Bryan Caplan  

Adjective-Coefficient Disconnect in Sacerdote

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I'm now writing chapter 3 of Selfish Reasons to Have More Kids, entitled "Que SerĂ¡, SerĂ¡: The Case for Guilt-Free Parenting."  It's basically a parents' eye guide to behavioral genetics.  As a result, I'm now reading and/or re-reading a bunch of twin and adoption studies.  For the most part, Steven Pinker's summary of this literature is apt:
A handy summary of the three laws [of behavioral genetics] is this: Genes 50 percent, Shared Environment 0 percent, Unique Environment 50 percent (or if you want to be charitable, Genes 40-50 percent, Shared Environment 0-10 percent, Unique Environment 50 percent).
However, some prominent economists working in this area seem to take a very un-Pinkerian position.  The most notable, perhaps, is Bruce Sacerdote, who has done impressive work on Korean adoptees.  His 2007 QJE piece finds "large effects on adoptees' education, income, and health from assignment to parents with more education and from assignment to smaller families."  Indeed, he adds that "One reasonable hypothesis to explain the results in Table VI [which displays his main findings] is that the quantity and quality of parental attention matters a tremendous amount for the adoptees' outcomes."

How can Sacerdote's results be so different from those in mainstream behavioral genetics?  The answer, as far as I can tell, is that the difference is not Sacerdote's coefficients, but the adjectives he uses to describe them. 

What, for example, does Sacerdote count as a "large effect" of parental education and family size on children's educational attainment?  Let's see.  According to his Table VI, every extra year of maternal education raises kids' years of education by .097 years - about a month.  Every additional child in the family reduces kids' years of education by .129 years - about a month and a half. 

What about the probability a kid finishes college?  Every year of maternal education raises it by 2.3%; each kid in the family reduces it by 2.6%.

What about income?  This is an important question to ask - for most economists, the whole point of increasing educational attainment is to increase income!  But Sacerdote finds no statistically significant effect of years of maternal education on income (the point estimate is 0.3%).  The only aspect of family that affects income seems to be the number of kids - each of which reduces it by 4.4%.   If you're finicky, you'll also note that he shows us results for nine independent variables, and only one is statistically significant at the 5% level.

The biggest effect by far in Sacerdote's table: If your mother drinks, you're 18.8 percentage-points more likely to drink.  A big deal?  Not really, since the question asks whether you drink alcohol at all - not whether you drink to excess.

Don't get me wrong.  Sacerdote's work is important and careful.  My objection is merely to his adjective inflation.  Based on my understanding of ordinary English, his effects are not "large," and they certainly aren't consistent with a "tremendous" effect of the quantity and quality of parental attention.

Of course, I won't claim to be the final arbiter of ordinary English.  What do you think?


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COMMENTS (11 to date)
David Friedman writes:

You don't say what Pinker is offering an explanation of. Judith Harris, who reaches a similar conclusion, is pretty explicitly talking about adult personality. Her evidence suggests that it is in part genetics, in part non-family enviroment, but that nurture, how parents bring up their children, has a negligible effect.

That's consistent with Sacerdote's evidence, which deals not with personality but with outcomes. Thus, for instance, parental income could influence the child's income via the parents' ability to send the child to a good college without influencing the child's personality at all. And a child adopted by American parents is going to have different tastes in food than one adopted by Indian or Chinese parents, whether or not there is any difference in personality.

pushmedia1 writes:

I recently saw a lecture where genetic influence was dismissed because the hypothesis of environmental influence wasn't rejected.

I can't put my finger on it, but I suspect there's more to it than just adjective inflation or wishful thinking. There's some logical error being made.

Bryan Caplan writes:

It's true, David, that Harris focuses on personality. But at least one personality trait - Conscientiousness - should definitely affect outcomes. And most of Harris' critique is as relevant for outcomes as it is for personality traits. I suspect she'd endorse the extension. Want me to ask her?

Nigel Kearney writes:

Pardon my ignorance, but what is meant by "Unique Environment" and "Shared Environment" ?

