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In this article I will attempt to debunk one of the great “scientific” smoke and mirrors shows of the past half century—the claim that stories of reunited separated MZ (monozygotic, identical) twin pairs indicate that heredity plays a major role in causing human behavioral differences. Many of these pairs were supplied to journalists by researchers of the Minnesota Study of Twins Reared Apart (MISTRA), which was carried out between 1979 and 2000. Stories about such pairs, which include the “Jim Twins,” the “Fireman Twins,” the “Giggle Twins,” the “Nazi and the Jew Pair,” and the “Necklace Twins” have been told and retold since 1979. These stories, which are often used to sell the false ideology of genetic determinism, have entered the public imagination in a way that academic research results never could.
Suppose we read about a reunited pair said to share remarkable similarities. It is claimed that they share the same taste in food, the names of their children, similar job preferences, similar quirky habits, and so on. What should we conclude? Certainly, this story is interesting. But does it also provide information about genetic influences on human behavior? At first glance it appears that it would. After all, these are two people who grew up apart yet share a remarkable set of similarities. What else besides the genes they share could account for these similarities? The psychologist David Moore cautioned, however, that in the “absence of an enormous amount of thought about twins, it is extremely easy to draw such erroneous conclusions.”
Read full, original post: “Bewitching Science” Revisited: Tales of Reunited Twins and the Genetics of Behavior