Read Twins: And What They Tell Us About Who We Are for Free Online

for the London school system. Over the next several decades, Burt founded child guidance clinics and a special school for the handicapped; he developed important new tests and surveys; he wrote a series of books that became landmarks in the rather new fields of juvenile delinquency ( The Young Delinquent ) and mental retardation ( The Subnormal Mind and The Backward Child ), which established his reputation as one of the world's leading educational psychologists. This was despite the fact that Burt showed little caution in betraying his class prejudices (describing, for instance, a lower-class white delinquent as ''a typical slum monkey with the muzzle of a pale-faced chimpanzee").
Early in his tenure, while working with the London schools, Burt began comparing IQ and scholastic achievement scores on twins and other kinship groups, eventually compiling an unrivaled collection of data on heredity and intelligence. In 1966, at the height of his eminence, he published an epochal paper on fifty-three pairs of identical twins who had been reared apart, a surprisingly large sample of such a rare population. He had accumulated the twins over a period of forty-three years. Separated twins are at once an experiment of nature and an experiment of society. Until that time, there had been only three substantial studies in the literature (Neubauer and his colleagues at the Psychoanalytic Institute had just begun their study). In theory, the average differences between MZ twins reared apart and MZ twins reared together should provide an unassailable measure of environmental effects; however, the environments in which the separated twins are reared may be similar in important ways. Burt's study was particularly stunning because he claimed to have analyzed the socioeconomic status of

 

Page 28
the wide range of households into which the separated twins were adopted and found that there was no correlation at all between themand yet the IQs of the separated twins were still very similar. No other study had provided such comprehensive data on the relation of intelligence to social class and social mobility. It appeared to clinch the argument that intelligence is an inherited characteristic and that there is little that can be done in the way of tinkering with the environment to change that.
Three years after Burt's separated-twin study, Arthur R. Jensen, a psychologist at the University of California at Berkeley, published a magisterial attack on compensatory education in the Harvard Educational Review . "How Much Can We Boost IQ and Scholastic Achievement?" the title inquired. Jensen's essay, which shook the educational establishment and became the subject of discussion on talk shows and in the White House, was partly based on Burt's work, which was then still untarnished by the allegations of fraud that later covered his work with controversy. In his article, Jensen addressed the racial implications of the genetic transmission of intelligence, and the implications were gloomy indeed. Scores on standardized intelligence tests repeatedly demonstrated that the average black IQ lagged one standard deviation (15 IQ points) behind that of whites. Using the twin studies, which showed the heritability of intelligence to be about 0.80, Jensen argued that the effort to improve IQ among blacks by enriching the environment could produce, at best, a marginal gain, since environmental factors could account for only twenty percent of the difference. He concluded that we should abandon traditional methods of classroom instruction that begin with the premise that people are fundamentally alike in their

 

Page 29
mental capacities in favor of a model based on genetic diversity.
Of course, there is not a single gene for intelligencepresumably many different genes contribute to the trait that such standardized tests measurebut then, there is not a single gene for height, either. "The simple polygenic model for the inheritance of height fits the kinship