Genetics and intelligence

[eckadimmock]

Hi James,

Let me first say that I enjoy your site and your forum, and I generally agree with what you have to say. However, my first post here is to disagree with you! You rebuke your minister of education (I should mention I say "your" because I'm writing from Australia) because he disregards genetics as a basis of intelligence. I hold no brief for him, but I do have a couple of comments on intelligence.

Firstly, there is no absolute consensus on what intelligence is. Traditional IQ theorists regard it as a unitary factor that can be measured through tests. Others (like American psychologist Robert Sternberg) regard it as culturally defined and consisting of successful adaptation to an environment. It probably is at least partly genetic, but genes provide the potential, not the end result. Consider, for example, height. You may have the genes to be 7 feet tall, but if your parents don't feed you, you'll never reach it.

Then there is the Flynn effect. A New Zealand researcher found that IQ results people in the US and elsewhere had improved by some 10-30 points in a few decades. There's no way their genes had changed that fast!

As for the connection between money and intellect: well, partly, but remember rich parents are more likely to lavish books, computers and other learning aids upon their kids. If money=intellect, we'd have to conclude that Paris Hilton is a genius and terminally strapped-for-cash Mozart was an idiot!

Genetic determinism, and IQism in particular, has been behind a lot of injustice in the 20th Century, not least in the UK. I realise it's not your area but if you're at all interested in the subject of race, class and IQ, Try www.seekbooks.com.au/featuredbook1.asp?storeurl=seekau&bookid=9780335203604

Rationing education, by Gillborn and Youdell. It discusses the social justic issues in the British context.

(not sure if the link worked)
Colin

[James Hannam]

Hi Colin,

Thank you for your feedback. First, I should say I agree with most of what you say. On IQ and the difficulties of any objective measure of intelligence, you are quite right. It is also quite wrong to use genetics as a reason for discrimination. But I expect, when push comes to shove, you would give 'nurture' rather more influence than I do.

However, I think my post remains accruate. You accept that genes provide the potential but that needs to be used. So, you should have no argument that two parents with 'potential' are more likely to give birth to offspring with 'potential'. Secondly, if you are unlucky enough to lack the potential, then being treated as if you do will be a waste of what other talents you may have.

So if genes don't give you enough potential, no amount of education can make up the deficit. Therefore, alas, not everyone will get the 5 GCSEs that Adonis considers the a minimum for everyone to aspire to. And, simply because genetics works the way it does, those with clever parents will always have a better chance of inheriting the potential than those who don't.

Not pleasant, but alas, true.

Best wishes

James

PS: I've repaired the link.

[eckadimmock]

I supose it depends on your definition of intelligence. Olympic athletes, pop stars and supermodels have money lavished on them, while many scientists struggle for funding. I don't believe that they are more intelligent!

Not everyone can make the same use of education, but I'd be wary of coupling that with parents' income. That would be a self-fulfilling prophecy.

[James Hannam]

I certainly never coupled intelligence to money. I just said that being clever will usually earn you more money than otherwise. A few hundred footballers, actors and supermodels don't change the fact that to be one of the 750,000 odd high earning accountants, lawyers and bankers in the City, you have to be pretty bright.

And if you are pretty bright, your children are more likely to be than if you are not. As I've said, this may be unpleasant but it is a brute fact of life and we do no one any favours if we refuse to face up to it.

Best wishes

James

[humphreyclarke]

James is absolutely right about the hard hereditary issue. This is the view revealed by the modern Neo-Darwinian synthesis. I'm not convinced its necessarily a bad thing though. Would the world really be better off with more accountants, lawyers and bankers and less big brother contestants, minicab drivers and PE teachers?. Personally I am very happy that the stupid are here to stay, until Eugenics comes back in fashion that is. Blessed are the News of the World and Sun readers.

[eckadimmock]

Well, I don't necessarily disagree that there is a genetic factor, but I think it is often masked by sociological factors such as educational advantage and racism.

