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In his summary of these heroic efforts on the part of the behavioral geneticists to meet this frequent objection of the environmentalists [that identical (MZ) twins develop similarly because they are treated more similarly than fraternal (DZ) twins], [Kenneth] Kendler made no mention of the complete substantiation these studies have received from the Minnesota and Swedish reared-apart twin studies, which lack the potential pitfall of different MZ-DZ upbringings in the same home. He laboriously showed that the one complaint has no basis in fact. It would seem to put to rest once and for all this one complaint and force the critics to find different ones.
This was not to be the case. For more than ten years after Kendler’s paper, opponents continued to cite the possibility of different upbringings given identicals as opposed to fraternals as invalidating twin studies. As late as 1994, the objection was raised in the pages of Scientific American. Sometimes the criticism is not alluded to directly. When other critics referred darkly to the “seriously flawed” nature of twin studies that compared monozygotic with dizygotic twins, more often than not the unnamed flaw turned out to be the one Kendler and others had refuted a decade earlier. And there is no possibility the critics who keep resurrecting this charge are unaware of the refutation. Each time the flaw is cited in print, a weary behavioral geneticist will write a letter to the editor pointing out the research that obviates the complaint, but the critics continue to make it year after year.
As an outsider, I came into this field believing scientists were simply truth seekers, men and women dedicated to discovering the functioning of the world around them, to understanding the givens. I saw them as driven by profound curiosity. It was, therefore, disheartening for me to learn that many scientists with broad reputations do not place truth at the top of their agendas and react in sadly unscientific ways when confronted with evidence they feel threatens their ideological positions. Aware of the scientific rules, they first attempt to discredit with counterarguments, but when these are shown empirically to be invalid, they simply pretend that the evidence they were unable to shoot down doesn’t exist. Such selective memory permeates the behavioral genetics debate. In the nonscientific world we have a word for such behavior: dishonesty.
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