How Children Succeed: Grit, Curiosity, and the Hidden Power of Character (7 page)

9. LG

Much of the new information about childhood and poverty uncovered by psychologists and neuroscientists can be daunting to anyone trying to improve outcomes for disadvantaged children. We now know that early stress and adversity can literally get under a child’s skin, where it can cause damage that lasts a lifetime. But there is also some positive news in this research. It turns out that there is a particularly effective antidote to the ill effects of early stress, and it comes not from pharmaceutical companies or early-childhood educators but from parents. Parents and other caregivers who are able to form close, nurturing relationships with their children can foster resilience in them that protects them from many of the worst effects of a harsh early environment. This message can sound a bit warm and fuzzy, but it is rooted in cold, hard science. The effect of good parenting is not just emotional or psychological, the neuroscientists say; it is biochemical.

The researcher who has done the most to expand our understanding of the relationship between parenting and stress is a neuroscientist at McGill University named Michael Meaney. Like many in the field, Meaney does much of his research with rats, as rats and humans have similar brain architecture. At any given time, the Meaney lab houses hundreds of rats. They live in Plexiglas cages, and usually each cage holds a mother rat, called a dam, and her small brood of baby rats, called pups.

Scientists in rat labs are always picking up baby rats to examine them or weigh them, and one day about ten years ago, researchers in Meaney’s lab noticed a curious thing
: When they put the pups back in the cages after handling them, some dams would scurry over and spend a few minutes licking and grooming their pups. Others would just ignore them. When the researchers examined the rat pups, they discovered that this seemingly insignificant practice had a distinct physiological effect. When a lab assistant handled a rat pup, researchers found, it produced anxiety, a flood of stress hormones, in the pup. The dam’s licking and grooming counteracted that anxiety and calmed down that surge of hormones.

Meaney and his researchers were intrigued, and they wanted to learn more about how licking and grooming worked and what kind of effect it had on the pups. So they kept watching the rats, spending long days and nights with their faces pressed up against the Plexiglas, and after many weeks of careful observation, they made an additional discovery: different mother rats had different patterns of licking and grooming, even in the absence of their pups’ being handled. So Meaney’s team undertook a new experiment, with a new set of dams, to try to quantify these patterns. This time, they didn’t handle any of the pups. They just closely observed each cage, an hour at a time, eight sessions a day, for the first ten days of the pups’ lives. Researchers counted every instance of maternal licking and grooming.
And after ten days, they divided the dams into two categories: the ones that licked and groomed a lot, which they labeled high LG, and the ones that licked and groomed a little, which they labeled low LG.

The researchers wanted to know what the long-term effects of these variations in parenting behavior might be. So when the pups were twenty-two days old, they were weaned, separated from their mothers, and housed for the rest of their adolescence with same-sex siblings. When the pups were fully mature, about a hundred days old, Meaney’s team gave them a series of tests that compared the offspring of the high-licking-and-grooming dams with the rats that hadn’t received a lot of licking and grooming as pups.

The main evaluation they used was something called an open-field test, a common procedure in animal-behavior studies: A rat is placed in a large, round, open box for five minutes and allowed to explore at will. Nervous rats tend to stay close to the wall, circling around and around the perimeter; bolder rats dare to venture away from the wall and explore the whole field. In a second test, designed to measure fearfulness, hungry rats were placed in a new cage for ten minutes and offered food. Anxious rats, like jittery guests at a fancy dinner party, tend to take longer to work up the nerve to try any food, and they eat less than the calmer, more confident rats do.

On both tests, the difference between the two groups was striking. The rats who hadn’t been licked and groomed much as pups spent, on average, fewer than five seconds of their five minutes daring to explore the inner part of the open field; the rats who had been licked and groomed a lot as pups spent, on average, thirty-five seconds in the inner field—seven times as long. In the ten-minute food test, high-LG rats began eating, on average, after just four tentative minutes, and they ate for more than two minutes in total. The low-LG rats took, on average, more than nine minutes to start eating, and once they did, they ate for only a few seconds.

