From the Wall Street Journal:
If you harbor any curiosity about why people turn out the way they do, Ms. Segal's topic will fascinate. How big are the effects of nature, nurture and everything else? Despite ample jargon and abstruse statistics, the logic of the Minnesota study is simple. When identical twins are raised apart, you can disentangle nature and nurture for a given characteristic by simply measuring how similar the twins are. You can double-check your answer by comparing the similarity of identical twins (who share all their genes) and of fraternal twins (who share only half their genes).
The Minnesota researchers tracked down every pair they could find—and measured traits related to almost every aspect of life: health, cognition, personality, happiness, career, creativity, politics, religion, sex and much more. The Minnesota study reveals genetic effects on virtually every trait. The breakdown between nature, nurture and everything else varies from trait to trait. But Ms. Segal emphasizes the uniformity of the results—the consistent power of genes, the limited influence of parenting.
---"O Brother, Where Art Thou? (How genetic is that distinctive chuckle or curious disposition? Twins raised in separate homes offer a ready-made experiment.)" by Bryan Caplan, Wall Street Journal (6.20.2012)
It's mostly about our genetics. It is, whether we like that answer or not.
The article quoted is a review of a new book, Born Together—Reared Apart, by Nancy L. Segal, "a thorough history of the Minnesota study and the 137 pairs of star-crossed twins who made it possible." Ms. Segal was a key member of the Minnesota research team.
Twin studies are not new. And the Minnesota study results have been around more than two decades. Even when I was an undergraduate, there was evidence and discussion about identitical twin studies and the implication of a greater influence by our individual genetic profile. Predictably, I suppose, the foundational interests of my undergraduate career were formed around a major in psychology (with a focus on operant and classical conditioning) and a minor in biology (with a focus on genetics).
For me, it's been a life long interest and quest to better understand identity, the things that make us who we are. And that comes down to the questions of "nature vs. nurture," how much of who we are is a function of our genetic endowment, and how much is a function of our family and cultural conditioning, our learning and experience. And for me, at least, I must add matters of spirituality and faith to nature and nurture in that quest for understanding identity. (And interestingly, studies of the genome have also found aspects of spirituality or faith to be influenced by our genes.)
Lets take a quick look at some of the more detailed findings and issues growing out of the Minnesota study:
The article quoted is a review of a new book, Born Together—Reared Apart, by Nancy L. Segal, "a thorough history of the Minnesota study and the 137 pairs of star-crossed twins who made it possible." Ms. Segal was a key member of the Minnesota research team.
Twin studies are not new. And the Minnesota study results have been around more than two decades. Even when I was an undergraduate, there was evidence and discussion about identitical twin studies and the implication of a greater influence by our individual genetic profile. Predictably, I suppose, the foundational interests of my undergraduate career were formed around a major in psychology (with a focus on operant and classical conditioning) and a minor in biology (with a focus on genetics).
For me, it's been a life long interest and quest to better understand identity, the things that make us who we are. And that comes down to the questions of "nature vs. nurture," how much of who we are is a function of our genetic endowment, and how much is a function of our family and cultural conditioning, our learning and experience. And for me, at least, I must add matters of spirituality and faith to nature and nurture in that quest for understanding identity. (And interestingly, studies of the genome have also found aspects of spirituality or faith to be influenced by our genes.)
Lets take a quick look at some of the more detailed findings and issues growing out of the Minnesota study:
Some findings go down easy: As most would expect, identical twins raised apart have virtually identical heights as adults. Some findings seem obvious after the fact: Genes, but not upbringing, have a pretty big effect on personality traits like ambition, optimism, aggression and traditionalism. Other findings perennially cause outrage: The IQs of separated identical twins are almost as similar as their heights. Critics of intelligence research often hail the importance of practice rather than inborn talent, but a three-day test of the Minnesota twins' motor skills showed that how much you benefit from practice is itself partly an inborn talent.
The Minnesota study's IQ results hit a nerve years before their publication in 1990, overshadowing other controversies that might have been. Many of its findings are bipartisan shockers. Take religion, which almost everyone attributes to "socialization." Separated-twin data show that religiosity has a strong genetic component, especially in the long run: "Parents had less influence than they thought over their children's religious activities and interests as they approached adolescence and adulthood." The key caveat: While genes have a big effect on how religious you are, upbringing has a big effect on the brand of religion you accept. Identical separated sisters Debbie and Sharon "both liked the rituals and formality of religious services and holidays," even though Debbie was a Jew and Sharon was a Christian.
Nonetheless, I've always been inclined to be respectful of the power of the family and culture to shape our behavior as well. And about seven years ago, I wrote about the determinism of both nature and nuture, and the quest to find something like freedom and choice in directing or shaping--redirecting or reshaping--our lives or some behaviors, at least, if not our identity. (This link will take you to that essay titled, "Choices.")
But research like this reported in the Minnesota study suggests that the role of nurture, the power of our surroundings, are more limited, shaping our behavior more at the margins or possibly only for a time. Another study I reported not long ago found more specifically that the role of parents in shaping their children's personality or behavior is limited. It found that within about five years of being fully independent of their parents, children move more toward the people, traits and behaviors that their genetic endowment dictates or predisposes them toward. (So, don't be so hard on yourself, Mom and Dad!)
There are exceptions, of course. Particularly dramatic experiences--and especially longer-term abusive situations--can have enduring effects on an individual's personality, temperament or behavior. Then there are the so-called "orchid children" whose personalities and temperaments are so fragile that a negative (but not necessarily abusive) family situation can result in disfunctional individuals, whereas a particularly supportive and affirming family situation can reveal an extraordinarily talented and well-adjust individual. But for most of us, it appears, the philosophy or approach of our parents in rearing us does not dictate who we are likely to become nearly as much as we thought.
It's worth reading the rest of the article if the topic interests you, and maybe even the book:
But research like this reported in the Minnesota study suggests that the role of nurture, the power of our surroundings, are more limited, shaping our behavior more at the margins or possibly only for a time. Another study I reported not long ago found more specifically that the role of parents in shaping their children's personality or behavior is limited. It found that within about five years of being fully independent of their parents, children move more toward the people, traits and behaviors that their genetic endowment dictates or predisposes them toward. (So, don't be so hard on yourself, Mom and Dad!)
There are exceptions, of course. Particularly dramatic experiences--and especially longer-term abusive situations--can have enduring effects on an individual's personality, temperament or behavior. Then there are the so-called "orchid children" whose personalities and temperaments are so fragile that a negative (but not necessarily abusive) family situation can result in disfunctional individuals, whereas a particularly supportive and affirming family situation can reveal an extraordinarily talented and well-adjust individual. But for most of us, it appears, the philosophy or approach of our parents in rearing us does not dictate who we are likely to become nearly as much as we thought.
It's worth reading the rest of the article if the topic interests you, and maybe even the book:
Mr. Caplan, a professor of economics at George Mason University, is the author of "Selfish Reasons to Have More Kids: Why Being a Great Parent Is Less Work and More Fun Than You Think."
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