For Kagan this faith began to weaken in the early seventies, when he spent a year in Guatemala observing infants in a remote mountain village. The village children were of particular interest because of an unusually deprived first year of life that sprang from the Indians’ tradition. Local custom had the mothers isolating their children inside cramped dark huts for the first year, never allowing them outside, never playing with them, and almost never speaking to them. As a result, the children at the ages of one and two were observed to be unusually passive, quiet, and unresponsive. To Kagan, some appeared borderline retarded.
Setting to work, Kagan and his colleagues set up a controlled study in which the village kids were measured on a number of cognitive functions. Those results were then compared with a Guatemalan group raised in a more normal fashion near a city and with a group of middle-class American children. The three groups might roughly be termed understimulated, normally stimulated, and overstimulated.
The results showed that while the deprived village children measured lower in all tests in the first years, they tended to catch up as they grew older and their rearing setting became more similar to those of childhoods everywhere—outdoor play, interaction with parents, with other children, and so on. By eleven and twelve the Guatemalan children could be considered normally developed. This transformation was heartening to environmentalists like Kagan and to socially concerned individuals who placed hopes in intervention programs like Head Start which help underperforming children catch up with their age groups. Good behaviorist soldier that he was, Kagan wrote in an early paper on this study, “The data prove the potency of the environment.” Without hesitating he credited the good environment with remedying the effects of the bad.
But the data, he came to realize, could be seen in two ways. With the Guatemalan village children, there had been no intervention, no remedial program; they had merely been delivered from the negative environment of their first year, the dark hut. Something else seemed to be causing their improvement, and future evidence indicated it was their own normal development, in all likelihood their own genetic makeup triumphing over an adverse environment. Rather than the normal “outdoor” environment curing the negative effects of the grim first year, it may have merely allowed the child’s personality to unfold as its genome, or as “nature,” intended. While Kagan did not express it in those terms, he would later say something very close to the same thing, but in a turned-around way: “My belief in the power of early experience [in children’s development] was shaken.”
Shaken, perhaps, but Kagan, like the rest of the psychological profession, continued to believe in the environment as the most important molder of personality. His epiphany came fifteen years later, when he was working in Boston on a longitudinal study of infants, observing them from seven to twenty-nine months, with the aim of assessing the effectiveness of day care. The group was made up of fifty-three Chinese-American infants and sixty-three Caucasian children. Part of the entire group had from the age of four months attended an experimental day-care center set up for the study, part had attended other day-care centers, and part had been raised at home.
In the course of the experiment, Kagan noticed something unanticipated. The Chinese children, little more than babies, whether attending day care or raised at home, were consistently more fearful and inhibited than the Caucasians. The differences were obvious. The Chinese children stayed close to their mothers and were quiet and generally apprehensive, while the Caucasians were talkative, active, and “prone to laughter.” These characteristics were confirmed by the mothers as typical of their children’s behavior at home as well. In addition, the researchers discovered that the Chinese tots had less variable heart rates than the Caucasians. Kagan could not avoid the clear evidence of an innate difference between the two groups of infants.
It is ironic that this scientist’s conversion to a biological-genetic point of view came along the lines of racial differences. Kagan was a political liberal who only three years earlier had been one of the most vociferous critics of Arthur Jensen’s theories on the heritability of I.Q., theories that he and most everyone else denounced as racist. Now he was publishing his observations of fundamental personality differences between racial groups. When we conversed in his Harvard office many years later, I asked Kagan if there had been an uproar similar to the one Jensen provoked.
He smiled. “We got no flak on the Chinese paper. All the reports of the book were about our day-care findings. Everyone ignored the fact that the Chinese children were different. I think it was because they were Asians, and Asians do well. If they had been black, we probably would have gotten flak.”
Asked if it was dismaying for him, an unwavering liberal, to observe inherent racial differences, Kagan snapped, “Nature doesn’t care what we want.” More reflectively, he added, “I wasn’t so much dismayed at my observations of the Chinese kids.… I was a little bit saddened to see the power of biology.”
His major conclusion was stated in a 1988 paper in Science: “We suggest, albeit speculatively, that most of the children we call inhibited belong to a qualitatively distinct category of infants who were born with a lower threshold for limbic-hypothalamic arousal to unexpected changes in the environment or novel events that cannot be assimilated easily.”
It is revealing that in a sentence that is basically saying “kids are born that way,” Kagan, who had thrown himself into a self-education program of brain biochemistry, manages to avoid the word genes yet does find a way to work in the word environment. In the article’s abstract he speaks of “the inherited variation in the threshold of arousal in selected limbic sites.” But still, not a gene in sight. He appears to be worried about the limbic-hypothalamic arousal of the environmentalists down the hall. Or the word gene may have been forbidden at Harvard at the time. A more likely explanation is that Kagan, as a new convert to the biology of behavior, could not switch so quickly to the terminology of the infidels.
