> The conclusion is that shared environment doesn't contribute in any predictable way to the heritability of psychological traits
What a shock it would be, if such a complex object developed through interactions with its environment which are
still largely illegible to current experimental methodology.
Shared environmental effects are not illegible. You longitudinally study multiple children living in the same home and attending the same school and you control for genetics by studying homes where two children have been adopted from different families into the same family,so they share only the same shared environment.
Annnnd... it turns out, it seems, the shared environment doesn't explain more than 1%~2% of the variance.
The methodologies for the twin studies and adoption studies outlined seem, as far as I can tell, like the best possible way to try measure that variable. How else might you do it?
What isnt measurable directly are the non-shared environmental effects which contribute the Lions share of the variance attributable to the environment and represent about half the variance overall. The other half being genetics.
The point is that non-shared environmental differences are essentially random and parents and schools can't manufacture them.
Annnnd... it turns out, it seems, the shared environment doesn't explain more than 1%~2% of the variance.
And yet we have the case of Lazslo Polgar who raised 3 daughters to be strong chess players, two of whom became world class and one who became the best female player ever [1]. How likely an outcome would this be if there had never been a chessboard in the Polgar household (nor a determined father to teach them)? Vanishingly unlikely.
Scott Alexander over at SSC has written about the Polgar household [2], even going so far as to arrange a community fundraiser to pay for Laszlo Polgar's book to be translated into English [3] so that he could review it. There is a lot to be said for the Polgar family's ethnic background being a major factor in intelligence, yet children don't learn chess (or anything for that matter) without exposure to it.
> And yet we have the case of Lazslo Polgar who raised 3 daughters to be strong chess players
Yeah, I don't think anyone has argued that obvious, easily identified elements of shared environment aren't obviously connected to chess skill. That's a very different trait than intelligence.
This is one of my favorite stories. I remember watching the documentary they did on this.
If I say "on average American men are 5 feet 9 inches" and you say "and yet we have Robert Pershing Wadlow who is 8 feet 11 inches"
That just doesn't make the case you want it to make.
We also have the famous Williams sisters of tennis fame who's dad was their coach too.
However, let's focus back on the original articles claim about the "science behind making your child smarter". Specifically we need to zero in on the "make" portion of the claim. That there is something that you as a parent can do to engineer the outcome of having your children be smarter than they otherwise would.
Let's evaluate the case of the Polgar sisters as it relates to that claim. Well, if look at the Williams sisters and the Polgar sisters together we could make the case that it might , perhaps, be possible to engineer the outcome of your children becoming world-class at something. In that case I would expect to see a pattern within categories and not just between, and I would also expect more data points. Perhaps more data points are out there and I would be interested to see as many as possible. The data we really need which we don't have is the data which would shed light on the survivorship bias - "how many tennis coach parents or chess grandmaster parents tried to engineer the same outcomes and failed?". For all the tennis parents out there and for all the effort those parents and their kids put in, their kids performance probably falls on some normal distribution of achievement in the sport. You can generalize that to whatever profession you'd like and for the claim to be true that there was something you could do to engineer the outcome you would want to see a high success rate or at least for the cases that we can find not for them to be statistical outliers. My guess is that they are, but I'm open to revise that position if I can see convincing evidence for it.
Next lets address the part of the claim that relates to intelligence. That there is something you can do to engineer the outcome of smarter children. Are the Polgar sisters smarter or are they better at chess? We have it on excellent authority that they are very, very good at chess. Lazslo's book is called "How To Raise a Genius!". Are they geniuses? Does it require a genius to play chess? Does it require a genius to become a chess grandmaster? Are the average life accomplishments of Chess Grandmasters in line with what we would typically call genius? Are you a genius if you can operate in the very narrow domain of moving plastic toys around a wooden board?
Not to diminish the accomplishment or belittle chess players. My point with that is I think there is a conflation between genius and expertise in a very narrow domain. We see natural born geniuses go on to pick a certain field and produce results in it, but we don't normally see parents training kids to be geniuses in a particular field.
Their story is one of my favorites and I think about it often. But you have to ask a few questions... does it generalize to different domains? Maybe it does. Maybe it doesn't. I suspect it does. Can it reliably be repeated and systematized? Perhaps, but I suspect not. Is that at all practical and useful to the average parent? Probably not?
I actually think his experiment and it's result make a lot of sense. He trained them from the age of 3. They fought hard with the government to be allowed to home-school them so they could focus on a curriculum of their choosing, so they had control over what the girls were required to do academically. They made them practice hours and hours a day. The girls, as I recall, loved it. They loved chess. That helps. Lazslo also likely devised good learning strategies. It was a completely unorthodox experiment.
Overall I'm not surprised he got those girls to where he did. I also think that as a pedagogical method it is stunningly impractical for society as a whole to try and model, so I'm not sure it's useful even though I actually think he's right on the money. The traditional education system is not really designed for education, it's designed for credentialing. You have to focus on the lowest common denominator in order to meet the required throughput with a given consistency of results. If you wildly adjust the parameters of the system to say OK what about if we only need to educate three people and we can choose the design goal of the education system? You can certainly wind up with the result that he did. Does that make them smarter? Or does that just make them hyper-capable in a narrow domain?