David Friedman writes:

Bryan points out that some personality traits affect outcomes, which is true but irrelevant. The question is whether they are the only thing that affects outcomes. If they are not, then the observation that outcomes are in part determined by parental environment isn't inconsistent with the claim that personality is not determined at all by parental environment.

I would be very surprised if Judith Harris argued that parents had no effect on outcomes. After all, one of the things parents can do is leave lots of money to their children. Another is to refuse to send their children to a doctor when they get sick. And whether your parents can afford to send you to college surely has some effect on whether you go to college.

But you can ask her--or I can. We might not put the question in the same way. Perhaps you should show her our exchange.

Dan Hill writes:

Since we're referring to Korean adoptees, how about the Korean guy who a silver for US in the freestyle skiing at the last winter Olympics. He was adopted at 3 years of age by a pair of ski instructors. How much of his success was genetic and how much environmental?

Troy Camplin writes:

I know you're basing your work on Harris' and Pinker's work, but I don't find her all that convincing precisely because she focuses on "personality." And I'm beginning to wonder a bit on a few of Pinker's ideas. One, there is much more to raising a child than personality development. Consider education. My wife is Hispanic and teaches bilingual Kindergarten. It is common in Hispanic culture for young children to not know words for most objects -- far, far fewer nouns than non-Hispanics -- precisely because Hispanic parents tend to tell their children "Bring me that thing" (In Spanish, of course) rather than use the name of the thing. My wife thus noticed that Hispanic children come in with a severe vocabulary deficit which she has to try to begin to make up. In the meantime, of course, the non-Hispanic children are busy learning many more words they don't know on top of those they already do. Only rarely do the Hispanic children catch up, and then only those with the highest IQs. HOw can one argue, then, that parenting -- and this is an issue of parenting -- doesn't have an effect on the educational outcome of those children? Of course it does. COnsider too McWhorter's opinion piece today where he observes that too many African-AMericans don't help their children with homework. That's going to make a difference. A great example is by brother, who is dyslexic. In a family other than ours, he wouldn't have even gone to college -- but my mother sat for hours a day until she helped him learn how to read. He now has a M.A. and is working on an M.F.A. I, on the other hand, would have managed to succeed in just about any environment -- but I didn't have any learning disabilities, either. My wife too. In fact, she was raised by her grandparents, who thought anything past high school was a waste of time (more, just a way to avoid working). She has a M.A., and would like to get her Ph.D. So it seems to me that if all you're doing is studying people with high I.Q.'s and no learning disabilities, you will get the kinds of result you see from Harris and Pinker. But if not, you won't.

Bryan Caplan writes:
David Friedman writes:

Bryan points out that some personality traits affect outcomes, which is true but irrelevant. The question is whether they are the only thing that affects outcomes. If they are not, then the observation that outcomes are in part determined by parental environment isn't inconsistent with the claim that personality is not determined at all by parental environment.

You're absolutely right, I don't know what I was thinking.
I would be very surprised if Judith Harris argued that parents had no effect on outcomes. After all, one of the things parents can do is leave lots of money to their children. Another is to refuse to send their children to a doctor when they get sick. And whether your parents can afford to send you to college surely has some effect on whether you go to college.
Remember, this is analysis of variance. The fact that extreme parenting would make a huge difference doesn't matter unless extreme parenting actually happens often enough to pick up in the data. If virtually all parents send their kids to doctors when they need them, analysis of variance won't pick up the effect. Similarly, if college-ready kids who don't go because of lack of parental financial support are rare, it won't show up in the data.
But you can ask her--or I can. We might not put the question in the same way. Perhaps you should show her our exchange.
I emailed her, but she hasn't responded. You're welcome to see if your hotline works better than mine. :-)
Troy Camplin writes:

I don't think it even has to be as extreme as Friedman suggests. See my post, above. There's much more to cognitive development than just personality. Personally, Harris never did a good job of explaining what she even meant by personality. I mean, my personality is greatly affected by the things I know and the education I received -- and my parents did influence that in many ways. I think it's pretty hard to differentiate between home and external environment most of the time. If the values my parents instill in me in the home affect the friends I make, and the friends I make affect my personality, then where, ultimately, is the effect?

