Shared environment

Seems to me that there’s an awful lot of overlap between the environmental factors in shared family environment and those that are supposed to explain group differences.

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35 Responses to Shared environment

  1. JayMan says:

    You would think so…

    I also like when people try to explain the unshared/unique environment as events that only happen to individuals – “it can effect me as long as it doesn’t also happen to my twin”.

    How many things make that cut?

    • gcochran9 says:

      Individual cosmic rays.

    • caethan says:

      Random developmental noise – a neuron zigs instead of zags.

    • Janet says:

      Lots of things make the cut, I’d say. For example, things like accidents– falling off your bike is “unshared environment”. Also, diseases that only one person catches, but not the rest; or if a disease has a particularly bad/damaging effect, but only a minority of the people who get the disease, get that effect. Say, measles– probably everyone in the family gets measles, but only about 1 in 1000 gets encephalitis. The measles may be shared environment, but the encephalitis is unshared. A congenital example would be birth injuries that hit one twin but not the other; you could also cite discordant twins due to the placenta of one lying on top of the placenta of the other, i.e. one was less well nourished than the other.

      What I would say is, this sort of “unshared environment” is usually pretty obvious, both of the cause and of the effect. Things like peer group effects are often cited, but it’s hard to actually pin down the causality– is Jimmy stupid because he hangs around with stupid kids, or does he gravitate to the stupid kids because he’s already stupid and is just finding his own level?

  2. ohwilleke says:

    Per a review study from 1998, child IQ and anti-social behavior are the main exceptions.

    • gcochran9 says:

      Adult IQ is more important, nicht wahr?

      In the Depression, the great majority of people lived a life that, in terms of every material factor, was desperately poor, compared to today. Yet they were about as good at learning trigonometry as people are today.

  3. Joe says:

    Could you expand on this a little bit? The main things I hear about explanations for group differences relate to one group being mean to another, which presumably doesn’t happen within a family. Thanks

  4. gcochran9 says:

    There’s been no example of ‘ being mean’ in the US in the last couple of generations. And even when there was, like putting the Japanese in prison camps in WWII, it had no effect on IQ.

    • Joe says:

      True. What specifically are you referring to as a postulated cause of group differences that are also part of the shared environment of families? Having a few on hand would shorten arguments with old academic family members by about an hour and a half on average.

      • Anonymous says:

        Some environmental effects are well established as lowering IQ– malnutrition, exposure to toxins, physical injuries to the brain (either trauma or caused by a disease). The gist of the argument is, if a group (familial, racial, ethnic, caste, whatever) is all exposed disproportionately to one or more of these causes, then the group IQ average will be suppressed by that environmental factor. (Nobody necessarily needs to be “mean” for this to happen, although generally people point to low SES as the reason why a family or group is malnourished, exposed to toxins, etc.) Removing this cause, can then remove the IQ distinction.

        There are some clear-cut historic cases of this sort of thing, such as iodine deficiency in the Alpine regions of Europe leading to Alpine cretinism. Parts of the third world today still show widespread iodine deficiency (and other malnutrition), and so it’s reasonable to think that fixing that would have a beneficial effect on the population’s IQ.

        But three problems, in terms of this argument’s persuasiveness for the modern world: 1) these conditions usually cause obvious other symptoms, such as severely reduced height and goiters in the neck in the case of iodine, yet these sorts of “other” symptoms seem entirely absent in broad racial/ethnic groups in the first world; 2) these situations have become dramatically less common, even entirely gone, in the developed world, yet group IQ differences persist; and 3) this can’t explain why some populations show an elevated IQ, rather than a reduced one (e.g. why are Ashkenazi Jews roughly +1 SD in IQ, compared to the Europeans they lived among? What vitamins are they taking, or short of, that explains this?)

        • Joe says:

          Thanks. Unfortunately, the Seattle schools are (basically) requiring teachers to accept the argument that poverty causes low school performance, African Americans are overrepresented in poverty, and therefore they are overrepresented in low school performance. “There but by the grace of god…” etc etc. Christian doctrine repackaged into white privilege. That’s the environment that people argue cause low performance.

          • gcochran9 says:

            So the whole country must have become idiots in the Depression.

            • Joe says:

              Isn’t that when environmental explanations began to take hold.

            • gcochran9 says:

              Before they figured out how to get at the Bakken Shale, North Dakota was fairly poor. But they were contenders for the highest test scores in the nation. How was this possible?

