Life on a caribbean island isn’t all fun and games. By measuring stress hormones in Dominican children, anthropologist Mark Flinn is showing where the tension lies.
Loping through the village of Bwa Mawego, on the Caribbean island of Dominica, Mark Flinn looks and acts like a slimmer, bespectacled Al Gore stumping on the campaign trail. He stops at each house to chat. He shakes hands, touches shoulders. He asks parents about their children in lilting Creole and talks of his own three young boys back home. At the University of Missouri, where Flinn teaches anthropology, he is an admittedly aloof and distant colleague. But here in Bwa Mawego, everyone knows everything about everybody— "If you talk about someone and you don't see them soon," one villager says, "they are either in jail or in the cemetery"— and that suits Flinn just fine. In fact, his research depends on it. As Flinn makes his way up the crest of a ravine on a winding dirt road, he runs into two boys, aged 10 and 7, on their way to school. The boys have on the requisite brown shorts and pale yellow shirts and carry book bags. "Have time to spit?" Flinn asks
Flinn gives each boy a stick of Wrigley’s spearmint gum, and they chew and spit into plastic cups. Next, an elderly matriarch named Evelyn comes up the road and lends a hand. Moving like a veteran lab assistant, she takes a plastic pipette, deftly sucks up five milliliters of saliva from one of the boys’ cups, and transfers the saliva to a labeled tube. Finally, Flinn turns to the boys and asks them how things are at home. “When did you get up? Did anybody fall this morning? Did you sleep at your grandmother’s or at home?”
Two Schoolboys stop to give Mark Flinn saliva samples for his stress research. The gum Flinn gives them is God’s gift to endocrinologists, since it doesn’t react with stress hormones.
The whole sequence, described in that way, sounds faintly absurd. Yet every action here has a reasonable purpose, and Flinn’s lines are hardly non sequiturs. He is studying the relationship between stress and health in children, and two of the best ways to gauge stress are by asking personal questions and by measuring a hormone called cortisol, found in saliva. Since 1988, Flinn has collected more than 25,000 saliva samples from 287 children in this village—an average of 96 samples per child. He has tracked the children’s growth and measured their immunoglobulin levels to see if their immune systems are healthy.
He has checked their health records and sent out an assistant to see who’s sick. Perhaps most important, he has watched, listened, and asked questions. The result is a year-by-year, day-by-day, and sometimes even hour-by-hour glimpse of these children’s lives. It’s also a compelling rebuttal to one of the most widely publicized new theories in developmental psychology.
According to that theory, propounded by psychologist Judith Harris in her controversial 1998 book The Nurture Assumption, parents have relatively little power to shape a child’s character. Studies of identical twins raised apart since birth have proved “beyond a shadow of a doubt that heredity is responsible for a sizable portion of the variations in people’s personalities,” Harris writes. At the same time, she points to a number of studies that seemed to suggest that the rest of a child’s personality is shaped more by peers than by parents. How else—to take one example—could the children of non-English-speaking immigrants speak perfect English?
After generations of child-centered parenting books, Harris’s argument immediately captured the media spotlight, perhaps mostly because it lets parents off the hook. If The Nurture Assumption is right, parents can all relax, put their kids in day care, and stop worrying that a little scolding will damage them for life. As an article in The New Yorker put it: “In some key sense, parents don’t much matter.”
Flinn’s work makes an altogether different point—one as unfashionable as it is reasonable. His thousands of data points can be grouped into any number of constellations, but one pattern shines through all the others: Families matter more than anything else in a child’s life. When a family has problems, it sends stress hormones coursing through a child’s system. When family members get along, or have numerous relatives to call on, they can shelter a child from the worst social upheavals in the outside world. Emotionally and physiologically, family life is ground zero for a child’s health.
