Twins: And What They Tell Us About Who We Are (20 page)

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Authors: Lawrence Wright

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

BOOK: Twins: And What They Tell Us About Who We Are
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Page 132
in a maternity home, so that the developing child would not be harmed by drugs or alcohol. "As soon as the child is born, he is taken away and put in a foster home and put up for adoption," Lykken explains. After a second violation, the unlicensed mother would have to submit to a surgical implantation of a time-release birth-control drug called Norplant, which chemically sterilizes the woman for up to five years. Fathers would be tracked down and identified through DNA testing and made to pay a portion of their future salaries to support the children they helped to create.
Lykken's plan is a grandchild of Sir Francis Galton's nineteenth-century idea of parenting quotas, intended to cull the undesirables from Britain's genetic stock. Although even Lykken considers it unlikely that his licensing plan will become law anytime soon, it is social engineering like that that causes people to be terrified of behavior genetics. "A lot of social scientists are so scandalized by my proposals that they think I must be a Fascist," Lykken says. "But I consider myself to be a political atheist." Lykken is a well-respected researcher who is known for taking authoritarian positions on public policy. He has recently published a new book,
The Antisocial Personalities
, in which he contends that what turns children into sociopaths is not genes but the environmentparticularly an environment of a fatherless home and an illiterate mother. "It has become part of the received knowledge from twin studies in recent years that being reared together in the same home does not make siblings more alike, and that puzzles people. The one real exception to that is socializationlearning how to avoid breaking the rules that are necessary for living together," says Lykken. "We know that criminality runs in families. Thirty percent of arrestees have a brother already in the slammer. There's no question
 
Page 133
that a small group of chronic criminals who are responsible for sixty percent or more of crime in this country tend to come from the same areas, the same social classes, the same families. When you look at the home in which the typical juvenile delinquent grows up, you don't need a study in order to be convinced that this is a pathogenic environment. It's mind-boggling the kinds of homes in which several million American adolescents are currently developing into little sociopaths."
Lykken acknowledges that most of the unlicensed parents who would be penalized under his proposed measure would be black, since he says that illegitimacy is some six times higher among blacks than whites. "I think that is the explanation for the difference between black and white crime," says Lykken. "One-eighth of the population is responsible for one-half of the violent crime, but I think that is because such a high proportion of black males are reared without fathers. So if we could accomplish by some magic a reduction to a very low level of illegitimacy in both races, I think crime rates would plummet and would equalize between the races, and even the IQ differences would be smaller than they are. This is important to me because one of my three sons married an African-American lady and I have three African-American grandchildren."
Race and IQ have haunted the study of human genetics, because historically the IQ scores of blacks have consistently been lower on average than those of whites. At the center of the IQ controversy is Sandra Scarr, a former colleague of Lykken and Bouchard at the University of Minnesota who is now a professor of psychology at the University of Virginia. (She is also the past president of the Behavior Genetics Association and the American Psychological Society.) Scarr was one of the first researchers to conduct twin studies in minority racial
 
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populations. Brilliant and dauntingly prolific, much praised and often damned, Scarr has divided the academy because she has insisted on applying the insights of behavioral genetics to developmental psychology.
Early in her career, Scarr began studying why so many black children did poorly on tests and in school achievement. She wondered whether it was the result of socio-cultural disadvantage or genetically based racial differences. "I thought that there were only a few ways to ask that question," she recalls. "There was no point in documenting yet again that on average blacks score lower than whites. Just documenting that black children did poorly on tests, we already knew that. So I turned to testing black twins in order to look at the genetic and environmental variation within the black community."
It was a taboo question in the early seventies, when Scarr began testing black twins in the Philadelphia schools. Arthur Jensen's 1969 article "How Much Can We Boost IQ?" had stirred up a nasty debate by airing his theory that whites are genetically superior to blacks in intelligence. Two years later, Richard Herrnstein's article on IQ in the
Atlantic
rekindled the same debate. After watching the public pillorying of Jensen and Herrnstein when their articles appeared, Scarr decided that if her data supported a substantial relationship between African ancestry and low intellectual skills, she would have to leave the country. In fact, it didn't, and she remained, to become one of the most acclaimed and controversial of American psychologists.
One of the most striking findings from Scarr's early twin work was that, while studies had shown a closer correlation between the IQ scores of white identical twins than between those of white fraternals, the scores of both identical
and
fraternal black twins were similar. A set of black fraternal twins was less likely to
 