              Or – China is a lot poorer than the US. Higher scores. Explanation?

              • Groveton, NH, a lumbering town above the Notch with one of the lowest incomes in the state, and bottom 5th percentile for the country, wins an award every few years when people who look at statistics (as opposed to understanding them) notice that despite the high percentage of kids qualifying for school lunches, they also have a good graduation rate for the high school.

                I’ve been working with the mentally ill of the whole state for forty years and doing psychosocial histories on these families. Groveton and other towns have high rates of poverty, incest, abuse, chaos, neglect, substance abuse, lack of medical care – hell, lack of running water and electricity sometimes – yet a lot of them finish 12th grade anyway. Not all, certainly. Yet the graduation rates still exceed those of urban schools. How can this be?

                As Yogi Berra probably didn’t actually say, but might have “You can see a lot just by looking.”

    • Joe says:

      I think this is what you are referring to as supposed gap creators:

      “For example, the general personality and general parenting styles and beliefs of the parents, the socio-economic status of the family, the kind of neighborhood that the family lives in, the number of books in the home, and so on, are all features of the environment that would be common to the environment experienced by all children within any particular family.”

  5. catte says:

    Is this what they call a “vacuous proof”?

  6. Lennart Edenpalm says:

    Aah, an article by Gregory. One feel oblige to read it, why? Because Cochran is curious, he wants to know what is going on. Steven Pinker, Richard Dawkins, Daniel Dennet are his cousins.

    My opinion of the internal debate nature /nurture? As a layman using common sense your parents means a lot, although environment has a say.

    Also, Greg you are giving us all tips of interesting books. Daniel Kahneman´s Thinking fast and Slow is imo a thought provoking one.

  7. Joe says:

    By the way, excellent series of comments by “E. Olson” towards the bottom of this Quillette article on “Three Identical Strangers.” They thoughtfully parry semi-hysterical and fact-starved anti-hereditarians (including ‘but Egypt,’ a standard part of the toolkit) and proved some good links. Any idea who it is, or maybe just a random smart person?

  8. ziel says:

    Anyone whose been around a young child over the past few years knows that they are mesmerized by smart phones and tablets as soon as just a few months old and almost by instinct will tap icons and swipe pictures. So prepare yourselves for the next tool in the environmentalist / denialist toolkit – the Tablet Gap, which will explain all group differences. Black and Hispanic families can’t afford extra tablets – so their kids are reduced to borrowing their parents’ iPhones for only a precious few minutes a day – so of course they don’t score well on tests! You know how obsessed Asians are with devices – of course their children score well on exams! It explains everything! – except the Jews of course – even something as magical as a smart phone can’t hold a candle to studying the Torah for IQ-boosting power.

    • Tanturn says:

      I think the opposite is likely to happen, poor kids will be said to spend too much time in front of screens, while rich kids do more “active,” “intellectually stimulating” activities.

      • ziel says:

        That could be, like Obama lecturing African-American kids to put down the video games. It could go either way – doesn’t matter, as long as there’s a ‘factor’ to point to.

        • E says:

          Funny thing, 10 years ago or so (definitely before Obama had much time as president…) I remember reading a science blurb (maybe in the Sunday paper, maybe in the briefs in some magazine, I don’t remember…) that the decrease in the crime rate from the early 90’s could be explained by the boys and young men who would previously be out committing crime being too busy playing video games (even violent ones) to get out and go mug someone or whatever…

          Anyhow, Obama then told them to stop playing video games, did he?

  9. Greying Wanderer says:

    “environment” mostly = adults = dna one step removed

    people being violent cos they grew up in a violent environment


    the environment was violent cos the adults had violent genes which they passed on to their kids.

    easily testable – get one country to go back to the old way of not being lenient to juvenile crime so they get locked up sooner and breed less and see if the crime rate starts going back down like it did for centuries until the policy changed.

  10. John says:

    Group difference in environment exists today. For example, if you compare North Korea to Mexico or Saudi Arabia, the disparity is huge. The North Koreans are still not getting enough calories to eat. Mexico and especially Saudi Arabia must seem heaven to the North Koreans. Yet IQ points the other way. The North Koreans, in spite of horrible national policies, managed to create nuclear bombs, missiles to carry them etc. They have their own MIC that makes guns and cannons etc. Nothing remotely comparable has come out of Mexico or Saudi Arabia. The Saudis do have access to nuclear weapon from Pakistan, but that is oil money talking.

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