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Christopher Horn

I certainly can't type fast enough to have posted my last comment before I read Mr. Sailer's. I need to go to sleep, but I have one thought in reply to his post:

Rather than focusing on racial differences in genetic makeup as they impact outcomes in hard-to-define areas such as intelligence, a more parsimonious approach would be to identify individuals that we all agree were intelligent, in a particular area, and determine whether their offspring or other relatives show the same type of intelligence.

The gene mapping you refer to will undoubtedly prove that blacks, whites, hispanics, etc., while sharing the overwhelming majority of genes, also have some specific genetic differences that are no doubt important.

How those differences flesh out in as murky a topic as intelligence will probably be hard to conclude.

It would be much cleaner to find folks you know to be intelligent and ascertain whether their progeny displayed similar intelligence.

Not an easy task, since you would need to be quite particular in identifying the intelligence in question...so for example, it might be tempting to attribute a particular gene for "creative real estate genius" to the remarkable father/son combo of Fred and Donald Trump...but look closer and you might conclude that there isn't much of one man's brilliance that is applicable to the other's...



neither Sailer nor anyone else is arguing that human behavior is 100% genetically determined. Do yourself a favor and read Sailer's blog -- among other things, he has written about why scions of prominent families tend to be less prominent (regression to the mean).

There's a word missing from my reply to Ben Guest. It should read: "... but this does NOT mean that IQ is not determined..."

Christopher Horn


"Regression to the mean"? That argument might be the worst of all for the genetics crowd. 'Regression to the mean' - by definition - means that an observed instance is an outlier, *not* reflective of inherent characteristics, and certainly, certainly! not due to a genetic difference.

For consideration: a cultural example of "regression to the mean" is the Sports Illustrated cover jinx. The argument there is that a team that makes the cover of SI has performed at the upper (successful) end of their distribution of outcomes, and after they make the cover they revert back to their true selves, that is to say, lose again, thereby proving the jinx.

If it follows from your argument that successful industrialists, leaders, intellectuals, etc, are those rare individuals way at the tail end of their distribution of genetic outcomes, then -

- their genetics might be a factor -

- but their genes, under normal circumstances, aren't all that special, yes?

By the regression to the mean argument, such folks, like teams on the cover of SI, more or less got lucky, and the genetics argument therefore couldn't possibly carry much weight.

Ben Guest

Albatross and JL,

Good points. Thanks for the info.


It is not at all clear that 'dramatically increasing the educational resources available to inner city kids' will be effective. The fact that improvements in socioeconomic status increase IQs says nothing about whether throwing more money into education will have similar effects. The improvements may just as likely be associated with cultural differences between the types of families that are poor and those that are middle or upper class. Placing the causation directly on income causes one to overlook the types of behavior that cause a person to be more or less successful.

Phil Downs

Wouldn't it be great if we all woke up Christmas morning and found out that Sailer is really a nom de plume of Gladwell's! What a great gift. I see a screenplay in that, or maybe an SNL skit.

After twenty three years as a public school teacher and administrator, I can only offer anecdotal evidence to this august debate. It seems to me, after watching kiddos from a wide range of socioeconomic backgrounds, and seeing a wide range of performance within families, that there is a genetic boundary to talent of all kinds, which includes, but is not limited to academic performance. Environment seems to be those factors that move an individual to develop those talents necessary for survival and/or self-actualization.

The reality is that none of us reaches her/his genetic potential, but we are all dealing with the shadows of our environments. And so my last comment would be that programs like Head Start won't change our genetics, which we will never maximize, but will enrich the environment of disadvantaged children. As a graduate of Head Start, I disagree that it was a waste of money.

Happy holidays and Malcolm, please make the post on Christmas morning.

Lorna K

Interesting posts. Wouldn't there have to be some linkage between pigmentation genes and 'intelligence' genes if there is indeed a link between race and 'intelligence'? I mean race is simply the ability to make or not make melatonin, IMHO. We would have to assume that the 'intelligent' gene(s) locus(loci) exists close to the locus of one of the genes responsible for making melatonin. I'm sure one could check to see if mutations in pigmentation genes segregate (no pun intended) with those of 'intelligence' genes (when they are found that is). But if there is a link, how would we explain so-called 'intelligent' Africans and 'unintelligent' whites? Doesn't existence of these groups alone support the ideas that 1. IQ and race are not related and 2. that measuring intelligence is RETARDED!! Ha! Back to being serious, the truth is that the ultimate experiments needed to show that one's genetics are necessary and sufficient to cause low or high IQ, will never be done. It would involve first finding the 'intelligent' genes. Second, they would have to be inhibited (most likely pharmacologically) in a human (a smart white one) and result in a loss of intelligence. Finally, the same genes would have to be activated or introduced in a dumb African and, if they are 'smarter' than they were before, the case would closed. Of course appropriate controls would have to be included.