Jason Malloy writes:

It is common in Hispanic culture for young children to not know words for most objects -- far, far fewer nouns than non-Hispanics -- precisely because Hispanic parents tend to tell their children "Bring me that thing" (In Spanish, of course) rather than use the name of the thing.

What is "Hispanic culture"? Spanish people and European descended Spanish speakers from all over the Caribbean and Latin American exhibit no such language-based deficits. This is a just-so explanation for under-achievement due to IQ.


Only rarely do the Hispanic children catch up, and then only those with the highest IQs.

This isn't correct. IQ is equally predictive for whites and Mexican-Americans.

HOw can one argue, then, that parenting -- and this is an issue of parenting -- doesn't have an effect on the educational outcome of those children? Of course it does.

Because this is what adoption studies show. Once genes are accounted for, family has very little effect on educational outcomes.

A great example is by brother, who is dyslexic. In a family other than ours, he wouldn't have even gone to college -- but my mother sat for hours a day until she helped him learn how to read. He now has a M.A. and is working on an M.F.A.


Troy, this is just one of those things where the data is more reliable than anecdotes. There's plenty of room for bias in your interpretation of events. If your brother really has the motivation to get an M.A., it's extremely probable he would have sought out the help he needed in most alternative environments. In fact, his own personality may have been more instrumental in extracting that help from your mother than her personality was in extending it. Observation doesn't allow you to rewind time, put your brother in another random household and see what happens.

I'm not going to pretend I know anything about your family, I'm just saying that your intuitions here are not supported by a more reliable form of experiment for the broader population.

Troy Camplin writes:

My brother showed much resistance to being helped at all. My mom had more will to help him than he had to making her help him (he would have been much happier playing than in reading "Ten Apples Up On Top" for the hundredth time that month)." The work she did helped to make it possible at all for him to succeed in college -- even if his decision to go to college was influenced by the friends he had (which I have no doubt was the case). I have no doubt I.Q. is inherited and has nothing to do with how a child is raised -- but what that child does with that I.Q. is influenced by a wide variety of things.

I am partially resistant to the research precisely because I don't see any of the kinds of things I point out actually dealt with in the research. Show me the research that deals with how children make friends in school, what their selection criteria are, etc., and then show me that it is completely unrelated to home values instilled by parents.

There are certainly several Hispanic cultures, and I should have been more specific. I cannot speak to other Hispanic cultures, but what I said about the Mexican culture is certainly true. And it is a cultural thing passed on in the home. If you don't know what things are called, how can you talk or think about them? Concept-formation is weakened -- especially those that matter most for living in a human society. You cannot tell me that cognitive delays don't affect I.Q., because we know they do. Many things that go on in the home affect cognitive development, ranging from physical and sexual abuse to affection (lack of affection causes cognitive delays, as we know from Eastern European orphanages) and language use. My mother refused to let my brother and me talk with a southern accent (she was from South Bend, IN, and we grew up in Kentucky) -- can you seriously say that didn't have an effect? The way people express themselves affects the way others treat them. Your initial language patterns are learned in the home -- and different parents intervene at different levels with new language patterns their children learn outside the home. Everyone who met us as children for the first time assumed my brother and I were very intelligent and made good grades precisely because of how well we spoke. Part of that was because we both did in fact have high I.Q.'s -- but part of it was because we didn't make use of "I reckon" and "Y'all."

I've read Harris' book, and I'm not entirely convinced. I think she introduced a healthy corrective and forced people to rethink their assumptions, opening up the possibility for better research -- but I think she went too far, and I don't think she dealt with things in their full complexity. Nor does the research I am familiar with that purports to support her. Like I said, she never sufficiently defined "personality." And while you give I.Q. studies, I never denied those kinds of studies. And I.Q. is not personality (though it certainly can and does affect it).

In the end, there's not a stripper gene, and your friends won't convince you to become one. We know that, though not all sexually abused girls become strippers, almost every stripper was in fact sexually abused in the home. That is the home affecting one's entire life and personality. One cannot create science or theory based on the extremes, but one's science and theories must take the extremes into consideration, or they explain nothing but what you want to see. And at the same time, it's not that much of an extreme. There are an awful lot of strippers out there.

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