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

the most famous boasts in psychology. Of course, the social implications of Watson's workespecially concerning race and class differenceswere shattering. If people were merely creatures of their environment, and not of their genes, then society imposed these differences, rather than simply reflecting them. Twentieth-century liberalism was born in the crusades

 

Page 23
for social reform that were spawned in part by these behaviorist ideals. The parenting guides of Benjamin Spock carried the behaviorist philosophy into the family. Generations of parents assumed responsibility for their children's talents and defects. Charles Fries did the same for education, instilling the ideal of universal equality as a goal of standardized schooling. Psychotherapy and self-help books became entrenched features of American culture. All these defining trends of modern society arose from the behaviorist doctrine that environment created individual differences.
Watson confronted the question of identical twins by drawing from the very slim literature on twins reared apart available to him in the 1920s. He cited three cases in which twins who had been separated in childhood and lived in different environments were later tested and found to differ significantly in certain respects: one set of twins showed a marked difference in motor skills, another set differed in personality, the third in intelligence. "Suppose we were to take individual twins into the laboratory and begin rigidly to condition them from birth to the twentieth year along utterly different lines," Watson remarked. "We might even condition one of the children to grow up without language. Those of us who have spent years in the conditioning of children and animals cannot help but realize that the two end products would be as different as day is from night."
Watson found an enthusiastic disciple in a young man named B. F. Skinner. During the war, while Mengele was trying to torture the secrets of genetic behavior out of his captive twins, Skinner was at the University of Minnesota teaching economics to rats (who could "buy" food with marbles), and training pigeons to pilot missiles, hoping they could be used instead of humans to conduct warfare. Skinner had refined Watson's

 

Page 24
principles of behavior to a level of considerable sophistication, as his animal experiments proved, and he hoped to extend his experimental insights into what he called a technology of behavior. He believed that all behavior is genetically based, because we are nothing more than the product of natural selection, but he disputed the notion that there are separate genes for altruism or criminality or any other character trait. What our genes do give us, Skinner reasoned, is the capacity to adapt to our environment. People are not innately good or bad; like any other organism they are determined by their environment. He attacked the notion of individual responsibility. It makes little sense, he believed, to hold people to account for their actions. If one wants to change behavior, then design a different environment. Skinner began the movement toward programmed instruction in public schools, which he expected would cut in half the amount of time required to learn a specified body of material, leading some enthusiasts to predict that eleven-year-olds would soon be earning their Ph.D.'s.
Today, few on either side would argue that we are exclusively the creation of nature or the reflection of nurture. The discussion has evolved into a statistical war over percentages: how much of our personality or behavior or intelligence or susceptibility to disease is attributable to our genes as compared to environmental factors, such as the family we are born into or the neighborhood we live in or the years of school we attend. The fulcrum upon which one side rises while the other falls is the concept of heritability, which was first defined by the biologist J. L. Lush in 1940. Heritability, he said, is the fraction