Lorna K

slip, i meant melanin not melatonin!! LOL



It is not helpful that you keep diverting the discussion to completely irrelevant phenomena such as the later life of Woodstock hippies or the "Sports Illustrated cover jinx". They have nothing to do with whether or not there are hereditary differences in intelligence between races. The idea that IQ is genetically determined to a significant degree is completely mainstream among intelligence researchers (http://tinyurl.com/n3bta ), because that is what the preponderance of evidence suggests. Because IQ is normally distributed in a population, and because genes affect IQ, we are likely to find regression toward the mean when we compare IQs of parents and children.

Let's consider a less controversial inherited trait: height. Let's say there are two people, Dick and Jane, who are both 6'5". No one would suggest that they are so tall just because they had better nutrition than the average child, or that their height is due to some other fortuitous environmental factor. Instead, they are tall mainly because they happened to inherit a combination of genes from their parents that strongly predisposed them to grow tall. Now what if Dick and Jane have children together -- how tall will they be? From empirical studies we know that the children will likely be shorter than their parents but still taller than the population mean. This exemplifies how heritable traits can regress toward the mean.


Lorna K-

Your argument falls apart at the starting gate when you assert that race is determined by skin color. No racial classification system that I'm aware of is based on skin color only. Races do not differ from each other only in outward appearance; the fact that there's great racial variance in allele frequencies at numerous loci proves this. Some of these differences are uncontroversial -- for example, adult lactose tolerance and resistance to certain diseases.

However, in the near future we are likely to find genes that explain much of the differences in intelligence, both within and between races. In fact, if it turns out that there are no genetic intelligence differences whatsoever but all people have identical genetic endowment for intelligence, I will forsake my godless ways and become a good Christian! This is because it's astronomically improbable that millenia of reproductive isolation would not bring about differences in cognitive abilities between populations; only an Intelligent Designer could have made all people equally smart.

Your argument that the existence of dumb whites and smart blacks disproves something is also bunk. IQ is normally distributed, which means that there are some whites and blacks at all intelligence levels.

If and when genes for intelligence are found, there is no need for the kind of inhumane experiment you describe. If we can predict a person's IQ score with, say, 80% confidence just by peeking at his DNA sample, there is no need for more evidence. Like Sailer says, journalists and intellectuals should prepare themselves for this eventuality, and start thinking about the ethical and other problems the genetic revolution engenders.

Christopher Horn


The most interesting aspect of your linked manifesto is the quote that two siblings are expected, based on the 'best' genetic research, to be about 12 IQ points apart.

That means my sibs and I are +/-0.8 standard deviations away from each other...due solely to genetics.

One standard deviation around the mean of a normal distribution is 68% of the population. For simplicity, let's suppose that 0.8 standard deviations is roughly 50% of the population.

This would mean, based on your link, that knowing that I was of average intelligence, you could predict my full sibling's intelligence would be somewhere within, oh, 50% of the remaining population. This in spite of the fact that my sibs and I share 50% of our genes. Within a race, where much less than 50% of the relevant genes are shared, perhaps you can find one individual's IQ knowing the IQ of a racial conspecific within what...80% of the total population? 90%? That's pretty exciting stuff!

In conclusion, then, keep fighting the good fight for the genetic impact on racial IQ differences...you'll forgive me if I don't exactly await the learnings with bated breath.


Very good Blog



Someone like Charles Murray, who takes the former position, uses it as explanation for why he think social programs--like Head Start--are a waste of time and money.

The other evidence being that Head Start doesn't seem to have any effect.

Turkheimer's research is easy to explain: all else being equal, people on the far ends of the bell curve will have a great proportion of their IQ difference explained by environment than those near the middle. Especially at the far left of the distribution, you're almost guaranteed to find lots of people who starved, didn't get enough iodine, were exposed to harmful chemicals, etc. Meanwhile, since there aren't any known ways to boost IQ through environment (except with fish consumption, I believe, and that's only a few points), the far right of the bell curve is less environmentally influenced than the far left.

A simple summary, that should explain Turkheimer's results: there are many more non-heritable IQ-reducing effects than there are non-heritable IQ-increasing effects, so studies of low-IQ groups will show more reversion to the mean.


So the way for me to win a debate is to exaggerate my position so much that the midpoint between what someone else says and what I say is what I really believe? Also, what about conspiracy theories: do you think the government did half of 9/11?


"Regression to the mean"? That argument might be the worst of all for the genetics crowd. 'Regression to the mean' - by definition - means that an observed instance is an outlier, *not* reflective of inherent characteristics, and certainly, certainly! not due to a genetic difference.

