Born That Way

by William Wright

  Looking at name matchups in other twin sets, no one ever claimed a fashion in James Alan and James Allen or the two Louises of Bridget and Dorothy. But such name matches occurred repeatedly. With the high frequency among twin sets of a phenomenon for which a “rational” explanation makes little sense, I feel a degree of freewheeling theorizing is justified, if not to explain the phenomenon, at least to bring an explanation within shooting range.

  In his book Nature’s Mind, Michael Gazzaniga, who was formerly the director of the Center for Neurobiology at the University of California at Davis and who is now at Dartmouth, hypothesizes that the brain’s eleven billion neurons are not just broken down into two minds, the conscious and the subconscious, but many minds, perhaps as many as a thousand modules all functioning independently. For me, this created a picture of the brain as a large office building with many companies all following their own pursuits, occasionally interacting as they do business with one another, all acting in concert only for major events like a fire or a terrorist bombing.

  Brooding about the twins’ selecting the same names, I pushed my metaphor further. If the office building is converted to the Pentagon, I began to see Gazzaniga’s thousand minds as an army of officers, all overseeing diverse operations. At the end of a long corridor is the cubbyhole of a minor lieutenant who has only one duty: He is in charge of naming things. While the brain’s panels of high-ranking brass make major decisions about logistics or battle strategies, the lieutenant sits idle, indifferent, bored, his phone silent. But when it is time to name something—a new base, a jet fighter, a radar system—this highly compartmentalized bureaucrat springs to action. That’s all he does, name things when the need arises. Unfortunately, however, he is a fellow of almost no imagination. He likes a handful of names and that’s it. When asked to name a missile launcher, a tank, or a base mascot, he consults his name repertoire and comes up with one of his handful of possibilities.

  If somewhere there existed a clone Pentagon, Canada’s for instance, that was identical in every aspect, including the naming lieutenant in his cubby hole, it is conceivable that this minor officer, presented with similar items needing names, might occasionally arrive at exactly the same name for the same object. My analogy is of course preposterous, and grievously debases Gazzaniga’s splendid brain model of a thousand brains. (He cannot even be blamed for the edifice analogy.) On the other hand, wild phenomena like two terriers named Trixie call for wild theories. Science is, at this point, so far from understanding such phenomena, it might require a few wild leaps to bring us anywhere near an accurate explanation.

  (It is not hard to get carried away with my brain/Pentagon metaphor. As I write this, I am sitting alone in a pleasant house in Bucks County, Pennsylvania, where I know no one. I chose the locale because it seemed a good place to write. I discovered, however, that for every other aspect of my life, the isolated house was a dubious choice. I saw an explanation in the Gazzaniga paradigm. I have a committee of, say, 50 brains that are in charge of sound career decisions like choosing optimal locations for work. They put me in unfamiliar country in a preemptive burst of career responsibility. After the move was made, however, my other 950 brains realized what had happened and cried with one voice, “What the hell are we doing isolated out here in cow country?”)

  With or without recourse to such whimsical flights, somewhere in Gazzaniga’s brain theory may lurk the beginnings of an explanation for all the reared-apart twin parallels. If, as he postulates, our mentalities are compartmentalized into many independently operating mechanisms, it is conceivable that a number of these are more susceptible to genetic influence than others. And if it is demonstrated that genes are, in fact, involved in such specific behaviors, a number of genes would undoubtedly be involved. This would greatly reduce the chances of such phenomena occurring in fraternal twins. Just as in a game of poker, you might have in your hand the same number card that another player has in his—a three, say, or an eight—but to have all five of your cards numerically match all five of his would be extremely unlikely. As mentioned above, remarkable behavioral matches were, in fact, all but nonexistent among the fraternal twins tested.

  In the same way, striking personality facets shared by a set of reared-apart twins rarely turned up in other family members. Pondering this, Minnesota’s David Lykken worked out a theory that he called emergenesis and published it in a 1982 paper which later was his inaugural address as president of the Society for Psychophysiological Research. Lykken believed that for certain traits to appear at all, it required a complex combination of genetic elements, every one of which was essential for the trait to appear.

  This was different from the well-known genetic process of epistasis, which refers to interactions of genes to produce a variation. Lykken’s process was an all-or-nothing bouquet of gene interactions that might produce a complex, distinctive trait such as musical genius or great facial beauty in identical twins but would not show up to any degree in other relatives as they didn’t have all the sine qua non genetic pieces. Lykken also suggests this genetic process might explain that the mathematical genius Karl Frederich Gauss could be born to a bricklayer and a peasant woman of modest intelligence and that his children showed none of his genius. It appeared that he represented a onetime configuration of genes, each one of which was essential for the brainy result, and that probabilities dictated could only have been duplicated in an identical twin.

  Given the genetic card-shuffling during meiosis—when half the mother’s genes mix with half the father’s to produce the child—the chances of an offspring receiving the precise configuration that produced such a rare trait in the parent is extremely low. Likewise, chances are extremely low that if one child has the rare configuration any sibling or any other relative would have it. It might require twenty-eight genes to produce Cindy Crawford’s supermodel face. Her sister might have all but one of those genes and be superplain.

