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.
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…. :)
It gave me this cite which reports a 26% shared environment effect on antisocial behavior defined as various forms of crime (property offenses, violent offenses, and drug-related offenses), measured from childhood to early adulthood [20 years], and also cited some previous work with similar findings.
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.)
[Waller et al. 2018] sounds like even identical twins may be treated differently enough by the same parents for it to have noticeable effects?
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 outside observers just notice that one sibling winds up getting punished all the time and never joining in the evening TV, while the other sibling is never punished and always welcome for TV.
In my post I poked fun at a study in the same genre as Waller et al. 2018. I wrote: “I propose that the authors of that paper should be banned from further research until they have had two or more children.” Of course, for all I know, they have lots of kids, and they have babysat and hung out with diverse classes of preschoolers and kids (as I have), and yet they still subscribe to this way of thinking. I find it baffling how people can look at the same world and interpret it so differently. ¯\_(ツ)_/¯
Anyway, that other study didn’t even mention the (IMO primary and obvious) causal pathway from child personality to parental treatment at all, IIRC. The Waller et al. 2018 study does a bit better: it mentions something like that pathway, albeit with an unnecessarily-exotic description: “Evocative rGE reflects situations in which the child elicits an environment consonant with his/her genes (e.g., a callous child frequently rejects parental warmth, causing his/her parents to eventually reduce their levels of warmth).”), and they claim that their study design controls for it. What they mean is actually that they (imperfectly) controlled for the “child genes → child personality → parental treatment” pathway (because the children are identical twins). But they don’t control for the “random fluctuations in such-and-such molecular signaling pathway during brain development or whatever → child personality → parental treatment” pathway. I find that pathway much more plausible than their implied preferred causal pathway of (I guess) “parents are systematically warmer towards one twin than another, just randomly, for absolutely no upstream reason at all → child personality”. Right?
I think the only way to see parental effects without getting tripped up by the child personality → parental treatment pathway is to rely on the fact that some parents are much more patient or harsh than others, which (my common sense says) is a huge source of variation. Just look around and see how differently different parents, different babysitters, different teachers interact with the very same child. That brings us to adoption studies, which find that parenting effects on adult outcomes are indistinguishable from zero. So I’m inclined to trust that finding over the studies like Waller et al. 2018.
By the way, Will Eden cites Plomin, but meanwhile Turkheimer reviews many of the same studies and says the results are basically zero (he calls this “the gloomy prospect”). (Turkheimer is Plomin’s reference 41.) It would be interesting to read them side-by-side and figure out why they disagree and who to believe—I haven’t done that myself.
I’m not sure that explaining it by “maybe parents just have a minimal effect overall” makes things any less weird and counterintuitive!
I don’t find these things counterintuitive, but rather obvious common sense. I can talk a bit about where I’m coming from.
There are many things that I did as a kid, and when I was an adult I found that I didn’t enjoy doing them or find it satisfying, so I stopped doing them. Likewise, I’ve “tried on” a lot of personalities and behaviors in my life as an independent adult—I can think of times and relationships in which I tried out being kind, mean, shy, outgoing, frank, dishonest, impulsive, cautious, you name it. The ways-of-being that felt good and right, I kept doing, the ones that felt bad and wrong, I stopped. This is the picture I suggested in Heritability, Behaviorism, and Within-Lifetime RL, and feels very intuitive to me.
Also, my personality and values are very very different from either my parents’ personalities, or the personality that my parents would have wanted to instill in me.
I guess the childhood trauma thing is important to your intuitions, which we were chatting about in the comments of my post. I can share my first-person perspective on that too: I was blessed with a childhood free of any abuse or trauma. But I’m kinda neurotic, and consequently have wound up with very very dumb memories that feel rather traumatic to me and painful to think about. There is absolutely no good reason for these memories to feel that way—I’m thinking of perfectly fine and normal teenage things that I have no objective reason to be embarrassed about, things in the same ballpark as “my parents walked on me masturbating, and promptly apologized for not knocking and politely left, and never brought it up again”. (My actual painful memories are even dumber than that!) Just as you were speculating in that comment thread, I think I’m predisposed to dwell on certain types of negative memories (I’m very big into embarrassment and guilt), and in the absence of any actual objectively terrible memories to grab onto, my brain has grabbed onto stupid random teenager stuff.