Genetic determinism is also worrying in the political context because it is used as an excuse for inaction: since the poor are as thick as two short planks so why waste money on them? You can see this in the racial theories of people like psychologist Arthur Jensen (who felt that many black people were simply ineducable).

A sociologist (Kamin) wrote "There are few more soothing messages than those historically delivered by IQ testers. The poor, the foreign born and racial minorities were shown to be stupid. They were shown to have been born that way. The underprivileged today are demonstrated to be uneducable, a message as soothing to the public purse as to the public conscience".

Hey, we in Australia are sensitive about such issues: you kept the aristocrats and we got the convicts!

[James Hannam]

Sept 1, 2008 22:21:53 GMT eckadimmock said:

Hey, we in Australia are sensitive about such issues: you kept the aristocrats and we got the convicts!

So you got the clever ones!

[James Hannam]

People who continue to be dubious about this should check out International Handbook of Personality and Intelligence (Donald H. Saklofske, Moshe Zeidner eds.) 1995.

Much of it can be read on Google books. A typical quote summarising adoption studies:

“Data imply that the value of the influence of the shared family environment on adult intelligence is close to zero.” p. 62.

In other words there is no correlation between upbring and adult intelligence. There is a correlation between child intelligence and upbringing but they grow out of this.

[eckadimmock]

If you want to pursue this, I must dig out a couple of studies: one where the authors (psychologists) demonstrate a link with social expectations: they told a group of subjects that data suggested that left-handed people were less intelligent than righthanded (which is absolute rubbish) and the subsequent experiment would demonstrate this. They then administered IQ tests (raven Matrices, from memory). Lo and behold, the lefties did perform poorly even though the same people had slightly better college entrance scores!

Also, I'd be interested in your thoughts on the Flynn effect: www.indiana.edu/~intell/flynneffect.shtml can genes change so much in a couple of generations?


If there is no correlation between upbringing and adult intelligence (by which I assume he means IQ test scores?) then aren't parents wasting their time trying to encourage intellectual pursuits?

This is a debate that has been going back and forth since the 1920s, when researchers were happily proving that men were smarter than women, country dwellers were stupider than city dwellers, and that white anglo-saxon protestants were the best and brightest. (Coincidentally, the researchers were WASPS).

On the lighter side, try the Chitling Test wilderdom.com/personality/intelligenceChitlingTestShort.html which is a semi-serious attempt by a black American sociologist to demonstrate cultural bias: it's based on African-American culture.

[James Hannam]

Hi there,

Yes please do dig the study up. I have an idea how/why it works.

We are hamstrung by the fact that IQ tests are so poor as data. But the fact there is no correlation between adult IQ and upbringing is strong evidence that there is no correlation with general intelligence either.

Best wishes

James

[eckadimmock]

I don't think the question is quite as resolved as you appear to imagine, James.

"Such home variables as quality of language models available to the child, opportunities for enlarging vocabulary through appropriate language usage, and opportunities for language practice were also found to be important factors showing a .69 correlation between total ratings of the home environment and general intelligence’ (Hanson)"

allpsych.com/journal/iq.html

(Although it does go on to acknowledge a significant genetic component)

There is also the question of how much genes create an environment. Good looking children, for example, tend to get more attention from adults and hence may develop better social skills than...say, people like me!

Regards,

Colin

[James Hannam]

Sept 5, 2008 11:36:01 GMT eckadimmock said:

Such home variables as quality of language models available to the child, opportunities for enlarging vocabulary through appropriate language usage, and opportunities for language practice were also found to be important factors showing a .69 correlation between total ratings of the home environment and general intelligence’ (Hanson

allpsych.com/journal/iq.html

Hi Colin,

Quickie point. The Hanson study was in 1975. It almost certainly made no allowance for genetics (nothing in those days did) so it is probably useless. That's part of the problem in this debate - any study which does not factor in genetics as primary input is going to give the wrong results. So Hanson doesn't help you.

