by Susan Cain
I decided to track down Professor Kagan to ask him these questions in person. I felt drawn to him not only because his research findings were so compelling, but also because of what he represents in the great nature-nurture debate. He’d launched his career in 1954 staunchly on the side of nurture, a view in step with the scientific establishment of the day. Back then, the idea of inborn temperament was political dynamite, evoking the specter of Nazi eugenics and white supremacism. By contrast, the notion of children as blank slates for whom anything was possible appealed to a nation built on democracy.
But Kagan had changed his mind along the way. “I have been dragged, kicking and screaming, by my data,” he says now, “to acknowledge that temperament is more powerful than I thought and wish to believe.” The publication of his early findings on high-reactive children in Science magazine in 1988 helped to legitimize the idea of inborn temperament, partly because his “nurturist” reputation was so strong.
If anyone could help me untangle the nature-nurture question, I hoped, it was Jerry Kagan.
Kagan ushers me inside his office in Harvard’s William James Hall, surveying me unblinkingly as I sit down: not unkind, but definitely discerning. I had imagined him as a gentle, white-lab-coated scientist in a cartoon, pouring chemicals from one test tube to another until—poof! Now, Susan, you know exactly who you are. But this isn’t the mild-mannered old professor I’d imagined. Ironically for a scientist whose books are infused with humanism and who describes himself as having been an anxious, easily frightened boy, I find him downright intimidating. I kick off our interview by asking a background question whose premise he disagrees with. “No, no, no!” he thunders, as if I weren’t sitting just across from him.
The high-reactive side of my personality kicks into full gear. I’m always soft-spoken, but now I have to force my voice to come out louder than a whisper (on the tape recording of our conversation, Kagan’s voice sounds booming and declamatory, mine much quieter). I’m aware that I’m holding my torso tensely, one of the telltale signs of the high-reactive. It feels strange to know that Kagan must be observing this too—he says as much, nodding at me as he notes that many high-reactives become writers or pick other intellectual vocations where “you’re in charge: you close the door, pull down the shades and do your work. You’re protected from encountering unexpected things.” (Those from less educated backgrounds tend to become file clerks and truck drivers, he says, for the same reasons.)
I mention a little girl I know who is “slow to warm up.” She studies new people rather than greeting them; her family goes to the beach every weekend, but it takes her ages to dip a toe into the surf. A classic high-reactive, I remark.
“No!” Kagan exclaims. “Every behavior has more than one cause. Don’t ever forget that! For every child who’s slow to warm up, yes, there will be statistically more high-reactives, but you can be slow to warm up because of how you spent the first three and a half years of your life! When writers and journalists talk, they want to see a one-to-one relationship—one behavior, one cause. But it’s really important that you see, for behaviors like slow-to-warm-up, shyness, impulsivity, there are many routes to that.”
He reels off examples of environmental factors that could produce an introverted personality independently of, or in concert with, a reactive nervous system: A child might enjoy having new ideas about the world, say, so she spends a lot of time inside her head. Or health problems might direct a child inward, to what’s going on inside his body.
My fear of public speaking might be equally complex. Do I dread it because I’m a high-reactive introvert? Maybe not. Some high-reactives love public speaking and performing, and plenty of extroverts have stage fright; public speaking is the number-one fear in America, far more common than the fear of death. Public speaking phobia has many causes, including early childhood setbacks, that have to do with our unique personal histories, not inborn temperament.
In fact, public speaking anxiety may be primal and quintessentially human, not limited to those of us born with a high-reactive nervous system. One theory, based on the writings of the sociobiologist E. O. Wilson, holds that when our ancestors lived on the savannah, being watched intently meant only one thing: a wild animal was stalking us. And when we think we’re about to be eaten, do we stand tall and hold forth confidently? No. We run. In other words, hundreds of thousands of years of evolution urge us to get the hell off the stage, where we can mistake the gaze of the spectators for the glint in a predator’s eye. Yet the audience expects not only that we’ll stay put, but that we’ll act relaxed and assured. This conflict between biology and protocol is one reason that speechmaking can be so fraught. It’s also why exhortations to imagine the audience in the nude don’t help nervous speakers; naked lions are just as dangerous as elegantly dressed ones.
But even though all human beings may be prone to mistaking audience members for predators, each of us has a different threshold for triggering the fight-or-flight response. How threateningly must the eyes of the audience members narrow before you feel they’re about to pounce? Does it happen before you’ve even stepped onstage, or does it take a few really good hecklers to trigger that adrenaline rush? You can see how a highly sensitive amygdala would make you more susceptible to frowns and bored sighs and people who check their BlackBerrys while you’re in mid-sentence. And indeed, studies do show that introverts are significantly more likely than extroverts to fear public speaking.
Kagan tells me about the time he watched a fellow scientist give a wonderful talk at a conference. Afterward, the speaker asked if they could have lunch. Kagan agreed, and the scientist proceeded to tell him that he gives lectures every month and, despite his capable stage persona, is terrified each time. Reading Kagan’s work had had a big impact on him, however.
