good coaching, in part from hanging around the national and Olympic coaches he was studying?
“Years later, I got back into the pool, got in shape again, and swam a two-hundred-yard individual medley as fast as I did in high school.”
Again, same story. Not just nature, and not just nurture. Both.
----
How do scientists know, with unwavering conviction, that both nature and nurture play a role in determining things like talent and grit? Over the past few decades, researchers have been studying identical and fraternal twins, raised in the same family or raised in different families. Identical twins have all the same DNA, while fraternal twins, on average, only share about half. That fact, and a whole lot of fancy statistics(well, not that fancy—more mundane, really, once a good teacher explains them to you), allows researchers to infer, from how similar the twins grow up to be, the heritability of a trait.
Very recently,researchers in London let me know they’d administered the Grit Scale to more than two thousand pairs of teenage twins living in the United Kingdom. This study estimated the heritability of the perseverance subscale to be 37 percent and the passion subscale to be 20 percent. These estimates are on par for heritability estimates for other personality traits, and in the simplest terms, this means that some of the variation in grit in the population can be attributed to genetic factors, and the rest can be attributed to experience.
I hasten to add that there isn’t just one gene that explains the heritability of grit. On the contrary, dozens of research studies have shown that almost all humantraits are polygenic, meaning that traits are influenced by more than one gene. Many more, in fact. Height, for example, is influenced by, at last count,at least 697 different genes. And some of the genes that influence height influence other traits as well. In total, the human genome containsas many as twenty-five thousand different genes, and they tend to interact with one another and with environmental influences in complicated, still poorly understood, ways.
In sum, what have we learned? First: grit, talent, and all other psychological traits relevant to success in life are influenced by genes and also by experience. Second: there’s no single gene for grit, or indeed any other psychological trait.
----
I’d like to make a third, important point: heritability estimates explain why people differ from the average, but they say nothing about the average itself.
While the heritability of height says something about variability—why in a given population some people are taller and some shorter—itsays nothing about how average height has changed. This is important because it provides evidence that the environment we grow up in really does matter, and it matters a lot.
Here’s another striking example, and one more relevant to the science of success: the Flynn effect. Named after Jim Flynn, the New Zealand social scientist who discovered it, the Flynn effect refers to startling gains in IQ scores over the past century. How big are the gains? On the most widely used IQ tests today—the Wechsler Intelligence Scale for Children and theWechsler Adult Intelligence Scale—gains have averaged more than fifteen pointsin the last fifty years in the more than thirty countries that have been studied. Put another way, if you scored people a century ago against modern norms, they would have an average IQ score of 70—borderline for mentally retarded. If you scored people today against the norms of a century ago, we would have an average IQ score of 130—the typical cut score for mentally gifted programs.
When I first learned about the Flynn effect, I didn’t believe it. How could it be that we’re all getting that much smarter so quickly?
I called Jim to share my incredulity—and my desire to learn more—and, globe-trotter that he is, he actually flew all the way to Philadelphia to meet with me and give a talk
“Years later, I got back into the pool, got in shape again, and swam a two-hundred-yard individual medley as fast as I did in high school.”
Again, same story. Not just nature, and not just nurture. Both.
----
How do scientists know, with unwavering conviction, that both nature and nurture play a role in determining things like talent and grit? Over the past few decades, researchers have been studying identical and fraternal twins, raised in the same family or raised in different families. Identical twins have all the same DNA, while fraternal twins, on average, only share about half. That fact, and a whole lot of fancy statistics(well, not that fancy—more mundane, really, once a good teacher explains them to you), allows researchers to infer, from how similar the twins grow up to be, the heritability of a trait.
Very recently,researchers in London let me know they’d administered the Grit Scale to more than two thousand pairs of teenage twins living in the United Kingdom. This study estimated the heritability of the perseverance subscale to be 37 percent and the passion subscale to be 20 percent. These estimates are on par for heritability estimates for other personality traits, and in the simplest terms, this means that some of the variation in grit in the population can be attributed to genetic factors, and the rest can be attributed to experience.
I hasten to add that there isn’t just one gene that explains the heritability of grit. On the contrary, dozens of research studies have shown that almost all humantraits are polygenic, meaning that traits are influenced by more than one gene. Many more, in fact. Height, for example, is influenced by, at last count,at least 697 different genes. And some of the genes that influence height influence other traits as well. In total, the human genome containsas many as twenty-five thousand different genes, and they tend to interact with one another and with environmental influences in complicated, still poorly understood, ways.
In sum, what have we learned? First: grit, talent, and all other psychological traits relevant to success in life are influenced by genes and also by experience. Second: there’s no single gene for grit, or indeed any other psychological trait.
----
I’d like to make a third, important point: heritability estimates explain why people differ from the average, but they say nothing about the average itself.
While the heritability of height says something about variability—why in a given population some people are taller and some shorter—itsays nothing about how average height has changed. This is important because it provides evidence that the environment we grow up in really does matter, and it matters a lot.
Here’s another striking example, and one more relevant to the science of success: the Flynn effect. Named after Jim Flynn, the New Zealand social scientist who discovered it, the Flynn effect refers to startling gains in IQ scores over the past century. How big are the gains? On the most widely used IQ tests today—the Wechsler Intelligence Scale for Children and theWechsler Adult Intelligence Scale—gains have averaged more than fifteen pointsin the last fifty years in the more than thirty countries that have been studied. Put another way, if you scored people a century ago against modern norms, they would have an average IQ score of 70—borderline for mentally retarded. If you scored people today against the norms of a century ago, we would have an average IQ score of 130—the typical cut score for mentally gifted programs.
When I first learned about the Flynn effect, I didn’t believe it. How could it be that we’re all getting that much smarter so quickly?
I called Jim to share my incredulity—and my desire to learn more—and, globe-trotter that he is, he actually flew all the way to Philadelphia to meet with me and give a talk
Similar Books