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diverge widely in intelligence; there was less likely to be one clever and one slow twin. Scarr speculated that the differences were suppressed by the depredations of the black child's environment. When she compared the IQ scores for white children at the bottom of the socioeconomic ladder, it turned out that environmental differences were just as controlling for them. Scarr's findings suggested that inner-city black childrenand white children in the same severely deprived circumstancescould have the genes for a higher intelligence than their environment permitted them to express. In 1972, soon after Scarr began teaching at the University of Minnesota (a move that seems almost inevitable for anyone interested in twin studies), she and one of her students, Andrew Pakstis, decided to test Jensen's theory that intelligence differences between whites and blacks were genetic in origin. Scarr and Pakstis reasoned that if Jensen was right, children of mixed black and white parentage (which is true of most African Americans) would score higher on IQ tests according to their proportion of white ancestry. But subsequent tests of Phil-adelphia twins found no relation between intellectual-performance scores and the degree of white genetic background.
Then Scarr, along with Richard A. Weinberg, a psychologist who worked with her at Minnesota's Institute of Child Development, decided to conduct an adoption study, which is another way of deciphering the relative contribution of genes and the environment on the formation of human intelligence and personality. Adoption studies are a natural complement to twin studies, since the one investigates genetically unrelated people raised in the same environment, and the other examines genetically identical people raised in the same or (in the case of separated twins) different environments.
 
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Scarr and Weinberg looked at 130 black and mixed-race children, ranging in age from four to twelve, who had been adopted by well-off white families. The average IQ of these children was 106, which was higher than the mean of 100 for the general population and well above the average score of 90 for black children in the region. The earlier the children had been adopted, the better they fared. Scarr and Weinberg estimated that the scores of these early-adopted children could be about twenty points higher than those of comparable children reared in the black community. It seemed clear that the environment influenced IQ considerably. Being reared in the culture of the tests and the schools apparently made a large difference in achievement.
At the same time, however, Scarr and Weinberg were studying a group of white adolescents, ages sixteen to twenty-two, who had been adopted in early infancy and were at the end of their childhood. The adopting families were all white, across the middle range of the socioeconomic spectrum.
*
"We were interested in seeing the cumulative effects of the family-rearing environment on IQ scores," says Scarr. "We were astonished at the results." The hypothesis of the study was that if the family environment mattered, then at the end of the child-rearing period adopted children would show the maximum effects of the advantages and disadvantages of the families that had taken them in. The IQ scores of the adolescents were about the same as the black and interracial children in the other study. The disconcerting revelation from the adolescent study was that after adopted children and natural children were reared to-
*
One weakness of adoption studies is that they underrepresent families living in poverty, since such families are rarely permitted to adopt children. Therefore, inferences about the environment can only be drawn from the broadly constituted middle class.
 
Page 137
gether for eighteen years, the IQ scores of the adopted children bore
no relation at all
to those of the natural children in the same family or to those of their adopted parents.
*
''We had expected children reared in the same family to resemble each other
more
in IQ and personality than the young children in our transracial study, but we were dead wrong on both counts." The young black adopted children in the other study were more similar to their white siblings than the adopted adolescents in the new study were to their siblings, despite the fact that the adolescents had spent their entire childhood with their adopted families and were of the same race. "This was really interesting," says Scarr. "First we were amazed in the adolescent-adoption study that we did not find any resemblances among people unless they were genetic relatives. This did not jibe with previous adoption literature or with our own transracial adoption study. We tried to figure out why adolescents bore so little resemblance to their adoptive families."
Scarr found that children in the same family who were genetically unrelated were alike in early years but grew to be different over time. They became more like their biological parents, whom they didn't know, than like the adoptive parents who raised them, not only in social attitudes, vocational interests, and unexpected personality features, such as prejudice and rigidity of belief, but also in IQ. A follow-up study of the black and mixed-race children who were adopted into white homes found that by adolescence their IQ scores had fallen to a point slightly above what would be the average for their racial and ethnic mixture in the area. It was similar to the progression
*
A well-known Texas adoption study found similar results: moderate IQ correlation between genetically unrelated siblings in childhood dropping to essentially zero by late adolescenceand what is more, they were the
same children
measured at two ages (ten years apart).

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