The payoff for Flinn’s 13-year study is a startlingly intimate view of childhood and its discontents
Bwa Mawego is the perfect setting for such research. (For the sake of privacy, the names of the village and all villagers have been changed.) Life is lived in the open here, making it far easier to meet people and follow them around, and many incidental sources of stress are naturally filtered out. There is no traffic, no rat race, no threat of war. The forest is fragrant with bay leaf bushes, the winding paths littered with ripe mangoes, the houses clustered in picturesque hamlets overlooking the sea. Of course, poverty, poor roads, and exposure to the elements take their own toll, but local people—some 700 of them, all of mixed African, Carib, and European descent—are unlikely to blame their stress on their surroundings.
Take Kristen, a 4-year-old in town. Every morning she wakes up to a billion-dollar view: Her house is built on stilts, on a volcanic cliff overlooking the Atlantic. In the front yard, clean laundry hangs on the trees that dot the hard-packed mud, chickens run about, and a soft Caribbean breeze wafts the smell of roasting coffee beans across the porch. With her large brown eyes, sweet smile, and quiet manner, Kristen is a child anyone would want to hug, and lots of people do—her mother, grandparents, and a multitude of relatives all live within walking distance.
Yet Kristen’s life has its share of stress. Before she was born, her mother, Julianne, was single and going to high school in the city. When Julianne became pregnant, she had to move back home and hasn’t worked since. Although Robbie, a nice guy and an old friend of Julianne’s, has since become a kind of stepfather to Kristen, Julianne still worries about the opportunities she missed by not getting an education. In Bwa Mawego, as in most places, life can be tough for a single mother. And today Kristen has a cold.
Children at home tend to have higher cortisol levels than children at school, one british study has shown. It seems that Life at home is far more unpredictable, and so more stressful.
Flinn sees no coincidence there. “In the village, illness among children increases more than twofold following significant stress,” he says. “About 30 percent of the children in the village have the current cold, even though most of them have been exposed to the pathogen. So why are only certain ones sick? In the West we think it is mostly contact—send your child to preschool and expect them to get sick. But I am convinced that resistance is more important than contact frequency.”
The reason is as complex biologically as it is emotionally. When a person is in trouble, Flinn explains, the brain automatically sends signals to the sympathetic nervous system, initiating a “fight or flight” response. First adrenaline and then cortisol are secreted by the adrenal glands, revving up the body and then sustaining the energy flow to different systems. The lungs pump faster and the heart starts to race; blood pressure rises, charging up the muscles and sharpening the mind; the stomach gets jumpy and the rush of endorphins numbs the body. At the same time, the appetite, libido, and immune system shut down, and the energy they would normally consume is diverted to muscles that will help the body fight the immediate threat.
This is all well and good—unless the perceived threat persists. In that case, adrenaline washes out of the body quickly, but cortisol may linger for days, weeks, or even years, keeping the immune system and other important functions depressed. Children are especially vulnerable to stress. Their bodies are “nothing other than a long-term building project,” says Robert Sapolsky, a stress researcher at Stanford University. Yet chronic stress is “constantly telling them, ‘Don’t fix stuff now, do it tomorrow, do it tomorrow.’” In the long term, too much cortisol can slow down a child’s growth, brain development, and sexual maturation. In the short term, it can make a child prone to upper-respiratory infections and diarrhea, diseases that are often fatal at that age.
Stress can make you sick.
Thanks to cortisol, measuring stress is as easy as a lab test or two. But only patient, detailed, long-term work like Flinn’s can untangle its myriad causes. Hormone levels differ from child to child, Flinn says, and they fluctuate naturally over the course of a day. “The old dogma was that if you got a sample once a day, collected between 8 and 10 a.m., that was enough. But I’ve found that controlling for time of day is not enough. If you have a tough kid who is habituated to the mundane, giving a saliva sample in a lab would be a bore. You need to know what happened to this kid the day before: Is he burned out? What are his reserves? What’s the context?”
The National Institute of Mental Health offers more about the effects of stress on developing brains: www.nimh.nih.gov/publicat/develop.cfm
Some studies suggest that stress can make children develop subtle asymmetries in their bodies. To check for such problems, Mark Flinn and his graduate student David Leone set up in front of the local school and use calipers to measure students. After the measuring, each child gets a little money to bring home and a lollipop from Dave, the “Poppie Man.” Data gathered on 238 children over the past four field seasons have shown that children who live with a stepfather—a situation often rife with stress—weigh less than others but are surprisingly more symmetrical. There seems to be no relationship, so far, between stress and growth asymmetry in these children.
