Response to Alex on parenting and religion, and a bunch of other points on twin studies

Alex is right on one point, that Bryan's book is very important and everyone should read it.  Otherwise, his discusson of Yana indicates that both genes and upbringing matter, which is my point — that both matter.  He mistakenly cites that example against me, rather than against Bryan, who claimed upbringing and inculcation do not matter for language. 

Orthodox Jews are clearly a case where parenting matters for the religion and religiosity of the kids, not just the abstract fact of having the parent or the possible genetic transmission of general religious fervor.  Orthodox Jewish parents are effective, in part, because they inculcate the religion in their children.  Or look at the data on Korean Protestants.  I could spend a whole day finding credible studies on this question and they are not restricted to a few extreme points (though they also don't cover everyone, and probably strict inculcation of Unitarianism won't work).  There is overwhelming evidence that parenting often does transmit religious observance and if twin adoption studies do not show that it is a sign of their limitations.

In the comments, Cournot (not Augustin) nails it:

Tyler is not rejecting the studies. He's rejecting Caplan's interpretation.

Imagine this were a drug and the trials showed that the drug clearly reduced fever in a stat sig group.

However a number of non-statistically significant side effects were observed. Some patients died, got rashes, or became crippled. We also have anecdotal evidence and even some good theory that there may be weird interactions with some subpopulations, but to date no good studies showing these effects have been conducted.

Should I assume that it's safe to take these drugs? I think not.

Indeed, doctors often warn us of side effects even though most of the side effects don't show up as statistically significant in clinical trials.

Tyler is just saying some of the side effects of parenting on kids may well be significant and until clearly proven otherwise, it is unsound to ignore non-statistical anecdotal evidence [TC: there is plenty of statistical evidence also] just because the major studies don't show any effects.

And here is Richard A.:

The Body-Mass Index of Twins Who Have Been Reared Apart

We conclude that genetic influences on body-mass index are substantial, whereas the childhood environment has little or no influence. These findings corroborate and extend the results of earlier studies of twins and adoptees. (N Engl J Med 1990; 322:1483–7.)

IOWs, the reason why white kids of today are much fatter than white kids of the 50s and 60s is due to genetic influences and environment has little or no influence

This shows that the twin studies are flawed.

If that doesn't convince you, ponder the Zoroastrians, an extreme minority in most of the places they have lived.  Parents inculcated religious observance for centuries, yet now that pattern of replication seems to be falling apart and the religion and way of life is in danger.  In other words, now we are viewing the time series evidence (as does Richard A. in the case of body weight).  Parental inculcation can matter a lot, or not so much at all, depending on circumstances.  The very size of that variation suggests two points: a) cross-sectional evidence alone won't pin down the proper genetic component, for instance studying this group today, rather than across time, would overestimate the genetic influence, and b) if the transmissibility can change so quickly we are pushed away from genetic explanations, though of course without abandoning them altogether.  Genes are still very, very important.

In contrast, what do you expect for the heritability of IQ over the generations?  Lead poisoning and the like aside, I expect estimates of that heritability don't change much over time at all.  That is more closely tied to genetics, and the time series evidence confirms it.


Per Harris, these effects may be coming from the kids' peers. Kids of jewish orthodox parents are around other kids of orthodox parents, and to fit in with and raise their status among such peers, they act orthodox. The kids play along but just because they want to see and fit in with their friends.

My take away form Harris is that new languages are invented by kids of different parental languages being mashed together and inventing a new creole so they can communicate with their peers. Languages must die, then, when it is useless to kids to learn. Must be the same for other customs.

Yes, parents can force you into a peer group to some extent, but if that is what 'parenting' amounts to, it isn't amounting to much.

Cycling back, Harris is saying, kids don't give a damn about impressing their parents compared to impressing their peers. Sometimes what impresses the parents is what impresses the peers, but that only makes it seem like the effects are coming from the parents.

The Richard A study is quite possibly capturing indirect genetic effects. To take a simpler case, imagine two identical twins separated at birth. They both, for genetic reasons, are quite tall for their age as children. So they do a bit better than the other kids at basketball. Finding that they enjoy basketball because they score points a lot, they practice shooting hoops a lot. So they get picked for the school team, so they get more practice and more training, so by the time they're adults they're both very good at basketball. Their genes influenced the environment they lived in to create an indirect effect of genes. Twin studies AFAIK can't identify the difference between direct genetic effects and indirect ones, what they can do is identify the difference between what genes influence and what parents influence.

Parental influence on the composition of a child's peer group is extremely important and difficult. Even if we suppose this is the primary contribution of a parent it is still highly significant.

But in any case there seems to be good anectodal evidence at least that character building (through shaming, for instance), has real world effects. Caplan seems to have no concept of what character and virtue is. For him the fact that studies show that television watching shows no detrimental effects to IQ is sufficient reason to recommend it as a babysitter to be used liberally. Foolish.

So, as a parent, what do you do if you don't want your kids to be fat?

You can cut the TV and Internet cable, you can try to get them to go out for the cross-country team, you can buy untasty and inconvenient foods.

However, probably the most likely changes to succeed involving getting them into peer groups highly biased against fat people. Sell your house in the Rio Grande Valley and move to Manhattan Beach. Send them to an expensive private school where most of the kids are the offspring of highly energetic Type A personalities.

Of course, these can be extremely expensive propositions.

It mystifies me that Tyler continues to cite studies (such as the Korean study that he links to) that simply as a matter of logic cannot shed light on the fundamental question we are debating.

Well, if your point is that both upbringing and genes matter, odds are you're not actually debating anyone...

