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I just recently ran into someone posting this on Twitter and it blew my mind:
An intriguing feature of twin studies: anything a parent does to individualize for a child is non-shared-environment (NSE) rather than shared environment (SE, viz. ”parenting”). The more a parent optimizes for individual agency, the less “parenting” will be attributed.
Claude at least basically confirmed this interpretation (it says it is "slightly overstated" but then gives a "clarification" that doesn't change it). My reaction was "wait WHAT" - doesn't that completely invalidate the whole "parenting doesn't significantly matter for future life outcomes" claim?
Because that claim is based on equating "parenting" with "shared environment". But if you equate "parenting" with just "what are the ways in which parents treat each child identically" then it seems that of course that will only have a small effect.
I for one know that I interact very differently with children with different personalities! (Or, for that matter, with adults with different personalities.) One classic example of this is that children who are naturally compliant and "easy" are disciplined/punished less, because there's much less of a need to do so.
I would intuitively expect that the amount of ways in which parents treat each child exactly the same would be very small. As an extreme case, parents who engage in child abuse may sometimes be abusive toward only some of their children, while treating the rest more or less normally; e.g. because some of the children have traits that the parents happen to intensely dislike. Even if we don't go that far, most parents will get along better with some of their children than others. One child might be more on the same wavelength with mom while their sibling is more on the same wavelength with dad, etc.
How isn't this talked about more as an enormous caveat to those "parenting doesn't matter" studies? (ping @Steven Byrnes )
Claude Opus 4 on non-shared environment claim
is this accurate:
"An intriguing feature of twin studies: anything a parent does to individualize for a child is non-shared-environment (NSE) rather than shared environment (SE). and when people claim twin studies show parenting doesn't matter, they're conflating parenting with shared-environment when non-shared-environment contains parenting too."
This is largely accurate, but needs some clarification.
The statement correctly identifies that differential parenting - when parents treat their children differently - gets categorized as non-shared environment (NSE) in twin studies. This is indeed a crucial point that's often misunderstood.
However, the claim that "anything a parent does to individualize for a child is NSE" is slightly overstated. More precisely:
- Shared environment (SE) includes parenting behaviors that affect all children in a family similarly - like general parenting style, family rules, socioeconomic status, neighborhood, etc.
- Non-shared environment (NSE) includes parenting behaviors that differ between children - like favoritism, different responses to each child's temperament, birth order effects, or tailoring approaches to each child's needs.
The second part is spot-on: when people claim "twin studies show parenting doesn't matter," they're often making the error of equating all parenting with shared environment. Since shared environment typically shows small effects in many twin studies (especially for personality traits and IQ in adults), they conclude parenting is unimportant. But this ignores that differential parenting is captured in the non-shared environment component, which often shows substantial effects.
This is a sophisticated critique of how twin study results are commonly misinterpreted. The reality is that parenting can matter enormously - it's just that the ways parents adapt to and treat each child individually may matter more than their general parenting approach that applies to all children equally.
Claude Opus 4 on factors causing differential parenting
Parents naturally:
- Respond to each child's temperament differently
- Adjust discipline strategies based on what works for each child
- Have different relationship qualities with different children
- Spend different amounts of time with each child based on needs/interests
- Express affection differently based on each child's preferences
- Set different expectations based on each child's abilities
Child characteristics:
- Age/developmental stage - Parents adapt their approach as each child grows, so siblings experience different parenting at the same chronological age
- Gender - Despite intentions, parents often interact differently with boys vs. girls
- Physical appearance - Children who resemble a favored (or disfavored) relative may be treated differently
- Health/disabilities - A child with chronic illness, ADHD, learning disabilities, etc. often receives different parenting
- Birth order - Firstborns often get more anxious/intensive parenting; later children more relaxed parenting
- Temperament match - An extroverted parent might click better with their outgoing child than their introverted one
Situational factors:
- Parental life circumstances - Parents going through divorce, job loss, depression, etc. during one child's formative years but not another's
- Family composition changes - Only children who later get siblings experience very different early years
- Economic changes - One child might grow up during prosperity, another during financial hardship
- Parental learning - Parents often say they were "different parents" to their younger children after learning from mistakes
Relationship dynamics:
- Goodness of fit - Some parent-child pairs just "click" better due to shared interests, communication styles, humor
- Behavioral cycles - A difficult child may elicit harsher parenting, which increases difficulty, creating a feedback loop
- Triangulation - In some families, one child becomes the "peacemaker" or "scapegoat," receiving distinct treatment
- Identification - Parents may see themselves in one child more than another, leading to different expectations/treatment
Unintentional differences:
- Parental energy/age - A 25-year-old parent has different energy than a 40-year-old parent
- Comparison effects - Parents may push a child harder (or less) based on their siblings' achievements
- Time availability - Work schedules, other children's needs, etc. affect how much one-on-one time each child gets
All of these create non-shared environment effects in twin studies, yet they're clearly parenting factors that could significantly impact outcomes.