Taking repeated measurements, as Flinn does, is expensive, complicated, and time-consuming. But the payoff is a startlingly intimate view of childhood and its discontents. One summer, for instance, Flinn took samples from a group of cousins, aged 3 to 8, who were playing house. Valerie and Kathy decided to be the parents, and they made Jane the child—a role of lowly status. Jane wasn’t happy being the child. Worse, she felt betrayed: Valerie was her best friend. Why had she sided with Kathy? So Jane organized the other children into a game of jump rope, ruining Valerie and Kathy’s plans.
A ruckus ensued. Kathy, still playing parent, told Jane she was being disobedient and threatened to beat her; Jane and her jump-rope partner swung the rope and hit Kathy in the face by mistake. Soon the children were yelling and their mothers were running over and accusations were flying. Kathy even threw a rock in Jane’s direction as they parted.
If children’s personalities are largely shaped by their peers, this should have been a traumatic event. Harris cites an informal study by sociologist Anne-Marie Ambert, of York University in Ontario, in which 37 percent of the students in a class blamed their most depressing experience on peers, while only 9 percent blamed it on parents. As evidence of peer influence, she also notes that siblings grow up to be very different adults; that adopted children are more like their biological parents than their adopted parents in terms of such traits as criminality; and that adolescents from poor neighborhoods are more likely to be delinquents than adolescents from middle-class neighborhoods, whereas being from a broken home has no effect on delinquency. Troubles with peers, Harris concludes, have a much deeper effect on children than do troubles at home.
Family life may weigh on children sometimes. But just as often, it lifts them out of the other tensions and anxieties in their lives.
Flinn’s work shows just the opposite. Soon after Jane, Kathy, and Valerie’s fight, he collected saliva from each of the participants. None of them had high levels of cortisol. “None,” he repeats. “And this is typical of mild peer conflicts.” Yet several weeks later, when Jane returned home late from a shopping errand, her saliva told a different story. This time it was her real mother, rather than Kathy, who did the scolding, and though Jane quietly went about her schoolwork afterward, her cortisol rose 60 percent above normal.
Flinn has seen the same pattern time and again. He has taken cortisol measurements from children engaged in 30 different types of activities—from “family fight” to“fight with peer”—and they consistently show that families cause more stress than peers do. Only major fights with friends elevate cortisol levels as much as family troubles do.
Flinn’s work gets at a fundamental truth about children, one that distinguishes them from the offspring of almost any other species. Most mammals are weaned within days or weeks of their birth. But human infants have to nurse for months, and they need a year just to learn how to walk. Their parents do more than usher them into the world; they feed, clothe, shelter, and protect them for a good portion of their lives. “Humans have the luxury of extended families who can care for these mental larvae,” Flinn says. “And because of that protection, children can afford to have a brain that is in the process of growing.” At the same time, he adds, children are designed to be exquisitely attuned to their caregivers: “There is nothing more important to a child than figuring out what makes those close to them happy, and what makes them sad.”
This week, the Cabot family is a living experiment in the physiology of stress. Their middle child, 6-year-old Harrison, was born with one leg shorter than the other—a handicap so severe that he can’t walk to school.
Now, after working and saving for many years, Harrison’s father, John, is taking him to Shriner’s Hospital in Tampa Bay, Florida, for an operation. Afterward, Harrison must undergo four months of intense physical therapy before he and John can return home.
Meanwhile, Harrison’s mother, Joyce, will have to care for his three brothers, Kirk, Paul, and Donald, as well as the new baby Louise. To see how the family is coping, Mark Flinn measures the boys’ cortisol several times a day before and after the departure and talks to them about how they feel. Although the brothers act as if Harrison’s trip is no big deal, their cortisol levels (adjusted according to their natural daily fluctuations) tell a different story.
The mean cortisol level for the village is zero. Anything above that indicates unusual stress. Over the nine years that he has been following the Cabots, Flinn has found them to be relatively stable, loving, and relaxed—“just a real happy family”—with a mean cortisol level of -0.29.