I think that Tracy raises an interesting point about how substantial parental contributions might be invisible in these twin studies. Suppose that someone with a talent T (say it's genetic) needs a parenting input P in order to develop an ability A. P might in fact be quite onerous, but it might also be one of those onerous things that parents just naturally do when their kids have T. If so, then the data will show an overwhelming relationship between T and A, and the contribution of the onerous (but common) P will be completely invisible to twin studies. (It will simply look like T alone caused A.)

Steve, they agree with you on the heritability of IQ yet they disagree that this has significant implications about immigration policy. Why not take that as an intellectually honest disagreement as opposed to constantly insinuating that it must be because of politically correct pressures?

Perhaps most immigrants from south of here are destined to be less productive than those here. Does that mean they will be unproductive? If they were unproductive I suspect they wouldn't have jobs.

You present immigration as if it were a zero sum game, and then point to the costs of immigration while ignoring even the possibility that the benefits may outweigh the costs.

Is it so hard to believe that when someone voluntarily hires a worker to do a job that the worker voluntarily agrees to do, the odds are value is created?

Tyler's arguments seem irrelevant. His "overwhelming evidence" is in fact not evidence at all, as it does not control for genetic factors. The changing rate of obesity over time is obviously due to environmental factors other than parenting, as shown by the study. No doubt is cast on that. If you are going to write a post this long, try to have at least some modicum of substance?

Cyrus nails it. Alex implies the idea (but won't actually state it, perhaps because it will sound absurd?) that if not for the pushy Korean Protestant parents, roughly a similar number of those children would have gone on to choose a demanding religion. Jaw hits floor. For one thing, how many other similarly demanding religions are there in Korea in any real popularity? Are we really to believe a similar number of those children would have found, on their own, a comparable religious substitute? Would they all have found their way to Korean Protestantism? The implicit hypotheses here virtually defy belief.

Like many other commenters, I think Tyler is trying to attribute peer effects (which everyone acknowledges) to parents. In case you didn't know, Orthodox Jews are very keen on forming communities in which to raise their children.

Cyrus, even if "Protestantism" did not exist, the ancestors of Korean-Protestants did. One of the major points of David Hackett Fischer's "Albion's Seed" is that the regional differences in America associated with religion predated them in England and often reflected the territories in which there was Danish/Swedish settlement.

"Since everybody from Judith Rich Harris to Stephen Jay Gould believes that peer groups matter..."

I don't agree with this. The evidence shows that parents have even more influence than peers. But that ain't sayin' much.

"If Bryan is right and it's all in the genes -- which I think he exaggerates, but is clearly true to some extent -- why do we want to let tens of millions of people from lineages that have never shown much evidence of educational excellence"

Dr. Caplan does not say "it's all in the genes", he says that it's all in the genes and non-shared environment, which is not the same thing. He has also made it clear that his support for open borders is for the immigrants well-being and not the well-being of Americans.

David - entirely so. For a start, someone needs to do a parenting role to keep small children adequately supplied with food and water, if they are to survive at all. But virtually every parent does that naturally if they possibly can, for the obvious reason that we are only descended from those who survived to sexual maturity.
But the questions people typically are interested in are not things that virtually every parent does, it's the things that are different. It's one thing to blame a parent if they, despite having perfectly adequate food supplies, have a child suffering from malnutrition because they didn't feed their child properly, it's another thing to blame a parent on the basis that if they'd hugged their children more often as small the kids would have finished high school/not gotten a criminal record/etc. That's the range of debate.

"I hate the way academics talk about one another. A comment mostly directed to the other contributor to this good blog."

The 'way' Tyler talks about others can be much more devastating than the way Alex does it. That is why he should be, and is more careful. He's getting close to being a little careless here.

Try as you might, you could never produce a chimpanzee from two humans by normal means. However, it would probably be easy to parent up a child to act like a chimp. In that way, genetics has very little 'effect.'

I would be highly skeptical of claims of "religousity", especially in studies that don't target that specifically. Religous observance is notoriously difficult to measure, mostly because in surveys people routinely overstate religous observance. For instance, I've seen studies suggesting monthly church attendence in America is around 40%, while other studies suggest that it is around 20%, while still others suggest it is even lower. This also begs the question: is church attendence really a good measure of religiousity, especially in regards to transmitting it to children? If it's only habitual and not internalized, if observance is only an hour a week, or if instruction does not accompany it, then is it realistic to assume that the person is truly "religous"? Anyone who has been inside the church for any period of time knows that a substantial proportion of those in church are at best nominal in their beliefs.


"Alex implies the idea (but won't actually state it, perhaps because it will sound absurd?) that if not for the pushy Korean Protestant parents, roughly a similar number of those children would have gone on to choose a demanding religion. Jaw hits floor."

No, that seems to be your own argument, not Alex's. You are saying parenting is an important factor in determining religion in determining therefore if parenting is taken out, we should see much higher variance in religious outcomes. Maybe you are not being clear in arguments and everyone actually agrees?

"For one thing, how many other similarly demanding religions are there in Korea in any real popularity?"

Exactly. But, that's an environmental factor, not a parenting factor. Perhaps that's your real argument, that environment matters? Bryan's argument isn't against that however, just that parenting is a much much smaller part of environment that we think. You seem to be giving good anecdotal evidence of that.

I think any argument about the impact of parenting has to be something like a combination of, "We just haven't found the right parenting technique yet" and "obviously, societies are made up of a lot of parents, therefore parents contribute to most/all societal effects, so the effects are just much more diffuse than we think". Both of these arguments however, still agree with some of Bryan's basic arguments that one should not spend too much effort in reading and applying parenting techniques if your goal is improvement of your child.

"However, it would probably be easy to parent up a child to act like a chimp."
There were some researchers who raised their son Donald with a chimp named Gua ("more fun than a barrel-full of Donalds"), which he took to imitating. But despite his see-monkey-bite-wall do-bite-wall behavior, Donald grew up to be a doctor.

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