The 1995 study by Wahlsten (cited on the same site) on moving poor kids to rich households looks a lot more useful. There is some correlation between tested intelligence and upbringing in children but it disappears in adulthood.

Best wishes

James

[eckadimmock]

Ah, put not thy faith in geneticists. (and genetic theories go back to the 19th Century, with studies over a century).

Here's a page on the methodological issues cscs.umich.edu/~crshalizi/weblog/520.html

This person, a Prof of stats at Michigan university, cites Devlin et al 1997 as the best estimate he as seen of the estimate of heritability of intelligence, being based on a metaanalysis which altogether represents a very large twins study or 57,000 odd people. They estimate "the narrow-sense heritability of IQ at 0.34 and the broad-sense heritability at 0.48"

A couple of bits. First, on your quant atitive geneticists:
"To summarize: Heritability is a technical measure of how much of the variance in a quantitative trait (such as IQ) is associated with genetic differences, in a population with a certain distribution of genotypes and environments. Under some very strong simplifying assumptions, quantitative geneticists use it to calculate the changes to be expected from artificial or natural selection in a statistically steady environment. It says nothing about how much the over-all level of the trait is under genetic control, and it says nothing about how much the trait can change under environmental interventions. If, despite this, one does want to find out the heritability of IQ for some human population, the fact that the simplifying assumptions I mentioned are clearly false in this case means that existing estimates are unreliable, and probably too high, maybe much too high. "

although "So, if I like this study so much, and it puts the narrow-sense heritability of IQ at 0.34 and the broad-sense heritability at 0.48, why do I say that we presently know squat about the heritability of intelligence? Partly this is because I deeply object to the confusion of "IQ" with "intelligence", but that's a subject for the sequel. Even if we stick to IQ, whatever that might be, though, I don't see how this study, or any similar one, can really answer the question on technical grounds. It's about as far as you can go within the classical assumptions, but those assumptions are horridly shaky."

The Devlin et al study: www.nature.com/nature/journal/v388/n6641/abs/388468a0.html
cscs.umich.edu/~crshalizi/weblog/520.html

The author's CV is here:

www.cscs.umich.edu/~crshalizi/cv/cv.html

[James Hannam]

Hi Colin,

Thanks for posting the article which I have now read and enjoyed enormously.

If you skip back through my posts, you'll see that I have always maintained hereditibility was about half. I see that our best estimate for the "proportion of total phenotypic variance at the population level that is contributed by genetic variance" is 0.48. So no argument there.

I also note that the author of the article is, like me, a bit of an ultra, although in the opposite direction.

Four quick points. Firstly, IQ as we all agree, does not correlate so well with general intelligence. For a start, IQ has a higher 'environmental' component then general intelligence (as is obvious from all the criticisms raised against it). That is why I have never talked about IQ specifically although it is all we have numerical data for. But, we would expect the heredibility of general intelligence to be higher than for IQ. That said, I'll stick to my figure of a half.

Secondly, if intelligence is not, to a material extent, heritable, then we could not have evolved it. Therefore, it must be.

Third, if the model is as wrong as our author believes, it could easily go the other way.

Finally, experiments on all aspects of character and other traits have been reasonably consistent in finding that hereditibility is about half. Likewise, shared environment always looks like a pretty weak factor. That, in itself, means we should expect intelligence to do the same thing.

Best wishes

James

[eckadimmock]

Glad you enjoyed it! I don't deny there is probably some genetic component, but intelligence is not as straightforward as eye colour or height. It's multifaceted, very subjective and judgments are influenced strongly by social prejudices and fashions. It's rather like good looks: good looking parents are likely to have good-looking children, but what constitutes "good looks" can change over time.

My original point was that in an educational or political context, genetic assumptions should never be used to set policy. I realize you don't go that far, but there are many who would (and have) particularly in regard to race.

Best,

Colin