No, it means that if you have a phenomenon that is the output of one roughly fixed variable and one more or less random variable, the average is likely to drop after an attention-getting extreme. For example, let's say you're measuring the support of various politicians, and your numbers are accurate to within 2%; it is very likely that a candidate whose support goes from 4% to 8% overnight will end up back around 6% the next poll, because the change is due to the random variable (measurement error) not the underlying statistic (support).

Eric Gunn

I don't even understand the purpose of this debate. If we measured the population of every person on earth and found that Asians had a higher average intelligence than Blacks, would that mean that every Asian person was smarter than every black person? Of course not. The intelligence distribution of a population says nothing about the intelligence of an individual within that population. So again, what is the point of this debate?

Christopher Horn

Eric raises a valid point to the extent that, come some future day, we might know for sure whether "whites" are smarter than "blacks" (or vice versa), since we might eventually have a complete IQ profile for every individual, and it will simply be a matter of comparing the IQs of each race's members to see which is smarter.

From a statistician's perspective, on that day the difference in IQ between the races will be 'significant', even if the mean IQ of one race is 100.001 and the mean IQ of the other race is 99.999. When statisticians speak of significance, they are only referring to whether a sample is really representative of a population. Once you've sampled everyone, by definition you've got the population, so by definition any difference is significant.

But between us folks who aren't professional statisticians: would we consider such a difference "meaningful"? And what the heck should you do with that information?

Lorna K

Those 'inhumane' experiments would have to be done to prove a link exists between genotype and phenotype (loss and gain of gene function). Pick up any human genetics paper from a reputable science journal and you will see that peeking at DNA and jumping to conclusions is not enough. Welcome to the world of forward genetics!! You have to test your hypothesis.
I was thinking the same thing!! How big are these differences and at what point should we care or not care?? I think it is telling that the same people who believed the pseudo-science of correlating head-size and intelligence, are the same people trying to spin genetics to make the same argument. My spiritual friend summed it up nicely "dna seems like tarot cards in a way. the card is what it is, there is no getting around that. so, while remaining within certain known boundaries, fortunetellers throughout the world read that card millions of different ways." Come on people ... don't let your arrogance miss the point because she mentioned tarot cards! I'll only add that the different readings in this case haven't been tested empirically and until then, Watson, Saletan and those who agree with them are just fortunetellers. I'll spend my money on something else.

Dane Cao

"So the way for me to win a debate is to exaggerate my position so much that the midpoint between what someone else says and what I say is what I really believe? Also, what about conspiracy theories: do you think the government did half of 9/11?"


I'm not exaggerating my position,quite the contrary,if you read closely,I'm exactly trying to be LESS extreme, endeavoring to tease out the truth with a milder,hormonious approach.Believe it or not,There's indeed some uncanny truth in some ancient propositions,like confucian philosophy,having been tested throughout thousands of years. That being said, I'm not tending towards the GOLDEN MEAN just because it's convenient, but because I truly believe it's the best way to explain the paradoxical issue at hand.

And Don't bring 911 into this.There're too many emotion-fanning elements in it that defy clear and rational thinking.But you may still try to come up with a "golden mean" theory and see if it fits.

Chris J

Very interesting discussion. My two cents.

1. As mentioned previously, I think we should be willing to live with whatever result science reveals and not distort science so that it doesn't offend our sensibilities. However we must also realize that science can be misapplied and misinterpreted and therefore we shouldn't be against challenging conventional science widsom either. What science has "proven" (or more correctly what we believe science has proven) has been shown to be wrong in the past and we will discover it to be wrong on issues in the future.

2. My second point is one that Malcolm raised in his article, the the validity of IQ tests in the first place. We've been throwing around the term IQ and have been debating a link between genes and IQ, but it can be argued that we've yet to find an ironclad way of measuring intelligence. When we have genes completely mapped out before and compared them with IQ scores that still might not necessarily mean that the race (assuming there's a "meaningful" difference between races) that scores the best is the most intelligent. It just means that the race that scores the best is the best at what the IQ tests measure. (Obviously taking environment and variables into consideration.)

3. Thirdly, I feel this is largely an academic discussion for several reasons. One as Eric pointed out is the distribution within the population. People with the smart gene (if it exists) may be really smart or they may not be. As mentioned we rarely actualize potential. For instance, if there is a smart gene, and if someone possesses it, there's no guarantee that he'll have the drive, tools, opportunites, or congitive environment to take full advantage of it. There enough other factors that play into the development how intelligent one is, that the genetic component to me is trivia. Furthemore intelligence isn't always the best measure of how successful one is. We all have that one super intelligent friend who works just hard enough to pay rent and buy weed. But that's another story

4. Lastly, I think the hesistance to accept a genetic intelligence difference between races is due largely to the ignorance of people who would use that information fact to justify their racist ideas. (I am NOT talking about all, or even most IQ fundamentalists, just the vocal few who would inevitably pop up). They would throw out the environmental/ social/ cultural factors that are invovled in intelligence not to mention success, ignore distribtuion within the population, outliers, etc. and brand a whole segment of society as inferior and unable to be helped.


