What Do You Think?
Name:
Bouchard discovered the "Jim Twins," Jim Springer and Jim Lewis, who were separated at birth and reunited in
1979 at age 39. Born in 1940, Jim Springer and Jim Lewis were adopted by different families.
In 1979, psychologist Thomas Bouchard, interested in the nature/nurture debate, began a detailed
investigation of identical twins who were separated at birth. The Jim twins caused a public stir early in this
study, as they shared remarkably similar lives.
Aside from the fact that they were both named Jim by their adoptive parents, the twins had both married
twice - the first time to women named Linda and the second to women called Betty. Jim Springer named his son
James Allen and Jim Lewis called his son James Alan. They both had dogs named Toy, both spent time as
sheriff's deputies, they drank the same beer (Miller Lite), smoked the same cigarettes (Salem) and drove the
same model of car (light blue Chevrolet). Both Jims took family Florida vacations in Pass-a-Grille. Both left
love notes to their wives around the house.
These statistics have shown that on average, identical twins tend to be around 80 percent the same in
everything from stature to health to IQ to political views. The similarities are partly the product of similar
upbringing. But evidence from the comparison of twins raised apart points rather convincingly to genes as the
source of a lot of that likeness. In the most widely publicized study of this type, launched in 1979, University of
Minnesota psychologist Thomas Bouchard and his colleagues have chronicled the fates of about 60 pairs of
identical twins raised separately. Some of the pairs had scarcely met before Bouchard contacted them, and yet
the behaviors and personalities and social attitudes they displayed in lengthy batteries of tests were often
remarkably alike.
The first pair Bouchard met, James Arthur Springer and James Edward Lewis, had just been reunited at
age 39 after being given up by their mother and separately adopted as 1-month-olds. Springer and Lewis, both
Ohioans, found they had each married and divorced a woman named Linda and remarried a Betty. They shared
interests in mechanical drawing and carpentry; their favorite school subject had been math, their least favorite,
spelling. They smoked and drank the same amount and got headaches at the same time of day.
Equally astounding was another set of twins, Oskar Stohr and Jack Yufe. At first, they appeared to be a
textbook case of the primacy of culture in forming individuals -- just the opposite of the Lewis-Springer pair.
Separated from his twin six months after their birth in Trinidad, Oskar was brought up Catholic in Germany and
joined the Hitler Youth. Jack stayed behind in the Caribbean, was raised a Jew and lived for a time in Israel. Yet
despite the stark contrast of their lives, when the twins were reunited in their fifth decade they had similar
speech and thought patterns, similar gaits, a taste for spicy foods and common peculiarities such as flushing the
toilet before they used it.
Bouchard's collection of twins-raised-apart is unique in American behavior genetics. In most twin
studies, including Eaves's research, scientists are comparing the similarities between identical twins and
fraternal twins; in other words, they compare comparisons. To test the assumption that genes play a role in IQ,
for example, scientists ask whether the IQs of identical twins (who share all their genes) are more similar than
those of fraternal twins (who share an average of 50 percent). To have any statistical validity, such studies must
examine thousands of twin pairs. But enough studies have been done to show that identical twins are roughly 85
percent similar for IQ, fraternal twins about 60 percent. Crunching the numbers, behavior geneticists say about
half the variation in IQ, whether among twins or non-twins, may be due to genes.
It was this figure that provided the grist for the controversial 1994 book The Bell Curve, whose
conservative authors argued that little could be done to help the poor because they suffered from low IQs that
were fixed, for the most part, by their genes. The book has been disputed by many critics, including those who
deny that IQ is a worthy measure of intelligence. Even if it is, though, the genetic component of IQ that The
Bell Curve trumpets is not an overwhelming factor: Even if half of IQ variation is due to genes, that leaves
room for plenty of average kids to be born to brilliant parents, and vice versa. And when children of smart
parents are smart, it is nearly impossible to know whether this is due to the "smart" genes they inherited, or the
"smart" environment their parents provided.
When journalists first began interviewing Bouchard's twins-raised-apart, they focused on the spectacularly
similar pairs, like the Springer-Lewis twins. But those twins turned out to be outliers in the Minnesota study.
Most of the other twins weren't nearly as alike. Furthermore, since no one is claiming there is a gene for
flushing the toilet before you use it, or a gene for marrying women named Betty, such coincidences are
statistical anomalies, as Bouchard is quick to acknowledge
After reading the article, complete the following:
Hypothesis:
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Sample size: ________________________________________________________________________
Summary of findings:
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What do you think the data say about nature versus nurture?
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What are 2 things the “Jim twins” have in common?
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What is the difference between identical and fraternal twins, in terms of their IQ?
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What conclusions does the study draw about nature versus nurture?
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1. Are your personality traits similar to those of your parents? Make a list of the traits you share with your
mother and those you share with your father.
Similar to my mother
Similar to my father
2. Do you sometimes think you “can’t help” the way you respond to situations? For example, do you find
yourself always wanting to be on time? Is this behavior like one of your parents? Do you see “nature” winning
out in this case? Can you think of other examples? Can you think of situations in which "nurture" seems to win
out?
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3. Do your friends influence your behavior? If so, how? Try to be as specific as you can.
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4. Are you influenced by what you see and hear in the media? Describe the impact this has on you.
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5. Are you influenced by other adults in your life, such as a relative, a teacher, or a youth group leader? How
has this person helped shape your personality?
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6. Why do you think nature vs nurture is debated? Is it possible to answer this question definitively? Why?
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7. If you were raising identical twins, what might you do to make sure that they were unique individuals?
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8. Do you think it is possible to change your personality? Why or why not? If so, how would you go about
making changes?
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