IQ: I don’t want this to be true…

February 12, 2011 at 1:02 am (Articles) (, , , , )

This blog post discusses evidence that inheritance is, fundamentally, more important than upbringing in determining IQ. The original article is here.  The results are striking: when a child is adopted from birth, the adopted parents IQ correlates with the child’s IQ until age 7.  But by the teenage years, the correlation is gone – intelligent parents do not have intelligent adopted children, even though they do have intelligent biological children.  The conclusion is difficult to avoid.

I don't want it to be true...

I have discussed IQ before, and it lead to quite strong disagreement with some knowledgeable people who somehow found my blog.  This is (more) evidence – strong evidence – against the position I took in that discussion.  The view – my view – that genetics should be ignored by society is weakened by these results.  The truth is “obviously” the opposite – genetics do matter, a lot.

I can find some glimmers of hope – some possibilities that nurture may still win, despite the above evidence.  But I doubt that the relative importance of nature and nurture will, in this particular case, be overturned.  These are discussed at the end.

Like a good scientist, I am therefore going to change my mind and follow the evidence, right?  Nope. I’m going to bloody mindedly stand by my opinion that genetics cannot (at least yet) play a role in decision making in society, even though by normal scientific standards it could be counted as a fact.

The scientist with a “non-scientific” view?

How can I possibly justify denying something that I believe to be true?

My reason is that, although we have enough scientific evidence about the effect of genetics on people, we do not have an understanding about the effect of acting on this knowledge. I am petrified by the thought of what decisions might be made on the basis of knowing IQ correlates better with nature than with nurture.  Here are just two that could come about if the idea is accepted into the mainstream:

  1. Intelligent, wealthy, middle classed people will be less likely to adopt from poor and/or unknown genetic stock.  As discussed in the links above, it is not rational to adopt children who will not live up to expectations; instead, IVF and other solutions will be preferred.  This could result in disaster for those needing adoption.
  2. People who believe that they have good genetic stock would rationally want to “out breed” those with “inferior” genetics.  In today’s class society, that would mean specifically preventing poor (or otherwise undesirable) people from breeding.  We’ve seen this before, and it was not pretty.

Do we accept the evidence and put up with the consequences?  I say no – although scientifically we can accept these results, they must not be accepted by society.

The responsible scientist

The correct response, I believe, is to place a stronger requirement on the evidence.  Essentially, we need to know how to move from the society we have now, to a society that might exploit this knowledge, without causing chaos, misery and unfairness on the way.  This requires several things: firstly, an almost unheard of degree of certainty in the scientific evidence that nature trumps nurture, because whilst there is even a glimmer of doubt any policy will be unfair.  Secondly, it requires a strong understanding of the social response that people will have to such a policy.  And thirdly, we must know how to deal with that in a way that is fair.  (a fair rule: we would all agree to it before we know which side of the rule we will fall on.)

The high bar

My previous arguments on  this subject focussed on the first of these points, because I’m not convinced that anyone knows anything about the second and third.  The burden of proof must be with the nature camp, simply because the implications of it being true could be so dramatic.  Therefore I will offer a couple of “get out” clauses to the above research.

Firstly, the results are averages over children that were either adopted or not.  If there is a correlation with e.g. parents IQ and being adopted, then these results will be biased by it. (But that still assumes a genetic relationship for IQ, just a different one…)

Secondly, the results cannot account for the effect of “epigenetics“: that is (mostly), the effect of mothers health during pregnancy on the potential of her child.  As I discussed previously, this effect is these days being seen as large (hence the “no alcohol” taboo for pregnant women…).

Thirdly, there may be social reasons that adopted children do poorly.  If they are told they are adopted, then they may spend their teenage years in rebellion and doubt. If they are not told they are adopted, perhaps the parents still behave differently towards them.

Finally, as I discussed previously, if you assume a (false) social concept is true you may inadvertently make it come come about. People who are believed to have low “genetic IQ” might have low observed IQ – but only because society (and they themselves) expect it to be true.

The most important part of all – disclaimer

In all cases, it is extremely important to remember that these effects are small – they are simply correlations in a whole bunch of causes and effects.  They do not predict what will happen for any given adoption, or indeed natural birth.  Some children do well in terrible circumstances, and others fritter away privilege.  Correlation does not imply causation.  IQ does not measure anything other than IQ – and itself only weakly correlates with intelligence.  What of happiness, life satisfaction, social responsibility, and so on?

See my previous posts and the comments therein for the references I collected on the subject: on race and IQ, and on the existence of races (accidentally about IQ).



  1. Silvia said,

    How about the confidence intervals for those correlations?

    • thinkingdan said,

      I tried to find this out and failed (though mostly due to insufficient effort, I’m afraid) . Its a good point, and needs to be addressed. However, this research seems to be just another drop in an ocean, so my general viewpoint would remain even if this particular research result turned out to be due to publication bias or some such.

  2. Kiwiguy said,

    ***People who believe that they have good genetic stock would rationally want to “out breed” those with “inferior” genetics. ***

    Given the number of social problems associated with low cognitive ability, wouldn’t it make sense for policy makers to at least focus on making it easier for educated women to have children. In most developed countries the tendency is for women to have fewer children if they are more educated. So over time the population is going to be worse off. This is a point that leftist academic Jim Flynn (of Flynn effect fame) has pointed out.

    Another implication is that immigration should target skilled people (if talents are partially heritable). In terms of unskilled immigration this should be from populations that have a track record of assimilation & reasonable levels of achievement. For instance, the US has allowed in millions of unskilled migrants from Mexico. A common argument is that the Irish, Jews and others all started off poor but worked there way up. But that ignores human genetic diversity as well as cultural differences. And subsequent generations are lagging in terms of high school and college education.

    • thinkingdan said,

      I definitely agree that governments should encourage educated women to be able to have children more easily, and to target poorly educated people with birth control campaigns. Whilst I tentatively agree with the IQ part of the reasoning, I think the ethics of this are very murky… however, there are good social reasons for this, because well educated people can provide better for their children and such policies should help break the poverty cycle.

      I also agree that immigration should usually target skilled people (although there are cases where all immigration is to be encouraged, e.g. where populations are falling) – and broadly speaking it does. Again I’m wary of IQ arguments regarding this but agree that they may have merit. For social reasons, assimilation is very important for immigration policies but here I think the IQ argument is less strong. The reason is that immigration brings in new genetic diversity, which is almost always beneficial. Greater diversity leads to a larger gene pool and more material for selection to act on, so assuming (for the sake of argument) that the average IQ decreases in the short term, the number of very high (and low) individuals should increase. But that is all theory, I wouldn’t advice anyone to set immigration policy on it!

      Regarding the “frumforum” link, I think the US is a bad example for these studies because of the huge social divide (in some areas) between races. It is very difficult to rule out social factors when all the immigrants live in communities that are, on average, poor. Perhaps there are studies of people who are genetically mostly “latino” but who do not self-identify as such, and who live in “white” environments; my hypothesis is that these people would be as successful as genetic “whites”. (I hate those labels…)

  3. Kiwiguy said,

    Jason Richwine makes a case that IQ or skilled selection will result in better assimilation & increased social capital (he notes some research by Robert Putman that increased diversity can potentially have a negative effect on this). He bases this on work by Garrett Jones showing increased co-operation by those with higher SAT results.

    Jones also has an interesting paper with Joel Schneider looking at iq and productivity in terms of immigration.

    ***I think the US is a bad example for these studies because of the huge social divide ***

    That’s true. I think a problem with second generations in poor areas is they pick up the worst peer behaviours. So that would hurt their prospects of assimilation/progress.

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