The researchers ran test after test, and on each one, the high-LG offspring excelled: They were better at mazes. They were more social. They were more curious. They were less aggressive. They had more self-control. They were healthier. They lived longer. Meaney and his researchers were astounded. What seemed like a tiny variation in early mothering style, so small that decades of researchers hadn’t noticed it, created huge behavioral differences in mature rats, months after the licking and grooming had taken place. And the effect wasn’t just behavioral; it was biological too. When Meaney’s researchers examined the brains of the adult rats, they found significant differences in the stress-response systems of the high-LG and low-LG rats, including big variations in the size and shape and complexity of the parts of the brain that regulated stress.

Meaney wondered if a dam’s licking-and-grooming frequency was just a proxy for some genetic trait that was passed on from mother to child. Maybe nervous dams produced temperamentally nervous pups, and those dams also coincidentally happened to be less inclined to lick and groom. To test that hypothesis, Meaney and his researchers did a number of cross-fostering experiments,
in which they removed pups at birth from a high-LG dam and put them in the litter of a low-LG dam, and vice versa, in all kinds of combinations. Whatever permutation they chose, though, however they performed the experiment, they found the same thing: what mattered was not the licking-and-grooming habits of the biological mother; it was the licking-and-grooming habits of the
rearing
mother. When a pup received the comforting experience of licking and grooming as an infant, it grew up to be braver and bolder and better adjusted than a pup who hadn’t, whether or not its biological mother was the one who had done the licking and grooming.

10. Attachment

Meaney and other neuroscientists have found intriguing evidence that something like the LG effect takes place in humans as well. In collaborations with geneticists over the past decade, Meaney and his researchers have been able to demonstrate that a dam’s licking and grooming doesn’t affect her pups just on the level of their hormones and brain chemicals. It goes much deeper than that,
all the way down to the control of gene expression. Licking and grooming a rat pup in its earliest days of life affects the way certain chemicals are affixed to certain sequences on the pup’s DNA, a process known as methylation. Using gene-sequencing technology, Meaney’s team was able to establish which part of a pup’s genome got “switched on” by licking and grooming, and it turned out to be the precise segment that controlled the way the rat’s hippocampus would process stress hormones in adulthood.

That discovery alone caused a sensation in the world of neuroscience. It showed that, in rats at least, subtle parental behaviors had predictable and long-lasting DNA-related effects that could actually be traced and observed. What made the discovery relevant beyond the rodent world was an experiment that Meaney’s team then went on to do using the brain tissue of human suicides
—some from suicides who had been maltreated and abused in childhood, and some from suicides who had not. The researchers sliced into the brain tissue and examined the sites on the DNA that are related to the stress response in the hippocampus—the human equivalent of the rat DNA sequence that was switched on by early parental behavior, profoundly affecting the rat’s future reactions. They discovered that the suicides who had been maltreated and abused in childhood had experienced methylation effects on that exact segment of their DNA, though the abuse had the opposite effect of licking and grooming: it had switched off the healthy stress-response function that licking and grooming had switched on in the rat pups.

The suicide study is definitely intriguing, but on its own, it does not amount to conclusive evidence about the effect of parenting on stress function in humans. But more solid evidence is beginning to emerge, thanks to some innovative studies that build on Meaney’s research. Clancy Blair, a researcher in psychology at NYU,
has been conducting a large-scale experiment in which he has followed almost from birth a group of more than twelve hundred infants. Every year or so, beginning when the infants were just seven months old, Blair measured the way their cortisol levels spiked in reaction to stressful situations—a simple way to evaluate how well a child is handling stress, kind of a bare-bones index of allostatic load. Blair found that environmental risks, like family turmoil and chaos and crowding, did have a big effect on children’s cortisol levels—but only when their mothers were inattentive or unresponsive. When mothers scored high on measures of responsiveness
, the impact of those environmental factors on their children seemed almost to disappear. High-quality mothering, in other words, can act as a powerful buffer against the damage that adversity inflicts on a child’s stress-response system, much as the dams’ licking and grooming seemed to protect their pups.