  Although Lykken’s emergenesis theory suggests an explanation for the identical behaviors, neither he nor the others on his team were prepared to hypothesize a specific genetic basis to these phenomena and instead limited themselves to reporting them and allowing others to infer what they wished. But granting some genetic basis, however improbable and elusive, the twin oddities would seem to fit Lykken’s model, in that there had been no reports of such odd parallels appearing in other members of the twins’ families: no backward-bathing relatives, or even sideways bathers; or among the Jims’ relatives, no semicircular tree benches; and for Jack and Oskar, no holiday dinners with relatives faking coughs or sneezes. These phenomena occurred only in the twins; no one else came close. Because of their uniqueness, the twin-shared traits, with their thundering specificity as well as the absence of such similarities in fraternal twins or in other family members, may well be as much a product of Lykken’s emergenesis as facial beauty or mathematical genius.

  EIGHT

  OTHER BEHAVIORAL GENETICS STUDIES

  BECAUSE OF THE EXOTIC NATURE of Bouchard’s reared-apart twins, the Minnesota study received most of the spotlight the popular press allotted to behavioral genetics. The general public, in fact, had little idea what behavioral genetics was or that research in the field had been under way for two decades in universities around the United States, Europe, and Australia, all turning up solid evidence of genetic influences on personality and behavior. One reason was the lingering distaste for the idea that genes have anything to do with who and what we are. Another was the laborious, undramatic methods used by the studies. Bouchard’s exotic reared-apart twins not only provided more conclusive evidence, they were in themselves more press-worthy.

  Except for a large reared-apart twin study in Sweden, the other genetic studies on human behavior have been based either on comparisons of adoptees with unrelated siblings or comparisons of identical with fraternal twins—all reared in the same homes. In some studies, the adoptees were also compared with both their adoptive parents and their biological parents, produc
ing data from which a number of genes-or-environment inferences could be drawn. Whatever the methods, all the studies were efforts at teasing apart genetic from environmental influences to arrive at estimates of the percentages of heritability for specific traits and aptitudes.

  Irving Gottesman has long been considered one of the grand old men of behavioral genetics, an epithet that says more about the youth of the field than the age of Gottesman, who was born in 1930. Because his doctoral dissertation, The Psychogenetics of Personality (University of Minnesota), was written in 1960, when genetic theories of behavior were still anathema in most parts of the academy, this definitely establishes him not just as a pioneer but as a courageous one. Although a psychologist rather than a psychiatrist, Gottesman has had a lifelong interest in the genetic basis of schizophrenia and in the mid-1960s worked with the famous British twin researcher James Shields on schizophrenia in twins, publishing with him a number of papers and, in 1972, a book, Schizophrenia and Genetics.

  Another prominent psychologist, Gerald McClearn, having worked for years on the genetics of animal behavior, has concentrated increasingly on human behavior in recent years. Along with J. C. Defries, he was an initiator of the behavioral genetics studies at the University of Colorado and later continued work in this field at Penn State. McClearn is also a participant in the separated-twin study at Stockholm’s Karolinska Institute and is one of the designers of the MacArthur Longitudinal Twin Study (twins measured at different ages), which is supported by the John and Catherine MacArthur Foundation. In 1973 McClearn and Defries wrote An Introduction to Behavioral Genetics, then in 1960 the two scientists, along with Robert Plomin, wrote Behavioral Genetics: A Primer. Perhaps because they started out in a climate hostile to their young field, these psychologists have consistently turned out work marked by meticulous methodology and scientific caution.

  In the United States, one of the most venerable behavioral genetics studies is the Louisville Twin Study started at the University of Louisville in 1963. Each year since its inception, the Louisville study recruited some two dozen reared-together twin sets to produce a sample now totaling more than five hundred pairs of both fraternal and identical twins. The study, headed in recent years by R. S. Wilson, is ambitiously longitudinal, with twins tested at three-month intervals their first year, six-month intervals until they are three, then annually thereafter. In the early years of the study, the twins were assessed for I.Q. development and physical growth, but in 1976 the focus shifted to temperament.

  The study is ongoing, but results so far show correlations on mental development (the Bayley Index) of .68 for MZs and .63 for DZs, only a slight difference. Correlations for nontwin siblings, however, are far lower, about .31. With temperament, on three different traits measured (by the Bayley Infant Behavior Record test), the correlation for extroversion was .43 for MZs, versus .07 for DZs. For task orientation (a measure of concentration) the correlation was .49 for MZs, versus .23 for DZs. Both of these results showed significant genetic influence. On the third trait measured, activity (level of motion), no significant amount of genetic influence was found.

  The Louisville group has also recently released findings from a series of tests based on videotape recordings of infants’ behavior in laboratory situations. With only thirty pairs the results so far have been inconclusive except for one measure, a trait called behavioral inhibition. For this the MZ pairs correlated .71 as opposed to .25 for the DZs, an indication of a remarkably high degree of genetic influence. This jibed with Jerome Kagan’s work at Harvard on timidity in infants, which is discussed later in this chapter.