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My context is most strongly the one where I'm trying to reconcile the claims from therapy vs. heredity. I know we did already agree on one particular mechanism by which they could be reconciled, but just that by itself doesn't feel like it would explain some of the therapy claims where very specific things seem to be passed on from parents.
But yeah, I think that does roughly correspond to arguing over whether the bio-determinist child-rearing rule of thumb applies or not.
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On one hand, this does make sense. On the other hand - as far as I know, even the researchers who argue for the strongest bio-determinist case will make the caveat that of course none of this applies to cases of sufficiently extreme abuse, which will obviously mess someone up.
But... if that is in fact the case, shouldn't it by your argument show up as a shared environment effect?
I can think of a few different explanations:
* Even extreme childhood abuse doesn't have a major effect on life outcomes.
* (Including this one for completeness though I consider it obviously implausible.)
* The level of abuse that would affect life outcomes is rare enough not to be picked up on in the studies.
* The methodology of the studies creates on floor on the badness of outcomes that gets picked up; e.g. maybe adoptive parents are screened well enough to make the worst abuse not happen, and the people drawn from national twin registers and contacted to fill in surveys don't bother responding if their lives are so messed up they don't have the time or energy for that.
* But at least studies that use national registers about e.g. incarceration should be able to control for this.
* There's something wrong about the correlation argument.
When I asked Claude about this, it claimed that actually, studies done with national registers find a significant shared environment effect on antisocial behavior and criminality. It gave me this cite which reports a 26% shared environment effect on antisocial
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Thanks!
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I vote for the second one—the result is usually “shared environment effects on adult outcomes are statistically indistinguishable from zero” but that doesn’t mean they’re exactly 0.00000…. :)
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There are definitely huge shared environment effects during the period where kids are living with their parents. No question about it!
(Also, for the record, some measurements seem to be adult outcomes, but are also partly measuring stuff that happened when kids were living with their parents—e.g. “having ever attended college”, “having ever been depressed”, “having ever gotten arrested”, etc. Those tend to have big shared environment effects too.)
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The result there is “parents are harsher and less warm towards their kids who are more callous and aggressive”, and when you phrase it that way, it seems to me that the obvious explanation is that parents behave in a way that is responsive to a kid’s personality.
Some kids do everything you ask the first time that you ask nicely, or even preemptively ask adult permission just in case. Other kids are gleefully defiant and limit-testing all the time. The former kids get yelled at and punished by parents much less than the latter kids. (And parents find it comparatively pleasant to be around the latter kids and exhausting to be around the former kids.) This all seems very obvious to me, right?
Thus, if per Will Eden “parents think they treat their kids the same… but the kids think the parents treat them differently, and outside observations would support this claim”, I’d guess that the parent would say something like: “the household rule is: I’ll watch TV at night with any child who wants to do that and who sits quietly during the show, and another household rule is: if you jump on the couch then you have to go to your room, etc. I apply these rules consistently to all my children”. And the parent is correct—they are in fact pretty consistent in applying those rules. But meanwhile, the kids and outsid
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Thanks!
Hmm, I think it might be good to sharpen the context a bit more, as I feel we might be slightly talking past each other.
The argument that I'm the most focused on questioning is, to be clear, one that you haven't made and which isn't in your writings on this topic. That argument goes something like, "Kaj, you've written all these articles about emotional learning and about how people's unconscious motives on behavior often go back to childhood and especially to people's interactions with their parents, but heredity studies tell us that par...
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Similar to other people's shortform feeds, short stuff that people on LW might be interested in, but which doesn't feel like it's worth a separate post. (Will probably be mostly cross-posted from my Facebook wall.)