Yet in the week before Harrison’s departure their mean level rose to 1.32, and on the morning after Harrison left, 4-year-old Donald’s cortisol rose nearly eight standard deviations above the mean. “That’s pretty darn dramatic,” Flinn says. “You might see that only once every 10,000 cases. Obviously, their brains are kind of working to see how they are going to deal with the new situation.” —M.F.S.
Contrary to the studies that Harris cites, Flinn has found that children who live with both biological parents clearly do best. They have lower average cortisol levels, weigh more, and grow more steadily than those living with stepparents or single parents with no support from kin. Flinn has also found that boys from households without fathers (though not girls) have cortisol levels that are too low in infancy and grow slower than boys with fathers at home. Once again, parents do matter; their impact is sometimes just too deep to notice.
We expect our children to be happy-go-lucky and resilient, but Flinn has found that they aren’t as adaptable as we think. In Bwa Mawego, for instance, Aretha and Arnie Belle have five children, three of them still at home. But Arnie fools around, and so Aretha left him in the fall of 1990 and stayed with her sister in Martinique. During Aretha’s absence, her children’s cortisol levels shot up and did not come down until she came home a year later. It seems the children never adapted to living in a single-parent home.
Children with such chronically high cortisol levels can suffer permanent damage. In Romania, for instance, orphans raised under the dictatorship of Nicolae Ceaus,escu were often so completely neglected—aside from perfunctory feedings and diaper changings—that they became withdrawn and temperamental, prone to rocking in place and staring blankly at visitors. Psychologist Elinor Ames, of Simon Fraser University in British Columbia, studied two groups of orphans. Those in the first group were adopted by American families by the age of 4 months; the second group spent eight months or more in an orphanage. Three years after adoption, the children in the first group had caught up to their peers in terms of size and maturity. But many of those who spent the longest time in the orphanage still suffered from depression and withdrawal.
One sunny morning in January, a chubby little girl named Maryann, from the apartment downstairs, toddles up to Flinn’s apartment and crawls onto his sofa. Maryann has on a bright pink dress and her hair is pleated into cornrows topped with plastic bows, but she isn’t feeling quite so sunny. She has been running a fever and coughing all night, her grandmother explains, as several adults jump up with a tissue to wipe the girl’s runny nose.
“She’s had this cold for a few days,” Flinn guesses. But unlike so many illnesses he has seen these past 13 years, this one probably wasn’t exacerbated by stress. Day and night, Maryann is surrounded by loving family members, he says. “It seems like she’s related to everyone in town.” Such extended families, in turn, allow for much more flexibility in child care. In Bwa Mawego, 36 percent of households with children changed composition at least once between 1990 and 1995—a statistic not unusual for the Caribbean; over the same period about a third of the children lived in more than one household. Fathers often spend the late summer and fall working on farms in Canada; mothers work away from the village at resorts; children go to the city to live with their grandparents. But even when children change houses, many of them are still with relatives who know all about them—and they are demonstrably healthier for it. Children with many kin connections, Flinn has found, are both taller and heavier for their age than children with few relatives.
There may be an underlying lesson here for Dominica’s more industrialized neighbors: Although nuclear families are the bedrock of Western societies, they’re also prone to rifts and tremors—and children tend to fall through the cracks. In that sense, Harris may be partly right, and her differences with Flinn are partly a function of the different cultures they study. In the United States, families are an infant’s first peer group, but children soon grow out of them. Without cousins, grandparents, and other relatives nearby to fill out their lives, they have to find their role models on the playground. In Bwa Mawego, by contrast, families tend to be fluid, amorphous entities, with kin networks extensive enough to guide and support children well past adolescence.
Maryann probably caught her cold from her father, a taxi driver. But with everyone in her family keeping close watch, Flinn knows that she will be fine soon. Money may be scarce here on Bwa Mawego, and health care may not be up to Western standards. But when it comes to avoiding stress, a happy family is a child’s greatest asset—greater even than nice friends and billion-dollar views, and a house by the sea in a small slice of paradise.