“You changed my life,” he told Kagan. “All this time I’ve been blaming my mother, but now I think I’m a high-reactive.”
So am I introverted because I inherited my parents’ high reactivity, copied their behaviors, or both? Remember that the heritability statistics derived from twin studies show that introversion-extroversion is only 40 to 50 percent heritable. This means that, in a group of people, on average half of the variability in introversion-extroversion is caused by genetic factors. To make things even more complex, there are probably many genes at work, and Kagan’s framework of high reactivity is likely one of many physiological routes to introversion. Also, averages are tricky. A heritability rate of 50 percent doesn’t necessarily mean that my introversion is 50 percent inherited from my parents, or that half of the difference in extroversion between my best friend and me is genetic. One hundred percent of my introversion might come from genes, or none at all—or more likely some unfathomable combination of genes and experience. To ask whether it’s nature or nurture, says Kagan, is like asking whether a blizzard is caused by temperature or humidity. It’s the intricate interaction between the two that makes us who we are.
So perhaps I’ve been asking the wrong question. Maybe the mystery of what percent of personality is nature and what percent nurture is less important than the question of how your inborn temperament interacts with the environment and with your own free will. To what degree is temperament destiny?
On the one hand, according to the theory of gene-environment interaction, people who inherit certain traits tend to seek out life experiences that reinforce those characteristics. The most low-reactive kids, for example, court danger from the time they’re toddlers, so that by the time they grow up they don’t bat an eye at grown-up-sized risks. They “climb a few fences, become desensitized, and climb up on the roof,” the late psychologist David Lykken once explained in an Atlantic article. “They’ll have all sorts of experiences that other kids won’t. Chuck Yeager (the first pilot to break the sound barrier) could step down from the belly of the bomber into the rocketship and push the button not because he was born with that difference between him and me, but because for the previous thirty years his te
mperament impelled him to work his way up from climbing trees through increasing degrees of danger and excitement.”
Conversely, high-reactive children may be more likely to develop into artists and writers and scientists and thinkers because their aversion to novelty causes them to spend time inside the familiar—and intellectually fertile—environment of their own heads. “The university is filled with introverts,” observes the psychologist Jerry Miller, director of the Center for the Child and the Family at the University of Michigan. “The stereotype of the university professor is accurate for so many people on campus. They like to read; for them there’s nothing more exciting than ideas. And some of this has to do with how they spent their time when they were growing up. If you spend a lot of time charging around, then you have less time for reading and learning. There’s only so much time in your life.”
On the other hand, there is also a wide range of possible outcomes for each temperament. Low-reactive, extroverted children, if raised by attentive families in safe environments, can grow up to be energetic achievers with big personalities—the Richard Bransons and Oprahs of this world. But give those same children negligent caregivers or a bad neighborhood, say some psychologists, and they can turn into bullies, juvenile delinquents, or criminals. Lykken has controversially called psychopaths and heroes “twigs on the same genetic branch.”
Consider the mechanism by which kids acquire their sense of right and wrong. Many psychologists believe that children develop a conscience when they do something inappropriate and are rebuked by their caregivers. Disapproval makes them feel anxious, and since anxiety is unpleasant, they learn to steer clear of antisocial behavior. This is known as internalizing their parents’ standards of conduct, and its core is anxiety.
But what if some kids are less prone to anxiety than others, as is true of extremely low-reactive kids? Often the best way to teach these children values is to give them positive role models and to channel their fearlessness into productive activities. A low-reactive child on an ice-hockey team enjoys his peers’ esteem when he charges at his opponents with a lowered shoulder, which is a “legal” move. But if he goes too far, raises his elbow, and gives another guy a concussion, he lands in the penalty box. Over time he learns to use his appetite for risk and assertiveness wisely.
Now imagine this same child growing up in a dangerous neighborhood with few organized sports or other constructive channels for his boldness. You can see how he might fall into delinquency. It may be that some disadvantaged kids who get into trouble suffer not solely from poverty or neglect, say those who hold this view, but also from the tragedy of a bold and exuberant temperament deprived of healthy outlets.
The destinies of the most high-reactive kids are also influenced by the world around them—perhaps even more so than for the average child, according to a groundbreaking new theory dubbed “the orchid hypothesis” by David Dobbs in a wonderful article in The Atlantic. This theory holds that many children are like dandelions, able to thrive in just about any environment. But others, including the high-reactive types that Kagan studied, are more like orchids: they wilt easily, but under the right conditions can grow strong and magnificent.
According to Jay Belsky, a leading proponent of this view and a psychology professor and child care expert at the University of London, the reactivity of these kids’ nervous systems makes them quickly overwhelmed by childhood adversity, but also able to benefit from a nurturing environment more than other children do. In other words, orchid children are more strongly affected by all experience, both positive and negative.