In his study of brain chemistry, Kagan grew convinced of the major effect on the traits he was examining of the liquid mix of neurotransmitters, hormones, and opioids that surround the operating parts of the brain. This mixture, which he refers to as “the chemical broth,” is made up of 150 chemicals in combinations that vary within individuals. While he believed there might be hundreds of possible combinations, his research had found two: ones that raise the threshold of excitability leading to inhibited children and ones that lower it to produce uninhibited children. This was a remarkable area of investigation for a behavioral psychologist who for years had believed in the sovereignty of the environment and had fought off any notion of biological or genetic influence on behavior. Kagan was, so to speak, in the soup.
Today, Kagan is hard on himself about his earlier unquestioning allegiance to the day’s psychological dogma. “I wince at my credulity when I told several hundred guileless undergraduates in 1954 that rejection by the mother could produce an autistic child.” He also speaks of his regret at wasting so many years ignoring the genetic contribution to behavior; he forthrightly admits that the omission confounded all his research. Although, like Kagan, few in his profession still believe in the environmental determinism that dominated psychology in those years, few have Kagan’s honesty in admitting the scope of their mistake.
Speaking about his changed perspective, Kagan said, “I was the classic politically liberal environmentalist who believed that genes had minimal effect on behavior. Now, I am quite a different person. My data has pushed me toward granting much more power to genetic mechanisms than I would have believed twenty years ago. I arrived here honestly, without prejudice, which is a good way.” In another interview he said, “For the first twenty years of my career, I wrote essays critical of the role of biology and celebrating the role of the environment. I am now working in the opposite camp because I was dragged there by my data.”
In his 1994 book with a subtly significant title, The Nature of the Child, Kagan speculates about ways in which the
genetic differences in brain chemistry of inhibited children might have evolved into the species. Noting that the thin body builds (ectomorphs) and blue eyes that are more typical of inhibited children predominate in northern Europe, Kagan puts forward the possibility that when humans migrated from Africa and arrived in northern Europe some forty thousand years ago, evolution might have favored mutations that would be beneficial in the more challenging cold environments. His experiments had shown that inhibited behavior is linked to a greater efficiency in the sympathetic nervous system and an increased production of a major neurotransmitter, norepinephrine. Kagan wrote: “Because the metabolic steps in the manufacture of norepinephrine are mediated by several different enzymes, some of which are controlled by one or a few genes, it is possible that such a change in DNA occurred.”
Not only was Kagan tracing a human behavioral facet, inhibition, to specific genes, he was also speculating about evolution’s role in bestowing those genes upon certain groups of humans. Whatever weight the theory might have, for the field of behavioral genetics it was exciting to have a mind of Kagan’s caliber and a psychologist of his experience to be thinking at last in genetic-evolutionary terms.
KENNETH KENDLER, a wiry, fortyish psychiatrist at the Medical College of Virginia, is another prominent researcher in behavioral genetics, or more specifically in his case, psychiatric genetics. Kendler is seeking evidence of genetic underpinnings to mental disorders—primarily anxiety, depression, and schizophrenia. In the early nineties he completed a major study on alcoholism in women. Although a generation younger than Jerome Kagan, he also came through his education at a time when environmentalism held sway. In American psychiatry this meant psychoanalysis, which focused on childhood experience, that is, the environment. It ruled out inheritance, some would argue, to a degree Freud never intended.
Kendler was aware that in the first half of the century, many distinguished European psychiatrists stood aloof from the Freudian-analytic Anschluss and continued to investigate biological, neurological, and genetic causes of mental illness. With no effort Kendler could name all the most prominent Europeans who kept the physiological torch alive throughout the analytic heyday—Emil Kraepelin, Ernst Rudin, Wilhelm Wundt, Alois Alzheimer (“he was looking for schizophrenia, but found something else”), Elliott Slater, Franz Joseph Kallman, Eric Intermutter, Eric Stromberg. Not only could Kendler name all these now obscure scientists, but he could also state under whom they studied, their areas of specialty, where they migrated with the neurological message, and their batting averages on advancing understanding of biological or genetic components to mental illnesses.
After doing his residency Kendler became one of a growing number of young American psychiatrists who lost faith with the analytic schools and began investigating more physiological approaches to mental illness. (A number of developments converged to bring about this change of direction in Kendler and many like him and will be examined in chapter 10.) A big part of his interest in schizophrenia stems from his belief that it causes more suffering than any other illness (primarily because of the large numbers of people affected, both the afflicted and their families), but also because it is a life sentence. Kendler estimates that in the 1990s there are between twenty and thirty major research projects in the U.S. aimed at finding the genes for mental illnesses. “That’s an industry,” he commented.
In Ming Tsuang’s 1997 book, Schizophrenia: The Facts, the author summarizes the large amount of work done on schizophrenia, including his own, and concludes that while there is a genetic component, it is not as strong as most experts had believed. Although no one is yet certain of the other causal factors, the suspicion is that it is something prenatal, a viral infection in the womb, a head injury, or a faulty oxygen supply. There’s no mention of the “refrigerator mother” (a leading culprit for the Freudians) or similar psychological traumas suffered during childhood.
