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Authors: Lawrence Wright

Tags: #Family & Relationships, #Siblings, #Science, #Life Sciences, #Genetics & Genomics, #test

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a part of twin lore; twins frequently report that they experience sharp pain when one is injured, or that they know when the other is about to call; some have even reported being able to see out of the other twin's eyes when they are experiencing some dramatic event. These suggestive psychic connections between identical twins could explain some of the mysterious synchronicities, but they have been rarely tested and never confirmed. Moreover, many of the twins had not been aware that they had a genetic companion in the world.
Bouchard throws up his hands when he talks about the coincidences. "We had a lot of discussions about how you could do anything with that information, and it turns out it would be a massive, massive job. It's a big world with lots of possibilities. For example, take the names of the kids." He was referring to the fact that several twins who had been raised apart gave their children identical or highly similar names. "We know names are not randomly distributed. They come in waves. They reflect popular taste. When Jack Kennedy was president, there were a lot of kids named Jack. We know that these are nonrandom events. And so the probability that two people have the same name can't be validated against some random action. What you need is a population of couples the same age as the twin couples with their kids, and then you'd need to know the frequencies of all these names. Think about how much work you'd have to do to gather that kind of informationbut then you'd have to do it for everything! About the car they owned! About the beach they went to! What they named their dog! You'd have to collect that data from every pair. And then, what would it tell you?"
Those early sets of twinsthe Jims, the Giggle Sisters, the Nazi and the Jewcreated a sensation not only in the popular press but in scientific journals as well.
 
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Money, which had been so hard to capture in the early years of the Minnesota study, soon came along in the form of government funds and grants from private foundations that had an interest in twin research. Foremost among the foundations backing Bouchard's research is the Pioneer Fund, a New York foundation that has roots in the eugenics movement of the thirties and that has had a history of backing projects that advocate racial separatism. The Pioneer Fund has given the Minnesota project over $1.3 million, more than any other project in the fund's history. In the sixteen years since Bouchard met the Jim twins, his study of reared-apart twins has included 132 individuals who are identical twins; two sets of identical triplets; another two sets of mixed triplets (a pair of identical twins plus a fraternal third member); seventy-six individuals who are same-sex fraternal twins and twenty-six who are opposite-sex fraternals; plus more than a hundred other people who are spouses, friends, adoptive parents, and siblings of reared-apart twins. The youngest set of twins was eleven, the oldest seventy-nine. The center also maintains a substantial registry of reared-together twins, helps separated twins find their siblings, and provides information of interest to twins over its own toll-free telephone line (800-IMA-TWIN) for its still ongoing study.
At first, many of the findings seemed quirky, at odds with one's expectations of how personalities are shaped. Religious attachment, for instance, would seem to be largely a creation of the family environment. Even some very distinguished behavioral psychologists believed that religiosity had no genetic basis. However, when the Minnesota team studied religious interests, attitudes, and behaviors of twins reared apart, as well as twins reared together, they found that genetic factors accounted for about fifty percent. Religious affiliation, on the other
 
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handone's denomination or beliefwas largely environmental. As Bouchard and others extended their studies of personality, a pattern emerged: characteristically, about half of the variance in most measurable personality traits turned out to be genetic. For the commonly tested traits of extroversion, agreeableness, conscientiousness, neuroticism, and openness, Bouchard found the overall heritability to be 0.41. Other researchers found that the heritability of radicalism and tough-mindedness was 0.65 and 0.54; for authoritarianism the heritability estimate was 0.62. Genetic influences on occupational interests, on the other hand, were slightly less heritable.
Of all the twin pairs that have come to the university, there were only two "dog people"one showed her dogs and the other taught obedience classesand they were a reared-apart twin pair. Only two of the more than 200 individual twins who had been reared apart were afraid to enter the soundproof chamber in the psychophysiology lab unless the door was left open  again, an MZ pair, the same women who insisted on entering the ocean backward. There were the two men who independently offered a correct diagnosis of a faulty bearing on Bouchard's car, two fashion designers, two captains of volunteer fire departments, two who had been married five timesin each case, a pair of reared-apart identical twins.
One of the Minnesota researchers, David Lykken, tried to test the hypothesis that identical twins were sending telepathic communications to each other, which might explain some of the startling coincidences. He placed a pair of female identicals in separate sleeping chambers and monitored their brain waves through the night. At intervals, one twin would hear a recording of her sister's voice calling out her name"Mary! Mary! Mary!"two or three times. The twin in the other lab,
 