I am able to take the harsh edge off these memories by CBT-type techniques, although I haven’t really bothered to do that much because I’m lazy and busy and AFAICT those memories are not affecting my current behavior too much. (I’m somewhat introverted in part from being oversensitive to social embarrassment and guilt, but it’s not that bad, and my uninformed guess is that finding peace with my dumb teenage memories wouldn’t help much.)
things you do as a parent will have generally small or zero predictable effects on what the kid will be like as an adult
Is there any action-relevant difference between “no effect” and “no predictable effect”?
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 parents don’t affect what people are like as adults, so how do you explain that”.
And it gets a bit subtle since there are actually several different versions of that question:
“Therapy books sometimes give the impression that everything about a person’s life is determined based on their childhood circumstances. How do you justify that, given twin studies?”—Very fair question! Some therapy books do give that impression, and such a claim is clearly incorrect. I’m not going to defend that claim. I think it’s basically a result of selection bias. The people who got lucky enough with their genes that they make it through sucky childhoods without major issues don’t see therapists, and then therapists write books that draw on their clinical experience based on clients that have been selected for having unlucky genes.
“Okay, but even if not everything about a person’s issues is determined by their childhood circumstances, the therapy books still say that stuff like parental warmth is a major factor on a person’s future psychology. But wouldn’t that imply a bigger shared environment effect?”—Also a very fair question, and the thing that I’m the most interested in figuring out/explaining! And I’m trying to explain that with something like “maybe parents have counterintuitively different effects on different children, and also the specific psychological issues this may cause don’t necessarily map linearly to the kinds of outcome variables the studies are looking at”.
“So from twin studies, we know that parents have basically no causal effect whatsoever on the children, so...”—Okay now my imagined interlocutor is going too far, the twin studies don’t say that. Parents still have some causal effects on their children—such as the children having memories of being raised by their parents, that would be different if they’d had different parents! But, I’ve talked with some people who did seem to take their interpretation of the studies that far! So I’d like to at least establish an argument that makes it clear why that is wrong.
And as an aside, when I say “therapy books”, I also mean my own personal experience with coaching people and applying the kinds of techniques the therapy books talk about. Quite often childhood stuff or stuff about parents pops up, even when the questions I ask don’t reference childhood in any way.
So when you say that
I don’t find these things counterintuitive, but rather obvious common sense. I can talk a bit about where I’m coming from.
There are many things that I did as a kid, and when I was an adult I found that I didn’t enjoy doing them or find it satisfying, so I stopped doing them. Likewise, I’ve “tried on” a lot of personalities and behaviors in my life as an independent adult—I can think of times and relationships in which I tried out being kind, mean, shy, outgoing, frank, dishonest, impulsive, cautious, you name it. The ways-of-being that felt good and right, I kept doing, the ones that felt bad and wrong, I stopped. This is the picture I suggested in Heritability, Behaviorism, and Within-Lifetime RL, and feels very intuitive to me.
Also, my personality and values are very very different from either my parents’ personalities, or the personality that my parents would have wanted to instill in me.
Then, on the one hand, I do agree with your reasoning here, and what you say also agrees with my own experience of what I’m like as an adult vs. what my parents are like.
On the other hand, when talking about the study of adolescent/young adult antisociality, you mention that parents do have a significant effect on their children when the children are still living with them. And it’d be pretty weird if the degree of adolescent/young adult antisociality had no effect on what one is like as an adult. That’s especially so since the measure of antisociality in this study was, basically, “has the person committed property crimes, violent crimes, or drug-related crimes”.
From the perspective of questions #2 and #3, I might say: “Whether you commit crimes as an adolescent has to have some predictive effect on your future outcomes. Obviously it’s not a deterministic effect—even if you deal drugs as a teenager and beat someone up for not paying their drug debt to you, it’s still totally possible to put all of that behind you and end up as a well-adjusted adult. But you would expect such a person to be statistically less likely to end up with good outcomes than someone who committed zero crimes in their teens, right?”