  The most comprehensive and long-ranging studies of twins and adoptees have been in progress at the University of Colorado, most especially a longitudinal twin study, one of a number of MacArthur-funded research projects concerned with childhood transitions. It is increasingly apparent to researchers that it is not simply a matter of genes’ influence being present or absent with behavioral traits, but that they kick in or go dormant at different periods throughout a life. This gives importance to the longitudinal studies that measure the same twin sets periodically over a number of years.

  Colorado’s longitudinal study is a collaborative effort directed by Robert Ende and a group of Colorado colleagues and includes as well Jerome Kagan of Harvard, Steven Reznick of Yale, Joseph Campos of the University of California at Berkeley, Robert Plomin of Penn State and London’s Institute of Psychiatry, and Carolyn Zahn-Waxler of the National Institutes of Health. That this landmark behavioral genetics study is a combined effort of the N.I.H. and five of the nation’s foremost universities belies the critics’ efforts to depict behavioral genetics as a fringe discipline.

  Before launching this ambitious twin project, Colorado had run an important longitudinal study of adoptees that began in 1975 and was completed in 1983. It was based on 245 families with adopted children and a control group of another 245 families with nonadopted children. All the children were assessed annually, from ages one to four, in cognitive abilities, personality, interests, and talents. They were tested again at seven, nine, and sixteen years, and their performance was compared with results of similar tests administered to adoptive parents, biological parents, and unrelated siblings. This study showed a substantial genetic influence on mental development at twelve months and—because of negligible correlations between unrelated siblings in the same homes—virtually no influence from shared environment. In the measurement of temperament, the Colorado study showed genetic influence on all three of the traits measured, unlike the Louisville study, which had found it in only two.

  Among the intriguing findings to be extracted from Colorado’s wealth of data was that for certain traits the fourteen-month-olds showed considerable genetic influence, for other traits almost none. When the same children were measured later in life, significant heritabilities were found for every trait. This clearly demonstrates that behavioral genes turn on at various ages. This study and other similar ones have turned up the curious fact that when the genetic component of a trait is shown to vary with age, the variance always increases, never decreases. This is surprising in that the older a child is, the more opportunity the environment has had to work its influence. But instead of gene influence diminishing, as one would expect, it increases with age. This is bad news for those who dislike sharing personality traits with their parents. With years, the similarities will probably increase. The delayed unfolding of genes also gives new resonance to the expression “finding oneself.” It may be more a matter of waiting for oneself to arrive.

  In 1986 the University of Colorado initiated an even larger longitudinal study, one that included 300 pairs of reared-together twins who will be assessed at fourteen, twenty, twenty-four, and thirty-six months for cognitive abilities and an array of mood and temperament characteristics. In a preliminary 1992 paper reporting on the results at fourteen months, the data showed the identicals testing consistently more concordantly than the fraternals. Persuasive as their results are for a genetic contribution to the traits measured, they end their paper by pointing out weaknesses in their twin design, a self-attack as destructive as the usual attacks from critics on gene-behavior research. While undoubtedly included to forestall this very thing, it has an undermining effect that is puzzling.

  THE THIRTY-FIVE YEARS of work in developmental psychology of Harvard’s Jerome Kagan has made him a leader in his field. His main area of interest has been the inhibited and uninhibited child—primarily because this is an adult characteristic that is also observable in very young infants and can be monitored over years. His numerous writings on this and other subjects, his scientific dedication, and his cant-free style of communicating have all combined to make him one of the most honored and respected American psychologists.

  Like most everyone of his generation, Kagan started out as a staunch environmentalist, a disciple of Skinner and Watson. When he decided to go into developmental psychology, it was not as an abstract quest for pure knowledge but
was colored by strong altruistic ambitions. This was a period when all behavior was considered learned, including the behavior that produced social problems. If psychologists could unravel the precise mechanisms of learning and pinpoint the environmental causes for children developing as they do, educators and social scientists would be positioned to improve society greatly by averting the developmental mishaps that lead to poverty, ignorance, and crime.

  Kagan’s first research was in 1957 at Antioch College, when he was brought in on an existing developmental study of inhibited children who had already been assessed in the first months of life. For his initial assignment, Kagan was asked to conduct follow-up interviews with the study group, who were now young adults. Along with his colleagues, Kagan was surprised to find that the children who had been extremely fearful as infants remained so throughout adolescence and into adulthood.

  He later recalled thinking how remarkable it was that the effects of the parents’ rearing during the first months of life could have such an indelible effect. So imbued was he with the environmentalist creed, he, like his colleagues, never entertained the possibility of a genetic explanation. When I interviewed him in 1994, Kagan, looking back on this period, said his blinkered vision was especially remarkable since in a nearby Antioch laboratory a team investigating heart-rate variations had found a connection between fearfulness and heart rate. While this finding strongly suggested a biological basis for fearfulness and a link between physiology and psychology, the researchers took the idea no further with a kind of “we don’t want to go there” reticence. The concept of fearful children having been born that way was totally alien to mainstream psychology in the 1950s. No one was born any “way”; we were all at birth tabulae rasae, innocent, raw, and ready for the world to do its worst. Such was the faith in the environment’s omnipotence in the heyday of behaviorism.