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at different times, would hear her sister calling out "Sue! Sue! Sue!" Lykken's notion was that telepathy might work better during sleep. Mary's brain waves would indicate that she heard Sue calling her; perhaps then she would respond by sending out some kind of mental signal that would register with Sue. The first pair of twins actually did seem to communicate as Lykken had predicted, but then he discovered an error in the computer program that made the effect seem far less significant. A British researcher on paranormal psychology, Susan Blackmore, found that twins who were placed in separate rooms and asked to draw whatever came to mind would often draw similar things, but if they were asked to draw a picture and psychically transmit it to the other twin, there was little evidence of telepathy. The conclusion that Blackmore drew was that while twins may seem clairvoyant, it is only because they are thinking the same thinga remarkable effect, but not the one she was studying.
Obviously, extrasensory perception would be a useful quality for espionage, so it is not surprising that the U.S. Central Intelligence Agency has performed experiments to determine whether twins have a significant ability to transmit knowledge telepathically. Twin lore is replete with anecdotes suggesting that illness or trauma in one of a pair of identical twins could be sensed by the other twin, even when they are far apart and unaware of the other's status. The unnamed CIA experimenters noticed that the brain's alpha rhythms can be elicited simply by closing one's eyes in a lighted room. They placed identical twins in separate rooms twenty feet apart and told them to open or close their eyes only on demand. Their brain patterns were carefully monitored. The experimenters theorized that eye closure in one twin should trigger alpha rhythms in both. Out of thirteen sets of
 
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twins, two sets produced the results that the CIA was looking for. None of the unrelated subjects involved as controls in the test showed any telepathic connection. "Extrasensory induction of brain waves exists between individuals when they are completely separated. It certainly is not a universal trait in all identical twins," the experimenters concluded. "Because of the paucity of controlled data, contrasted with the voluminous pseudoscientific and highly emotional information available in the realm of extrasensory perception, it appears unwise to draw any conclusions or to make any statements regarding these aspects of the current investigations." This provocative finding suggests that there is at least some basis for believing the stories twins so often tell about their telepathic awareness of each other when they are apart.
Twins also share genetic traits that do not run in families: they are idiosyncratic features that seem to be exclusive to identical twins. "Behavior geneticists have been talking for years about polygenic traits, like stature and IQ, that are determined by multiple genes in different locations on the genome, working together in an additive way," Lykken says. "But some traits may be determined by
configurations
of genes. For example, musical talent runs in families but singing ability does not." A singer requires talent, proper vocal apparatus, a musical ear, and perhaps certain features of personality that would encourage public displays. Each of these traits is partly genetically determined, which is why identical twins have such remarkably similar voices, but ordinary siblings seldom have voices that are really alike. Beauty, Lykken proposes, is another example of the configuration of various genetic traits that are not remarkable by themselves; traits of leadership and scientific genius may be as well. Perhaps the idiosyncrasies, the weird co-
 