“So I’m honestly a little confused how to reconcile ‘significant shared environment effect on crime when an adolescent’ with ‘basically no shared environment effect on adult outcomes’. But maybe it’s just the case that serious crime as youth is pretty rare in the first place, and not getting over it is more rare still! (Especially given that the study covered people who grew up in Sweden ca. 1985-2006.) Still, I would expect that the people who used to commit crime as teenagers will have a different psychological profile than the people who never did, even if their background ends up ultimately not affecting the coarse kinds of variables that the other twin studies measure. For instance, maybe they feel shame and guilt about what they’ve done and will want to process that with a therapist later, or maybe they have some anxiety of their past catching up on them… even if neither of those is the kind of thing that’d be picked up on the twin studies. So I feel like that should answer the skeptical voice asking questions #2 and #3.”
To take another example—when I was a kid, I wore shoes with no laces on them and somehow nobody taught me to tie my shoelaces until I got to a point where it was embarrassing not to know how to do it. As a defensive move, I made it into an identity thing that “I’m not the kind of person who uses shoes with laces”. I continued with that way all the way until I was about to turn 30, at which point I finally acknowledged that I was being stupid, looked up some YouTube video titled “the easiest way to teach your kid to tie their shoelaces”, and taught myself to tie shoelaces.
I’m pretty sure there was a causal connection between that sequence of events and me having the parents that I had, since some other parents would just have taught me to tie my shoelaces earlier. And it had a slight negative effect on my self-esteem during that time. But again neither of those was the kind of a thing that would be picked up on twin studies. (Especially since I don’t have a twin, but never mind that.)
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?
That’s a good point! I definitely agree about that effect.
That said, I think that the effect is bidirectional. Antisocial tendencies cause negative reactions to the person and negative reactions to the person strengthen antisocial tendencies. For example, I’ve heard people express anecdotes like “I realized I was being an asshole and tried to better myself, but then nobody noticed and everybody treated me like I hadn’t changed at all, so I gave up on even trying” or “I was always an asshole so nobody gave me a chance, but then this one person showed up who believed in me even though I kept being a jerk to them, so then I eventually stopped being so much of a jerk to them, and over time I became less of a jerk overall”.
One weakly-held intuition would be that if it’s very hard for parents to overcome their instinctive tendency to react more harshly to a difficult kid, such that almost nobody manages it, then this would show up as a hereditary effect (if the saintly parents who can respond to every child will equal warmth are as rare as the monstrous ones who abuse their kids terribly). And I do think it’s very difficult to overcome that tendency, such that very few people manage it! I like kids and can usually sympathize with even some of the more challenging ones, but it’s still a lot easier for me to show and feel pure positive regard toward the intrinsically easy and friendly ones.
… but that’s only weakly held, because I do acknowledge the point that some parents are still much more patient or harsh than others, so you would expect that to show up as a shared environment effect nonetheless. So I have to fall back on “maybe there is an effect, but it’s counterintuitively unpredictable”. But even then we’d have to disregard the Waller et al. 2018 study, which doesn’t say that the effect would be weirdly unpredictable.
Is there any action-relevant difference between “no effect” and “no predictable effect”?
Thanks!
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…. :)
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.)
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 outside observers just notice that one sibling winds up getting punished all the time and never joining in the evening TV, while the other sibling is never punished and always welcome for TV.
In my post I poked fun at a study in the same genre as Waller et al. 2018. I wrote: “I propose that the authors of that paper should be banned from further research until they have had two or more children.” Of course, for all I know, they have lots of kids, and they have babysat and hung out with diverse classes of preschoolers and kids (as I have), and yet they still subscribe to this way of thinking. I find it baffling how people can look at the same world and interpret it so differently. ¯\_(ツ)_/¯
Anyway, that other study didn’t even mention the (IMO primary and obvious) causal pathway from child personality to parental treatment at all, IIRC. The Waller et al. 2018 study does a bit better: it mentions something like that pathway, albeit with an unnecessarily-exotic description: “Evocative rGE reflects situations in which the child elicits an environment consonant with his/her genes (e.g., a callous child frequently rejects parental warmth, causing his/her parents to eventually reduce their levels of warmth).”), and they claim that their study design controls for it. What they mean is actually that they (imperfectly) controlled for the “child genes → child personality → parental treatment” pathway (because the children are identical twins). But they don’t control for the “random fluctuations in such-and-such molecular signaling pathway during brain development or whatever → child personality → parental treatment” pathway. I find that pathway much more plausible than their implied preferred causal pathway of (I guess) “parents are systematically warmer towards one twin than another, just randomly, for absolutely no upstream reason at all → child personality”. Right?