Gary Evans, the Cornell scientist
who tested the Simon-playing ability of the cohort of children in upstate New York he has been studying for almost two decades, conducted a similar experiment as Blair’s, though his subjects were in middle school. He collected three different kinds of data for each child: a cumulative-risk score that took into account everything from the ambient noise in a child’s home to the results of a questionnaire about family friction; an allostatic-load measure that incorporated blood pressure, the level of stress hormones in urine, and body mass index; and a rating of maternal responsiveness, which combined the child’s answers to a series of questions about his or her mother with a researcher’s observations of the mother and child playing Jenga together (another Hasbro game!). Evans found mostly what you’d expect: the higher the environmental-risk score, the higher the allostatic-load score—
unless
a child’s mother was particularly responsive to her child. If that was the case, the effect of all of those environmental stressors, from overcrowding to poverty to family turmoil, was almost entirely eliminated. If your mom was particularly sensitive to your emotional state during a game of Jenga, in other words, all the bad stuff you faced in life had little to no effect on your allostatic load.

When we consider the impact of parenting on children, we tend to think that the dramatic effects are going to appear at one end or the other of the parenting-quality spectrum. A child who is physically abused is going to fare far worse, we assume, than a child who is simply ignored or discouraged. And the child of a supermom who gets lots of extra tutoring and one-on-one support is going to do way better than an average well-loved child. But what Blair’s and Evans’s research suggests is that regular good parenting—being helpful and attentive during a game of Jenga—can make a profound difference for a child’s future prospects.

Some psychologists believe that the closest parallel to licking and grooming in humans can be found in a phenomenon called attachment. Attachment theory was developed in the 1950s and 1960s
by a British psychoanalyst named John Bowlby and a researcher from the University of Toronto named Mary Ainsworth. At the time, the field of child development was dominated by behaviorists, who believed that children developed in a mechanical way, adapting their behavior according to the positive and negative reinforcement they experienced. Children’s emotional lives were not very deep, behaviorists believed; an infant’s apparent yearning for his mother was nothing more than an indication of his biological needs for nourishment and physical comfort. The dominant advice to parents in the 1950s, based on behavioral theory, was to avoid “spoiling” infants by picking them up or otherwise comforting them when they cried.

In a series of studies in the 1960s and early 1970s, Ainsworth showed that the effect of early nurturance was exactly the opposite of what the behaviorists expected. Babies whose parents responded readily and fully to their cries in the first months of life were, at one year, more independent and intrepid than babies whose parents had ignored their cries. In preschool, the pattern continued—the children whose parents had responded most sensitively to their emotional needs as infants were the most self-reliant. Warm, sensitive parental care, Ainsworth and Bowlby contended, created a “secure base” from which a child could explore the world.

Although psychologists in the 1960s had at their disposal many tests to evaluate the cognitive abilities of infants and children, they had no reliable way to measure a child’s emotional capacities. So Ainsworth invented a method to do just that, an unusual procedure called the Strange Situation. At Johns Hopkins University, in Baltimore, where Ainsworth was a professor, a mother would bring her twelve-month-old child into a lab set up as a playroom. After playing with her infant for a while, the mother left the room, sometimes leaving the child with a stranger, sometimes leaving him or her alone. After a brief interval, she would return. Ainsworth and her researchers observed the whole procedure through one-way mirrors, and then categorized the children’s reactions.

Most children greeted the returning mother happily, running to her and reconnecting with her, sometimes tearfully, sometimes with joy. These children Ainsworth labeled securely attached, and in subsequent experiments over the past few decades, psychologists have come to believe that they make up about 60 percent of American children. Children who did not have a warm reunion—pretending to ignore the mother when she returned; lashing out at her; falling to the floor in a heap—were labeled anxiously attached. Ainsworth found that a child’s reaction in the Strange Situation was directly related to his parents’ degree of responsiveness in that first year of life. Parents who were attuned to their child’s mood and responsive to his cues produced securely attached children; parenting that was detached or conflicted or hostile produced anxiously attached children. And early attachment, Ainsworth said, created psychological effects that could last a lifetime.