One problem with twin studies, which many people seem to forget, is that all natural twins, even those separated at birth, share an environment -- the environment of the womb. Disentangling any congenital influences from environmental influences on any human characteristics, not only "intelligence", therefore requires very sophisticated experimental design and statistical analysis. I'm not convinced that experimenters have tackled this issue adequately yet.

Can anyone point to a twin study of intelligence which actually tries to account for the impact of a shared womb in its estimation of the relative impact of environmental and inherited influences?

Eric Turkheimer

Malcolm, I think you get the key issue exactly right. The paradox posed by dramatic increases in the average IQs of children rescued from poor environments contrasted with the high correlations between the IQs of children and their biological parents has been a theme of my research from the very beginning. In fact my first paper in behavior genetics was about this topic. It is linked at:




2 issues come to mind as I think about this. (and forgive me if they have been brought up, I wanted to get this in before my meeting)

The first is: The IQ test is not a proven fact. IQ is not a mathematical formula, or something that can be easily counted. To me, IQ seems more of a theory... not something you can base all this deep thought on.

The other is about the genetics side of this. Couldn't the genes of a person blueprint the IQ to rise with age? I was born with the genes to be of average hight, yet I was shorter then most until around the age of 20. Then I hit my growth spurt. Whats to say there isn't an IQ spurt that can happen.

IQ just seems like a poor stat to put so much emphasis on. It reminds me of a pitchers win total in baseball. A poor pitcher will never win 20 games, just as a great pitcher will not win only 7. However, because there are so many other variables that can come into play to effect that number, it should never be the only thing that determines a pitchers worth.

Dave F.

gbaked -- that baseball pitching analogy is a good one.


Oh, so there are twin studies showing that I.Q. is heritable? You mean, like the twin studies done by Cyril Burt?


Burt has so permanently discredited twin studies that at this point a reasonable person finds it impossible to take twin studies seriously. Now of course the obvious and obviously failed rebuttal goes: this represents a wild overreaction, since surely all the twin studies can't be fradulent.

Which fails for the obvious reason. When you've got two groups of researchers, and among 'em one groups has found it necessary to resort to flagrant scientific fraud, while the other hasn't, what does this tell you about the probable validity of their research?


"Oh, so there are twin studies showing that I.Q. is heritable? You mean, like the twin studies done by Cyril Burt?"

Er, no, rather the studies done by Richard Plomin and others since the 1970s. Believe me, many people would have loved to discredit them, but failed to do so.

This is as closed a case as it gets in the social sciences. Get over it.

Of course, if you chose to disbelieve any study that uses the only valid method to look into the question, it's not hard to insulate your beliefs.


In assessing the influence of genetics on intelligence, we must remember not to take for granted the assumption that are we are accurately measuring what we purport to measure. For instance, genes are largely static pieces of DNA. However, the expression of these genes is not static. DNA must be converted to RNA before proteins can be synthesized. The quantity of RNA that is produced and the amount of time that it lingers in the cells, both of which are more proximal determinants of the product of those genes, is typically determined by behavior and/or environment. This is an empirically supported principle known as epigenetics. Moreover, because genes code for proteins rather than behaviors, the application of those proteins are subject to interference from any number of chemicals present in the cellular environment. Thus the first fallacy of any attempt to link genetics with intelligence is to ignore the flexibility of genetic expression.
The second fallacy concerns our operationalization of intelligence as a stable construct. Any assessment of intelligence that can be heavily influenced by practice clearly does not measure an inflexible property. Thus, researchers who choose to study the role of genetics in intelligence are charged with a doubly difficult task: to use distal variables (DNA) to predict contextually specific outcomes (intelligence scores). This is the equivalent of using blood type to predict personality, as measured by people’s conversations with their hair stylists.
That some of these researchers do find a link is interesting, but it is not telling. This is because we do not know the set of mechanisms by which one or more gene-coded proteins influence performance on a particular set of assessments. Until there are specific hypotheses about why some proteins are linked with high intelligence scores or even, dare I tempt the most radical of evolutionary psychologists, why selective pressures for certain facets of intelligence were exerted differentially on various races of humans, then I remain skeptical of the current crop of research that links genetics and intelligence.

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