I think the only way to see parental effects without getting tripped up by the child personality → parental treatment pathway is to rely on the fact that some parents are much more patient or harsh than others, which (my common sense says) is a huge source of variation. Just look around and see how differently different parents, different babysitters, different teachers interact with the very same child. That brings us to adoption studies, which find that parenting effects on adult outcomes are indistinguishable from zero. So I’m inclined to trust that finding over the studies like Waller et al. 2018.
By the way, Will Eden cites Plomin, but meanwhile Turkheimer reviews many of the same studies and says the results are basically zero (he calls this “the gloomy prospect”). (Turkheimer is Plomin’s reference 41.) It would be interesting to read them side-by-side and figure out why they disagree and who to believe—I haven’t done that myself.
I don’t find these things counterintuitive, but rather obvious common sense. I can talk a bit about where I’m coming from.
There are many things that I did as a kid, and when I was an adult I found that I didn’t enjoy doing them or find it satisfying, so I stopped doing them. Likewise, I’ve “tried on” a lot of personalities and behaviors in my life as an independent adult—I can think of times and relationships in which I tried out being kind, mean, shy, outgoing, frank, dishonest, impulsive, cautious, you name it. The ways-of-being that felt good and right, I kept doing, the ones that felt bad and wrong, I stopped. This is the picture I suggested in Heritability, Behaviorism, and Within-Lifetime RL, and feels very intuitive to me.
Also, my personality and values are very very different from either my parents’ personalities, or the personality that my parents would have wanted to instill in me.
I guess the childhood trauma thing is important to your intuitions, which we were chatting about in the comments of my post. I can share my first-person perspective on that too: I was blessed with a childhood free of any abuse or trauma. But I’m kinda neurotic, and consequently have wound up with very very dumb memories that feel rather traumatic to me and painful to think about. There is absolutely no good reason for these memories to feel that way—I’m thinking of perfectly fine and normal teenage things that I have no objective reason to be embarrassed about, things in the same ballpark as “my parents walked on me masturbating, and promptly apologized for not knocking and politely left, and never brought it up again”. (My actual painful memories are even dumber than that!) Just as you were speculating in that comment thread, I think I’m predisposed to dwell on certain types of negative memories (I’m very big into embarrassment and guilt), and in the absence of any actual objectively terrible memories to grab onto, my brain has grabbed onto stupid random teenager stuff.
I am able to take the harsh edge off these memories by CBT-type techniques, although I haven’t really bothered to do that much because I’m lazy and busy and AFAICT those memories are not affecting my current behavior too much. (I’m somewhat introverted in part from being oversensitive to social embarrassment and guilt, but it’s not that bad, and my uninformed guess is that finding peace with my dumb teenage memories wouldn’t help much.)
Is there any action-relevant difference between “no effect” and “no predictable effect”?
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 parents don’t affect what people are like as adults, so how do you explain that”.
And it gets a bit subtle since there are actually several different versions of that question:
“Therapy books sometimes give the impression that everything about a person’s life is determined based on their childhood circumstances. How do you justify that, given twin studies?”—Very fair question! Some therapy books do give that impression, and such a claim is clearly incorrect. I’m not going to defend that claim. I think it’s basically a result of selection bias. The people who got lucky enough with their genes that they make it through sucky childhoods without major issues don’t see therapists, and then therapists write books that draw on their clinical experience based on clients that have been selected for having unlucky genes.
“Okay, but even if not everything about a person’s issues is determined by their childhood circumstances, the therapy books still say that stuff like parental warmth is a major factor on a person’s future psychology. But wouldn’t that imply a bigger shared environment effect?”—Also a very fair question, and the thing that I’m the most interested in figuring out/explaining! And I’m trying to explain that with something like “maybe parents have counterintuitively different effects on different children, and also the specific psychological issues this may cause don’t necessarily map linearly to the kinds of outcome variables the studies are looking at”.
“So from twin studies, we know that parents have basically no causal effect whatsoever on the children, so...”—Okay now my imagined interlocutor is going too far, the twin studies don’t say that. Parents still have some causal effects on their children—such as the children having memories of being raised by their parents, that would be different if they’d had different parents! But, I’ve talked with some people who did seem to take their interpretation of the studies that far! So I’d like to at least establish an argument that makes it clear why that is wrong.
