “Imagine the 10 days and nights of your friend in Maui next month. How do you feel about this?” said Ed O’Brien, one of the study’s lead authors and a professor at the University of Chicago. “Now roll back a year. How does the trip make you feel now?”

The researchers discovered that envy includes negative emotions, like malice, but can also be a source of positive feelings, like increased motivation. Each feeling has its own timetable: “While negative reactions decrease over time once the friend has achieved something we want, time has no effect on the positive form of envy, the motivation to try to do that sort of thing in the future,” explained Prof. O’Brien.

The finding that envy is more predictably triggered by other people’s future prospects than by their past achievements fits into a larger argument. The human brain evolved to have an emotional bias toward the future. according to American social psychologist Roy Baumeister and his colleagues. First we focus on what we want, and then a second, more cautious stage of thinking comes into play so we can figure out what we must do to get it.

So if we want a kinder social media world, we should stick to posting about events that have come and gone, rather than inciting envy with things we’re looking forward to. Got plans for a long, lazy summer frolicking with friends at the beach? For now, you might want to keep that to yourself.

Pollution that Discriminates by Gender

A new study shows that boys’ brains are more vulnerable than girls’ to lead exposure in early childhood


While in Australia last month I learned that female green sea turtles on the Great Barrier Reef now outnumber males by 116 to 1. Biologists blame it on the rising temperature of the sand on Australian nesting beaches: The warmer the sand, the more females hatch. In Sarnia, Ontario—known as Chemical Valley due to its 36 local petrochemical plants—emissions and runoff have halved the number of boys born in the area since the early 1990s, according to studies published in Environmental Health Perspectives.

Now a new study, published online last month in the journal Economics and Human Biology, shows that U.S. counties where lead in the topsoil exceeds the national average had twice the number of five-year-old boys with long-term cognitive problems. Five-year-old girls weren’t affected. Right from conception, it seems that environmental stress, especially pollution, discriminates on the basis of sex.

Edson Severnini, a professor of economics and public policy at Carnegie Mellon University, and his colleagues Karen Clay and Margarita Portnykh began with the United States Geological Survey’s recorded levels of lead in topsoil in 252 of the largest counties in the U.S. in 2000. They then turned to parents’ responses to a question on the 2000 census: Had their five-year-old experienced difficulties, for at least six months, with learning, memory, focus or decision making? The parents of over 77,000 children replied with a yes or a no.

We’ve long known lead to be dangerous, and adding the heavy metal to gasoline, house paint and pesticide has been banned now for decades. Nonetheless, we’re still living with lead’s legacy. Over the 20th century more than 6.5 million tons were released into the environment across the U.S., most of it still blowing around or sticking to soil particles. That is alarming because lead is a neurotoxin: It starves the brain—especially the frontal lobe of the developing brain—of protein and energy, and it doesn’t decompose.

To make matters worse, lead on painted windowsills and in garden soil tastes sugary. Innocently ingesting even tiny amounts of lead can translate to lower IQs and attentional and behavioral problems later on, researchers have found.

There is even evidence that higher levels of lead in the bloodstream can predict antisocial behavior and violence in adolescence and early adulthood, according to a 2012 study led by Tulane medical researcher Howard Mielke published in the journal Environment International.

The new Carnegie Mellon study reinforces the link between a child’s early lead exposure and an uncertain future. Preschoolers’ exposure to lead in their first five years of life increased their probability of compromised cognitive function, including a weaker ability to learn, solve problems and control one’s impulses. The study also adds two fascinating twists to the existing mound of scary data: Boys are twice as vulnerable as girls to early neural damage, and even levels of lead that are currently considered acceptable can exert a deleterious effect.

Our problems with lead aren’t history, this study shows. But it turns out that education can dampen lead’s harmful effects. “We actually show that if boys had some schooling, the [negative] effect was much smaller,” said Dr. Severnini. Except for restricting the lead in small aircraft fuel, which is still unregulated, and remediating contaminated soil where children live and play, we may not be able to control how much lead is still hanging around. But there is something we can do to protect our children’s brains, and it is called preschool



Women Have Younger Brains than Men

A new study of brain metabolism reveals a gender gap with important implications for the way we age


Women tend to live longer than men. This is one of the most robust findings in biological science, and the evidence isn’t hard to find. In the U.S., women outlive men by almost five years, on average, while the gap is as wide as 10 years in Latvia and Vietnam. Now there is fresh evidence that women not only have a longevity advantage; their brains seem to be more youthful throughout adulthood, too.

The new study, published last month in the Proceedings of the National Academy of Science, was led by radiologist Manu Goyal and neurologist Marcus Raichle, both at the Washington University School of Medicine. It shows that, when measuring brain metabolism—that is, the rate at which it uses glucose and oxygen to power its energy-hungry activities—the brains of adult women consistently appear about three years younger than men’s brains do. This brain-age gender gap mirrors the difference in longevity, and it may tell us something important about how sex differences in neural development affect how long we keep our marbles—and, ultimately, how long we live.

In the early 1970s, Dr. Raichle was one of the first neuroscientists to use PET scans to look at cognitive function in a living person’s brain. Now 82, he is still at it. In this study, the Goyal-Raichle research team deployed PET scans to assess how much energy is consumed by an adult’s brain and exactly where in the brain the demand is greatest. “Glucose is like coal. It burns up in the brain and produces energy,” Dr. Raichle said. “But when you burn up things in the brain you produce byproducts that the brain doesn’t want hanging around,” he explained. Glucose makes energy and also does the mopping up afterward. Thus, how much glucose is used to power the brain’s daily activities, including its cleanup functions, will tell you something about how vigorous and youthful that brain is.

In the new study, 205 healthy adults between the ages of 20 and 82 underwent PET scans while lying quietly in the scanner with their eyes closed. The researchers used the scans to assess blood flow to various neural regions, and also to track two forms of glucose uptake: one that burns oxygen (oxydative) and one that doesn’t (non-oxydative). Based on a study they published in 2017, the researchers already knew that our brains use glucose in both ways when we’re young, but that non-oxydative glucose consumption takes a nose dive as we age. They also knew that, after puberty, blood flow in the brain declines less in women than it does in men.

These persisting gender differences in brain metabolism meant that women’s brains often looked younger than those of men their age. The researchers used machine learning to detect distinctive patterns in the brains they studied. “When we trained it on males and tested it on females, then it guessed the female’s brain age to be three to four years younger than the women’s chronological age,” said Dr. Goyal. Conversely, when the machine was trained to see female metabolic patterns as the standard, it guessed men’s brains to be two to three years older than they actually were. That difference in metabolic brain age added up to approximately a three year advantage for women.

These brain age differences persisted across the adult lifespan and were visible even when people’s brains showed the harbingers of Alzheimer’s disease. “These new findings provide yet more evidence, as if more were needed, of just how ubiquitous sex influences on brain function have proven to be, often showing up in places we least expect them,” said Larry Cahill, a neuroscientist who studies sex differences in the brain at University of California, Irvine. “The fact that we often struggle to understand what they mean—as happens in the rest of neuroscience—does not make them less important.”