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Psychologist David Lykken, one of the Minnesota researchers, thinks the study will shove the pendulum further away from the "radical environmentalism" of those who believe the characters of children are more or less created by their parents and environment. Lykken says Test Pilot Chuck Yeager is daring because he was "genetically endowed with a low scale of fearlessness," a trait that might have been redirected or tamped down but not eradicated. Says Psychologist Nancy Segal, a member of the project: "Parents can work to make a child less fearful, but they can't make that child brave."
Adam Matheny of the Louisville Twin Study, the oldest of U.S. twin study groups, says the "mechanism for change is laid down the moment a child is conceived" and that the genes provide a "rough sketch of life." Some psychologists who stress the influence of genes on behavior often speak as if nurture were a by-product of nature. "All of us make our own environment," says Developmental Psychologist Sandra Scarr of the University of Virginia. Lykken makes the same point: "The environment molds your personality, but your genes determine what kind of environment you have, seek and attend to." Since the early 1960s, several twin studies have reported that identical twins reared apart are actually more alike than those raised in the same home. Scarr thinks the reason is that parents faced with identical twins try hard to stress differences between siblings. Says she: "Living with the same family seems to increase intellectual similarity and decrease resemblance in personality."
Some scholars, such as Princeton Psychologist Leon Kamin, fear that the Minnesota results will be used to blame the poor and downtrodden for their own condition. Political liberals have long believed that crime and poverty are largely by-products of destructive environments. As a result, they are usually suspicious of biological or genetic explanations for behavior. "These are very ambiguous data that can be interpreted any way you want to," says Kamin. "I'm not saying that anyone is falsifying facts or anything, just that we really know very, very little." For the Minnesota researchers and their allies, however, their study is just one more proof that parenting has its limits. Says Psychologist and Twin Researcher David Rowe of the University of Oklahoma: "Parents should be blamed less for kids who have problems and take less credit for kids who turn out well."