And as an aside, when I say “therapy books”, I also mean my own personal experience with coaching people and applying the kinds of techniques the therapy books talk about. Quite often childhood stuff or stuff about parents pops up, even when the questions I ask don’t reference childhood in any way.
So when you say that
Then, on the one hand, I do agree with your reasoning here, and what you say also agrees with my own experience of what I’m like as an adult vs. what my parents are like.
On the other hand, when talking about the study of adolescent/young adult antisociality, you mention that parents do have a significant effect on their children when the children are still living with them. And it’d be pretty weird if the degree of adolescent/young adult antisociality had no effect on what one is like as an adult. That’s especially so since the measure of antisociality in this study was, basically, “has the person committed property crimes, violent crimes, or drug-related crimes”.
From the perspective of questions #2 and #3, I might say: “Whether you commit crimes as an adolescent has to have some predictive effect on your future outcomes. Obviously it’s not a deterministic effect—even if you deal drugs as a teenager and beat someone up for not paying their drug debt to you, it’s still totally possible to put all of that behind you and end up as a well-adjusted adult. But you would expect such a person to be statistically less likely to end up with good outcomes than someone who committed zero crimes in their teens, right?”
“So I’m honestly a little confused how to reconcile ‘significant shared environment effect on crime when an adolescent’ with ‘basically no shared environment effect on adult outcomes’. But maybe it’s just the case that serious crime as youth is pretty rare in the first place, and not getting over it is more rare still! (Especially given that the study covered people who grew up in Sweden ca. 1985-2006.) Still, I would expect that the people who used to commit crime as teenagers will have a different psychological profile than the people who never did, even if their background ends up ultimately not affecting the coarse kinds of variables that the other twin studies measure. For instance, maybe they feel shame and guilt about what they’ve done and will want to process that with a therapist later, or maybe they have some anxiety of their past catching up on them… even if neither of those is the kind of thing that’d be picked up on the twin studies. So I feel like that should answer the skeptical voice asking questions #2 and #3.”
To take another example—when I was a kid, I wore shoes with no laces on them and somehow nobody taught me to tie my shoelaces until I got to a point where it was embarrassing not to know how to do it. As a defensive move, I made it into an identity thing that “I’m not the kind of person who uses shoes with laces”. I continued with that way all the way until I was about to turn 30, at which point I finally acknowledged that I was being stupid, looked up some YouTube video titled “the easiest way to teach your kid to tie their shoelaces”, and taught myself to tie shoelaces.
I’m pretty sure there was a causal connection between that sequence of events and me having the parents that I had, since some other parents would just have taught me to tie my shoelaces earlier. And it had a slight negative effect on my self-esteem during that time. But again neither of those was the kind of a thing that would be picked up on twin studies. (Especially since I don’t have a twin, but never mind that.)
That’s a good point! I definitely agree about that effect.
That said, I think that the effect is bidirectional. Antisocial tendencies cause negative reactions to the person and negative reactions to the person strengthen antisocial tendencies. For example, I’ve heard people express anecdotes like “I realized I was being an asshole and tried to better myself, but then nobody noticed and everybody treated me like I hadn’t changed at all, so I gave up on even trying” or “I was always an asshole so nobody gave me a chance, but then this one person showed up who believed in me even though I kept being a jerk to them, so then I eventually stopped being so much of a jerk to them, and over time I became less of a jerk overall”.
One weakly-held intuition would be that if it’s very hard for parents to overcome their instinctive tendency to react more harshly to a difficult kid, such that almost nobody manages it, then this would show up as a hereditary effect (if the saintly parents who can respond to every child will equal warmth are as rare as the monstrous ones who abuse their kids terribly). And I do think it’s very difficult to overcome that tendency, such that very few people manage it! I like kids and can usually sympathize with even some of the more challenging ones, but it’s still a lot easier for me to show and feel pure positive regard toward the intrinsically easy and friendly ones.
… but that’s only weakly held, because I do acknowledge the point that some parents are still much more patient or harsh than others, so you would expect that to show up as a shared environment effect nonetheless. So I have to fall back on “maybe there is an effect, but it’s counterintuitively unpredictable”. But even then we’d have to disregard the Waller et al. 2018 study, which doesn’t say that the effect would be weirdly unpredictable.
For parents, you mean? None that I can think of.