Free Twins: And What They Tell Us About Who We Are by Lawrence Wright Page A

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