Scientists have known for a while that high-reactive temperaments come with risk factors. These kids are especially vulnerable to challenges like marital tension, a parent’s death, or abuse. They’re more likely than their peers to react to these events with depression, anxiety, and shyness. Indeed, about a quarter of Kagan’s high-reactive kids suffer from some degree of the condition known as “social anxiety disorder,” a chronic and disabling form of shyness.
What scientists haven’t realized until recently is that these risk factors have an upside. In other words, the sensitivities and the strengths are a package deal. High-reactive kids who enjoy good parenting, child care, and a stable home environment tend to have fewer emotional problems and more social skills than their lower-reactive peers, studies show. Often they’re exceedingly empathic, caring, and cooperative. They work well with others. They are kind, conscientious, and easily disturbed by cruelty, injustice, and irresponsibility. They’re successful at the things that matter to them. They don’t necessarily turn into class presidents or stars of the school play, Belsky told me, though this can happen, too: “For some it’s becoming the leader of their class. For others it takes the form of doing well academically or being well-liked.”
The upsides of the high-reactive temperament have been documented in exciting research that scientists are only now beginning to pull together. One of the most interesting findings, also reported in Dobbs’s Atlantic article, comes from the world of rhesus monkeys, a species that shares about 95 percent of its DNA with humans and has elaborate social structures that resemble our own.
In these monkeys as well as in humans, a gene known as the serotonin-transporter (SERT) gene, or 5-HTTLPR, helps to regulate the processing of serotonin, a neurotransmitter that affects mood. A particular variation, or allele, of this gene, sometimes referred to as the “short” allele, is thought to be associated with high reactivity and introversion, as well as a heightened risk of depression in humans who have had difficult lives. When baby monkeys with a similar allele were subjected to stress—in one experiment they were taken from their mothers and raised as orphans—they processed serotonin less efficiently (a risk factor for depression and anxiety) than monkeys with the long allele who endured similar privations. But young monkeys with the same risky genetic profile who were raised by nurturing mothers did as well as or better than their long-allele brethren—even those raised in similarly secure environments—at key social tasks, like finding playmates, building alliances, and handling conflicts. They often became leaders of their troops. They also processed serotonin more efficiently.
Stephen Suomi, the scientist who conducted these studies, has speculated that these high-reactive monkeys owed their success to the enormous amounts of time they spent watching rather than participating in the group, absorbing on a deep level the laws of social dynamics. (This is a hypothesis that might ring true to parents whose high-reactive children hover observantly on the edges of their peer group, sometimes for weeks or months, before edging successfully inside.)
Studies in humans have found that adolescent girls with the short allele of the SERT gene are 20 percent more likely to be depressed than long-allele girls when exposed to stressful family environments, but 25 percent less likely to be depressed when raised in stable homes. Similarly, short allele adults have been shown to have more anxiety in the evening than others when they’ve had stressful days, but less anxiety on calm days. High-reactive four-year-olds give more pro-social responses than other children when presented with moral dilemmas—but this difference remains at age five only if their mothers used gentle, not harsh, discipline. High-reactive children raised in supportive environments are even more resistant than other kids to the common cold and other respiratory illnesses, but get sick more easily if they’re raised in stressful conditions. The short allele of the SERT gene is also associated with higher performance on a wide range of cognitive tasks.
These findings are so dramatic that it’s remarkable no one arrived at them until recently. Remarkable, but perhaps not surprising. Psychologists are trained to heal, so their research naturally focuses on problems and pathology. “It is almost as if, metaphorically speaking, sailors are so busy—and wisely—looking under the water line for extensions of icebergs that could sink their ship,” writes Belsky, “that they fail to appreciate that by climbing on top of the iceberg it might prove possible to chart a clear passage thr
ough the ice-laden sea.”
The parents of high-reactive children are exceedingly lucky, Belsky told me. “The time and effort they invest will actually make a difference. Instead of seeing these kids as vulnerable to adversity, parents should see them as malleable—for worse, but also for better.” He describes eloquently a high-reactive child’s ideal parent: someone who “can read your cues and respect your individuality; is warm and firm in placing demands on you without being harsh or hostile; promotes curiosity, academic achievement, delayed gratification, and self-control; and is not harsh, neglectful, or inconsistent.” This advice is terrific for all parents, of course, but it’s crucial for raising a high-reactive child. (If you think your child might be high-reactive, you’re probably already asking yourself what else you can do to cultivate your son or daughter. Chapter 11 has some answers.)
But even orchid children can withstand some adversity, Belsky says. Take divorce. In general, it will disrupt orchid kids more than others: “If the parents squabble a lot, and put their kid in the middle, then watch out—this is the kid who will succumb.” But if the divorcing parents get along, if they provide their child with the other psychological nutrients he needs, then even an orchid child can do just fine.
Most people would appreciate the flexibility of this message, I think; few of us had problem-free childhoods.