So perhaps a clearer three-way partition (assuming that basically all significant environmental influences are themselves influenced by family environment) would be:

1. Heredity

2. Family-influenced environment

3. Random noise

I guess it shouldn't be surprising that there's a fair element of randomness in how we turn out.

Expand full comment

It's worth noting that the brain, being a dynamic, extremely non-linear system, can amplify and retain signals originating even at the level of random quantum events (like electron delocalization affecting a molecule that triggers the firing of a neuron), so we don't have to assume that all the relevant random noise arises from causal factors that are external to the brain.

Expand full comment

This seems like a semantic complaint rather than a substantive one. Harris’s position might be summarized (I’m guessing) as: taking family environment as given, the coefficient on peer effects’ influence on outcome is A; taking peer environment as given, the coefficient of family environment on outcome is B. A >> B.

Even your contention that family environment determines peer group (again, it’s a purely semantic criticism. When people are talking about family environment, choosing where or in what subculture to raise their kids isn’t what they have in mind) can be flipped: your decision to raise your kids in an orthodox Jewish community is determined more by the fact that you grew up around orthodox Jewish peers. Peer effects therefore determine family environment. Thinking about it intergenerationally, it’s arbitrary of course which one is said to cause the other, basically a chicken or egg question. Which is why it’s only meaningful to compare the two in the sense of comparing which has a higher coefficient on outcome controlling for the other one.

Expand full comment

Mainly the "non-shared environment" AKA everything else is: 1) errors and biases in measurements, 2) random biological noise. These E influences are not stable over time and not of much importance. See e.g. https://www.emilkirkegaard.com/p/getting-personality-right and https://www.emilkirkegaard.com/p/heritabilities-are-usually-underestimated Peers and teachers are not important, as shown in school separation twin studies, twins that go to the same classroom are just as similar as those that go to different classrooms or even schools. https://www.emilkirkegaard.com/p/school-factors-are-not-important-evidence-from-classroom-separation-studies

Expand full comment
Apr 8·edited Apr 8

Any imprecisions in the measurement instruments should be a substantial part of NSE. I don’t believe in metaphysical free will, but also believe that behavioral genetics should not diminish one’s belief in personal responsibility. Just use the common sense definition: you have free will if not under gunpoint.

Expand full comment

Maybe not free will so much as in utero effects. Twin births tend to be more difficult than singeltons, and often one twin is disproportionately affected by poor placental performance or more severe issues like ttts. Perhaps we may be overestimating the ransom noise effect given twins are more likely to experience these adverse but random events in utero.

Expand full comment

Interesting post.

Regarding the awesome metaphysical power of free will: Let’s imagine two genetically identical individuals leading parallel lives in identical universes, so that their shared and non-shared environments and experiences are identical in every detail. Despite this, they begin to diverge in their paths. Suppose we attribute this divergence to free will. This Implies, naturally, that their wills differed. The question then arises: where did this difference originate? Random quantum phenomena? The constitution of their souls? As I see it, in this thought experiment it would be impossible for the paths of the two individuals to diverge, unless random quantum phenomena could cause such divergence, but then (libertarian) free will would have nothing to do with it.

Expand full comment

Concerning peer groups and their importance:

1. Peer groups probably are partly determined by the family environment, yet doesn’t experience also tell us, that we find friends who might be more or less accepted or aligned with our family environment, the wishes and ways of our family? Why do we prefer some friends over others - I’d say it’s hugely determined by our genes, by the emotions awakened through the interactions with them. Why is Robin Brian’s best friend?

2. Peer groups can’t completely be a product of the family environment, since we are not free to choose our peer groups. We might wish to join a peer group, but might not be accepted. Maybe because we weren’t funny, clever or beautiful enough, maybe the opposite. Thus - who chooses us, affects who we can be. Why do we get accepted or rejected by a peer group - I believe their is a lot of randomness and serendipity in that, but also the simple fact that we are, who we are, because of our genes. Again - your peer group is also decided to a large extent by your genes.

Expand full comment

"If heredity fully explains trait A, which interacts with a complex environment to produce trait B, the math says that heredity fully explains trait B as well."

This is not even close to true. You should reconsider your just so stories. Yes, super beautiful people are treated differently and that affects them. So what's 100% hereditary (in this 100% hereditary beauty world) is some vague catch all "effects of differences in treatment due to beauty". What those are will vary by...the interaction with a complex environment. IOW, they are not 100% hereditary.

Expand full comment

Well . . .

The variation of human life only adds to 1 if there is no free-will.

Free will has no cause other than will of the person.

Of course, most don’t use much of their free , uncaused choice.

That doesn’t prove free will doesn’t exist.

Einstein never accepted bohr’s quantum physics.

Same data, different choice.



Expand full comment

Thanks, Parent of a 14-month-old. Great food for thought.

Expand full comment

Harris was inspired to conclude that peer effects are more important than "nurture" by observing that immigrants retain their accents if they immigrate as adults, but wind up with the accent of their host country if they immigrate when young. In contrast, "the metaphysical power of free-will" makes no useful predictions.

Expand full comment

The trouble with that example is that we know language development changes with age, even so far as you stop being able to differentiate between certain sounds if you don’t hear them when young. It seems perfectly reasonable (though I don’t know if it is true) that changing your accent when young is very easy, even hard to avoid, whereas by the time you are in your 20’s say it becomes very difficult, requiring a lot of conscious effort, or might be impossible for most people.

Expand full comment

In terms of of your own parenting, how important are your children’s peers? What actions do you actually take in your own life?