I think back to my own educational experiments over the years with regards to language learning and compare my results with the results of learning languages inside the university system. It's worlds apart in terms of results. I can personally do it 3x faster on average. I'm undertaking a new experiment in 2019 to deeply learn psychology. We'll see where that winds up. Suffice to say you can most definitely get out-sized results with regards to education if you're in control of the system, you're very capable at devising novel learning strategies and you aren't required to mass-produce results.
I think you looked at my example and thought I was trying to make a much stronger claim than I was really trying to make. Your original post stated that experiments have shown environment can account for only 1-2% of the variance. I used the Polgar sisters example to show how preposterous that is. If Laszlo Polgar hadn't trained his daughters at chess, they wouldn't have been 1-2% worse at chess, they likely wouldn't know how to play chess at all. That's a huge difference!
It's such an obvious claim that I feel almost embarrassed in making it, yet it's an important one. If Richard Williams had never handed his daughters tennis racquets, they would never have won Wimbledon. Similarly, it doesn't matter if your child scores 180 on an IQ test, if he never cracks open a math textbook in his life then there's no way he's winning an IMO gold medal.
Environment makes all the difference. Math textbook beats no math textbook every time. Same goes for tennis racquet and chessboard.
While IMO gold medal is one bar, a lot of people could qualify for the USAMO without "cracking open" a math textbook, just coasting through school and doing homeworks (or not doing them). Of course, 9-12 years of math training is a lot more than never having picked up a tennis racket.
Since 2002, the USAMO has been a six-question, nine-hour mathematical proof examination spread out over two days. (The IMO uses the same format.) On each day, four and a half hours are given for three questions.
Maybe the high school math curriculum is way different in the US, but as a Canadian in second year of university studying math, I had never written a single proof until my first year calculus and algebra courses. I have a hard time believing any kid, no matter how smart, could qualify through that exam without opening a math textbook and only doing homework on normal math problems from high school.
Qualifying for the USAMO doesn't involve proof-based mathematics. It involves the AMC and AIME. At least in the early 2000's, a bunch of people would just get told by their teachers they're taking the AMC math contest one day, and do well on it, then do well enough on the AIME to qualify.
You seem to completely completely misunderstand the claim. 1% ~ 2% of the variance of what?
You haven't shown it is 'preposterous' at all. You haven't shown anything. You have presented a single outlier and interpreted it poorly.
A meta-analysis of broad statistical analyses of a large number of people controlling for genetics and shared environment that looks into house after house after house and concludes that on average 50% of the variance of individual psychological traits is genetic, 1% ~ 2% is attributable to shared environment and the rest is attributable to non-shared environment isn't magically negated by one outlier appearing.
For starters in both cases the girls share 50% of their DNA. Your data point just isn't making the case you think it is. To figure out the variance attributable to shared environment you have to get a statistically significant result with the right controls in place in a well designed study. And then that has to be replicated across many studies to be considered reliable.
It doesn't make the case that siblings turn out much more similar than that in the general population due to being raised in the same home and/or going to the same school. The claim doesn't even suggest that you will never see a household where two siblings are very similar.
It's not at all obvious that if Richard Williams never handed them a tennis racquets that they wouldn't have won Wimbledon. You can't possibly make the claim there was a ZERO percent chance they wouldn't find tennis on their own or through school or through friends and get interested in it and become good. Or that they wouldn't find some other sport. Generalize the thought experiment across many many pairs of sisters where their father tries to coach them in something and what do you find? Does the conclusion you draw from a single data point have predicative power as it relates to what you would expect to see in the general population?
Is it equally as 'obvious' that if Roger Federer's parents never turned the on the TV where he saw tennis and became obsessed with it that he would never have become a tennis champion? His sister is a nurse too, not a tennis champion.
Robert Plomin, in Blueprint, makes the case that what our parents and schools do for us pretty much comes out in the wash as we make our way into adulthood and that throughout our lives our individual choices shape our environment greatly based on what we choose to spend our time doing and what who we choose to hang out with. And he states that our genetic propensities nudge us in the direction of making the choices that shape the environment that in turn shapes us. What parents and schools do has very little predictive power as to how their life will turn out.
If Roger Federer's parents had refused to let him play tennis, then he would never have become the champion he is today.
Genetics may be a necessary condition to be a tennis champion but it definitely isn't sufficient. If Roger Federer had been kidnapped as a baby and raised by central African warlords, he would not have qualified for Wimbledon, let alone won it as many times as he has.
You've looked at a bunch of statistics and left your common sense at the door. People's lives are vastly more malleable through parenting than a mere 1-2%. Parents have the ability to give or take away any opportunity you could think of.
A kid with no known "piano playing genetics" (whatever that means) to speak of, adopted by a wealthy family that owns a grand piano and makes piano lessons mandatory for all of their children is going to be a hell of a lot better at piano than if Glenn Gould's (hypothetical) child were adopted by a poor family who could never afford lessons.
They're not systematizable ever. We're talking about experiences unique to each individual.
If you get 30 kids sitting in a classroom they share the room they're in and the words the teacher is saying. They don't share how much attention each one is paying, they don't share the same comprehension or interpretation of the content, they don't share the way they feel about the content, they don't share the thoughts they have about the content and they don't share the new connections made in their brain as the lesson progresses.
What a shock it would be, if such a complex object developed through interactions with its environment which are still largely illegible to current experimental methodology.