One brother’s eyebrow piercings and the other’s tattoos of his ex-girlfriend’s name helped friends and relations identify them. Before that fateful night at a family party, the brothers had arguments about silly little things like all brothers do. They soon made up, shook hands and put it behind them. But this time, one twin stabbed the other twice, leading to his death.
At first, this violence seems contrary to the close bond twins develop in the womb—even more so for identical twins. But twins can behave in completely different ways. A mouse study showed how small changes in behavior can lead to larger ones and even change the brain.
Studying the difference between twins remains a favorite tool of behavioral geneticists. Researchers have used twin studies to try to disentangle the environmental and genetic backgrounds of many traits in people, including aggression, intelligence, schizophrenia, and alcohol dependence.
As behavioral genetics enters a second century, the field's oldest research method remains both relevant and controversial.
(excerpt from Smithsonian, 1980, and Newsweek, 8 Nov, 1993)
The study at the University of Minnesota began with the Jim Twins. Other recently reunited twins participated as well. Twins shared jewelry wearing habits, children's names, phobias(claustrophobia is common among twins....something about being two in a womb maybe), fear of high elevations, thyroid disease, speech defects. In one case, both twins were gay, in another, only one was gay. One set of twins, Oskar Stohr of Germany and Jack Yufe of California were separated after their birth in Trinidad and grew up in very different cultural surroundings. Yufe was brought up a Jew by his Jewish father in Trinidad and Stohr was raised in occupied Czechoslovakia and went ot a Nazi-run school. Their attitudes were different, but Bouchard observed similarities in "temperment, tempo and the way they do things" as well as their idiosycracies. Both wore short, clipped moustaches, stored rubber bands around their wrists, and read magazines back to front. Both also shared the habit of sneezing loudly in public to attract attention. This latter trait is baffling. Some things remain inexplicable. "The results showed that such characteristics as leadership ability, imagination, vulnerability to stress and alienation were largely inherited." However, traits such as aggression, achievement, orderliness and social closeness were fostered in the home environment. Some twins turned out very differently, too. One twin in the Minnesota study grew up to be a "stellar pianist" in a non-musical adoptive family. Her sister, adopted by a piano teacher, never took to the instrument.
Some characteristics thought to be environmental, such as phobias, may well have a genetic componant. Twins raised apart may actually be more similar than those raised together because pairs brought up together can emphasize the differences between them. Some critics speculate that twins' different environments have been inadequately studied and that adopted twins might not be an accurate sample because the circumstances of adoption may affect behavior. Bouchard concludes, "In a sense we're tampering with the idea of the importance of the family in child-rearing. Our findings suggest that the subtle differences between and within families are not as important as people have thought in determining interests, abilities and personalities."
What do you think influenced your family relationships?