Expand full comment

A better question would be how much direct influence does one have over their kid’s peers and selected friend group. I recall my sister dating a few guys my parents were not too happy about, and on the other side of the coin although we have introduced my daughter to a number of really nice and smart kids her age when she started her new school she only cleaved to a small number of them. Which suggests to me that peer group selection is driven as much by who your kid is inclined to like than the peer group affects them. Parents don’t have fine control over peer groups sufficient to really affect kids enough for it to show up.

Expand full comment

It really depends on the situation and financial means of the family. Some families can move to new schools that are very different from public schools. They can move to different cities and states. Different cultures. Rural, conservative, libertarian places. Outdoor places. And parents can make choices to be good role models, change their own behavior, not fund certain activities for their kids, restrict social media and cell phone, require kids participate in family activities, eliminate the possibility for certain peers to interact with their kids. It really depends on the family’s situation and creativity.

Expand full comment

It also depends on the available peers to choose from, too. Parents exercise negative influence (moving away from a bad school) but are more limited in positive influence of peer group because it depends heavily on what other kids are around. You can move to a good school, but if your kids class happens to be crappy, or your kids cleave to bums, there isn’t really a lot you can do.

And more on point, that should all correlate heavily with shared home environment if parents can control it, as the parents are affecting it. So if they can affect it (and they can to an extent) it should show up in shared home environment. If they can’t affect it it should be no shared home. Neither seems to be affecting outcomes, even with “peers plus everything else” rolled in.

Expand full comment

I mean, at the limits, the amount of control you have over your kids' peer groups is HUGE.

You can cut them off entirely from peers their age via homeschooling (and this led to JS Mill being a child prodigy, because his "peer" group were the savants and intellectuals of his parent's social circle). You could decide to raise them in NYC instead of Mississippi, you can send them to Boarding School with other rich kids, you can raise them in a tightly-knit religious community where all thier "peers" are other religious kids, you could raise them with you as their only peers as you live an itinerant life on a boat or RV, you can live in an isolated off-grid homestead in a nature reserve, and a hundred other things.

Parents basically entirely control kids' external environment, and if it's something they want to change a lot or optimize on, there's actually quite a lot they can do. Some of the moves require money or a good deal of commitment and change on the parent's part, sure. But you have almost absolute control over the environment your kids grow up in if you really put your will into it.

Expand full comment

"Parents basically entirely control kids' external environment"

So... you are saying the peer group is the same as the shared home environment, at the limit?

Away from the limit, somewhere in the range of what "normal" people do, there isn't a ton of control over peer group because while you can pick the area you live in, the school they go to (or home school) etc. you are limited by who your kids will decide to hang out with (which is partly determined by genetics given a set of peers) and what other parents decide to do. You can't will a set of high quality peers into existence, only the kids that happen to have come out of the loins of local parents. Even your tight knight religious community only has the kids those other parents had, for good or ill.

So yea, you can spend massive amounts of resources to micro manage your kids' out of the home experience, and get a fair amount of control. Not "basically entirely control" by any stretch seeing as how you can't generally dictate what other kids will be around, or what other humans in general will be like, but you have some control. That control shows up in shared home environment, I believe is Bryan's point, however, because once you have bought your home and your school and started going to work again, your kids' external environment is dependent on that; you've chosen the external environment and now they are moving within it making their decisions on who to hang out with and who not. The peer group is highly correlated to home environment.

But unless you are really inclined to micromanage your kids' social lives, to the point of hiring friends maybe, there isn't a lot you can do with peers. Once it involves other people outside the family you have limited control.

Expand full comment

Yeah, I think we're agreeing with each other, and just quibbling a little over edge cases.

> you are limited by who your kids will decide to hang out with (which is partly determined by genetics given a set of peers) and what other parents decide to do. You can't will a set of high quality peers into existence

Yeah, but my point was, you can surely limit the downsides. It's playing the odds, right? A rich and religioius community is going to have a lot fewer malcontents and layabouts, and thus your odds are better for your kids peering in that population.

Sure, it involves other people outside your family, but that pool isn't random, it's selected, and you can select it in better directions, and play the odds for your kids to have better peers.

Expand full comment

Actually, let me be more clear, I think I am writing a bit too loosely so we are talking past each other.

If peer group has a large effect, like larger than genetics, it has to be pretty visible, so either shared home environment or non-shared has to be big, or if it is correlated with shared home environment it might be spread between shared and non-shared because you have basically the same variable in two places in the equation so the coefficient will be misleading.

Bryan is arguing (and I tend to agree) that shared home environment largely determines peer group, because of where you live, where your parents spend money to send you to school, what church they pick etc. is all the same for their kids, so the weight should fall there if peer group matters a lot. Shared home environment doesn't seem to matter a lot (within normal bounds) compared to genetics, so peer group probably doesn't either. Home environment directly or indirectly picks peer group, and home environment doesn't count for much.

I would differ a bit in that I would say genetics will tend to indirectly affect peer group a good bit (smart kids tend to hang out together, sporty kids, etc.) and within the normal range of "I send my kid to the local school" most parents don't have control. So I would say peer group is correlated with all three categories, and almost would have to be specifically controlled for by individuals to tease out. My guess, however, is that holding the shared home environment fixed, peer group is driven as much by genetics as much as a separate thing.

So to reiterate, peer group is largely an indirect effect of shared home environment, and I think a bit more of an indirect effect of genetics, than just being totally in non-shared home environment.

Expand full comment