Findings
Although Prof. Segal does not put it in these terms, MISTRA yielded what amount to two different kinds of findings: quantitative and impressionistic. The former come from personality, intelligence, medical, and other testing, whereas the latter include the almost eerie, unmeasurable ways in which MZA twins are alike.
The first twin pair MISTRA evaluated was particularly striking. The two men met when they were 39, and found that both had been in law enforcement but were now working as firemen. Both had loved math in school and hated spelling. Both did woodworking as a hobby, and their favorite vacation spot was Pas Grille Beach in Florida. One had named his son James Alan and the other had named his James Allan. They looked very much alike, had the same smoking habits, and always held a beer can with a pinky under the can. Both had put on 10 pounds at the same age for no apparent reason.
Not all twins were so alike, but this book is full of astonishing similarities. In one MZA pair, one twin was reared in Germany and the other in Trinidad, and they had never met before they came to Minnesota for testing. When they arrived at the airport each was wearing a light blue shirt with epaulettes, and wire-rimmed glasses. They both collected rubber bands, which they wore around their wrists, and washed their hands both before and after using the bathroom. Both liked to startle people by sneezing loudly in elevators.
One pair of MZA women both wet the bed until age 12 or 13. When they were teenagers they started having nightmares about the same things: fishhooks and doorknobs. Both had problems with nightmares for more than ten years.
One pair of MZA men had been overweight until middle school and then became quite thin. They had speech problems for which they received therapy in kindergarten or grade school. Both were diagnosed as hyperactive at about the same age, and both were actively and openly homosexual.
A pair of female MZA twins from Australia found each other because of a case of mistaken identity. They both worked as fashion buyers for competing department stores, and a customer accused one of moonlight for the competition. They were both very elegant, dressed with the same style and the same kind of jewelry, smoked the same cigarettes, and had the same hairstyle, posture, tastes, and speaking voice. One MZA pair of male twins were both fitness fanatics who ran their own body-building gyms. MZA twins generally have the same posture and arrange their hands and legs in the same way while DT twins do not.
Prof. Bouchard, who ran MISTRA, once had occasion to meet a man who had run a smaller-scale MZA study in Denmark in the 1960s, and asked him if he had found such astonishing similarities. The man replied that he had, but he did not report them because was no way to measure such similarities—and he was afraid no one would believe him.
Prof. Segal writes that it was “thrilling” to get to know MZAs and discover how similar they were, but she, too, was frustrated because it was not possible to measure or assess similarities in complex behavior. She notes that when she interviewed MISTRA people to write this book, many looked back with nostalgia on the excitement of their discoveries. One researcher who administered intelligence tests to the twins wished that he had filmed them taking the tests. As he wrote:
I sat quietly behind them. The strategies [for answering test questions] were so different between pairs but within the MZA pairs they were so similar. Both twins vocalized or turned around or stared at the screen or solved the problems quickly. It was amazing. I smiled to myself when I saw these things, thinking no one would believe me.