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incidences, and the similarity of life events can be explained by the fact that identical twins are not just the sum of their individual genes but the product of many genetic constellations, which in a powerful, synergistic manner determine behavior, mannerisms, tics, social attitudes, marital relations, clothing choices, and political affiliations. Identical twins, in some respects, can be even more alike than we knew.
The mountain of data compiled by the Minnesota team, along with ongoing twins research in Boulder, Stockholm, and Helsinki, stunningly tipped the balance in the nature-versus-nurture debate. Bouchard and his collaborators assessed a variety of personality characteristics, such as a sense of well-being, social dominance, alienation, aggression, and achievement, which they described in an important article in the 1988
Journal of Personality and Social Psychology
. On the question of IQ, the Minnesota team found a higher correlation for separated MZ twins than most previous twin studies: 0.76, almost exactly the figure that Cyril Burt stood accused of fabricating. Identical twins reared together score 0.86, as much alike as the same person tested twice (0.87). In the personality domain, the Minnesota team attributed about half of the measurable variation to genetic causes. (These studies measure statistical differences within populations. They do not imply that fifty percent of any one individual's personality is genetically acquired.)
Bouchard's team compared the personality scores for separated MZ twins and separated DZ twins against the scores for twins of both types who had been reared together. They concluded that identicals reared apart were about as much alike asin some cases
more
alike thanidenticals reared together. Moreover, there was not a single one of those personality traits in which fraternal
 
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twins reared together were more alike than identicals reared apart. How could this be? Wouldn't twins who had grown up in the same family, gone to the same schools and churches, and been exposed to the same values and traditions have been similarly shaped by those influences? If, as the Minnesota team was claiming, half of the variance in personality in a population was genetic in origin and the other half was environmental, why wouldn't fraternal twins reared together be far more alike in their personalities than identicals reared apart?
The answer to this paradox had been suggested before, but not with the force of so much data. ''None of the environmental variance is due to sharing a common family environment," the Minnesota team asserted.
None?
Bouchard and his colleagues repeated the charge in an unsettling 1990 article in
Science
. "The effect of being reared in the same home is negligible for many psychological traits," the Minnesota team wrote. Even in social attitudes, such as religiosity and traditionalism, adult identical twins were about as much alike regardless of whether they had been reared together or apart. "We infer," the Minnesotans wrote, "that the diverse cultural agents of our society, in particular most parents, are less effective in imprinting their distinctive stamp on the children developing within their spheres of influenceor are less inclined to do sothan has been supposed."
Bouchard's findings confirmed a startling, much-debated adoption study that had been done at the University of Minnesota a few years before his twin studies began. Sandra Scarr and Richard A. Weinberg compared the IQs of adopted children with those of their adopted parents and their biological parents. As is typical in adoption studies, the IQs of the children were higher than those of their biological parents, but still strongly correlated. The inference usually drawn from this information
 
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is that the adopted parents tend to be of a higher intelligence and a higher social class than the parents who surrender their children for adoption, and that the improved scores reflect this enriched environment. Scarr and Weinberg pointed out, however, that the children's IQ did not correlate at all with the IQ or the social class of their adoptive parents. They concluded that most families provide "functionally equivalent" environments; in other words, a person could grow up in one family as well as another and still have, at the end of adolescence, the same IQ in either case. Scarr and Weinberg qualified their observations to point out that they were not talking about extremes of environment; children raised in truly deprived circumstances would no doubt show the effects. But the elevation in IQ that was supposed to follow the rise in economic status simply wasn't present. "Why are the relatively poor families rearing adopted children whose IQ scores are nearly as high as those in professional families?" they asked. "It must be that all of these seeming environmental differences that predict so well the outcome differences among biological children are not primarily
environmental
differences, but indices of genetic differences among the parents and their biological offspring." In other words, the lower intelligence of the lower working class was a result of their genes, not their situation. It was the same observation made by Francis Galton a century before.
Bouchard's studies began at a time when twin research was struggling to regain scientific respectability; now twin studies dominate much of the research in personality. Autism, for instance, was believed by the behaviorists to have been caused by "refrigerator mothers" who raised their children without enough affection; similarly, schizophrenia was supposed to have been generated by mothers who repeatedly placed their children
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