Other projects Kendler has taken part in were a study of bulimia and a study of sleep disorders; both afflictions were found to have mild heritabilities. He also coauthored a paper that sought a connection between major depression and smoking. It concluded that while a relationship definitely could be found between the two phenomena, it was not a causal one. Instead, the conditions most probably resulted from genes that led to both behavioral manifestations. His main work of recent years has been in studying various affective disorders in women—anxiety, depression, alcoholism, and phobias. This research culminated in a barrage of papers in 1992 written with colleagues in Virginia, at the University of Michigan, and at Washington University Medical School in St. Louis.
The studies were based on female reared-together twins located through the Virginia twin registry, and the numbers of twins were large, ranging from one thousand to over two thousand. Females were chosen rather than males because they have “substantially higher prevalence rates for mood and anxiety disorders.” The studies were based on personal interviews with each twin, a far costlier method for obtaining data than the often criticized self-report questionnaires. The papers that resulted from the study contained detailed accounts of the recruitment methods, definitions of the conditions, and the way in which the statistics were analyzed.
One paper gave the results of a twin study of major depression in women. Using nine different definitions of depression, 1,033 women were measured for each one. The concordance rates never went above .49, some substantially lower. But that the identical twins had consistently higher concordance rates than the fraternal twins was taken as solid evidence that “genetic factors play a dominant, but not overwhelming, role in the cause of depression.” It was also determined that when the environment was a causative factor, it was an environmental element specific to the individual, not an element common to the entire family.
Similar results were reported in papers on generalized anxiety disorder, again evaluating 1,033 women and coming up with a modest heritability estimate of .30, which in itself was of borderline significance. Still, the consistently higher concordance of MZs over DZs proved that shared family environments had almost no effect; the variation came instead from environmental experiences specific to one twin. Without actually saying it, this specifying of nonshared environmental experiences as causes for depression had the effect of ruling out upbringing, to the degree that twins raised in the same home had similar upbringings. The studies might be summarized by saying that major depression and anxiety disorders do not result from upbringings, which twins share, but rather from genetic factors working in concert with life events and other environmental circumstances specific to one twin but not the other—and this might include the prenatal environment.
The Virginia group also published a paper at the same time on phobias in women that was based on over two thousand female twins. The heritability of susceptibility to phobias was found to be between .30 and .40—not high, but certainly high enough to reveal a genetic component. The study discovered, however, a significant difference in the four types of phobias investigated, to the point that one type, agoraphobia (fear of open spaces), seemed to have little relationship to the other types. It had a higher heritability and a lower susceptibility to specific environmental events. Other phobias, a fear of snakes, for example, might be activated in the person with a genetic leaning toward a phobia of animals in general but was triggered by a nasty run-in with a rattlesnake. Agoraphobia, on the other hand, appeared to be either present or not and relatively unaffected by experience or the environment, although the person fearing open space would obviously be happier living in a big-city apartment than on a North Dakota ranch.
Later in 1992, Kendler’s Virginia group came out with a paper on inherited factors in alcoholism in women, based on 1,030 female twins. Using three different definitions of alcoholism that separated out levels of dependency, the Virginians found in each category a substantially higher degree of genetic influence than in other conditions Kendler examined. Those studies had turned up heritabilities in the .50 to .60 range. His pa
per cited a number of earlier twin studies on alcoholism, most of which dealt with men (the majority were recruited through lists of people who at one time had been hospitalized for alcoholism). Kendler’s sample of women was found through a population-based twin registry. In addition, all of his subjects were interviewed face-to-face, whereas previous studies had relied on self-report questionnaires. The earlier studies with men had all indicated a meaningful genetic component, but alcoholism often manifests itself differently in men and women (age of onset, duration, and so on), so it was thought that the male genetic findings might not apply to women. Kendler’s study established that they do.
Scientists like Kendler, Kagan, Gottesman, and McClearn have for years now been plugging away at broad traits and behaviors—timidity, depression, alcoholism, schizophrenia—that affect large portions of the population. Their findings were later substantiated by the Minnesota twin studies. Although Bouchard and his colleagues were using a different method, reared-apart twins, they were looking for the same things, the same influences—and finding them. The far larger numbers of reared-together twins needed to produce statistically valid conclusions made the earlier studies far more cumbersome and laborious. Also, lacking the juicy oddities of the separated identicals, the Kendler-style studies didn’t receive the media attention that Bouchard had. But their painstaking efforts laid the groundwork for the Minnesota Twin Study and all subsequent quests for behavioral genes. They were the pioneers who proved that with many of the most common psychological problems, genes were often involved.
NINE
STARS OF THE NEW FIELD
OVER HER THIRTY-YEAR CAREER, Sandra Scarr has built a reputation as one of the country’s leading psychologists, having worked at Harvard, Yale, and the universities of Pennsylvania and Virginia. Like Jerome Kagan, she is a major figure in the child-development field and has done a number of studies that relate to the politically loaded subject of day care. More recently, she has emerged as an influential theorist of behavioral genetics and one of the most formidable adversaries of the environmental determinists. Unlike most of her behavioral genetics colleagues, who maintain a scientific dignity in their debate with critics, Scarr doesn’t hesitate to voice her exasperation with tactics she sees as unfair and obstructionist. Where others might characterize an opponent’s view as “unsubstantiated,” Scarr is more likely to call it “nonsense.”
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