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Genetics and intelligence differences: five special findings (nature.com)
91 points by tokenadult on Sept 16, 2014 | hide | past | web | favorite | 81 comments

I never understood why the politically correct crowd happily accepts that athletic ability is heritable, yet when it comes to intelligence suddenly all bets are off.

As soon as we accept reality for what it is, we can begin adapting our societies and policies to maximize opportunities for individuals with the knowledge that our talents and limitations vary quite drastically.

It's not that I don't believe that intelligence is heritable. I do. It's more that I don't believe that it's all that important to be intelligent in order to be a good Human.

People have a natural attraction to those similar to them. In history, the over-emphasis of particular and possibly unimportant (who knows?) traits has often been the cause for wars, genocides and all sorts of other evils.

Further, I don't think that relative Human intelligence has all that much magnitude. That is - a 'really intelligent' Human is not all that different from a 'non-intelligent' one, taken in the context of other species. And, those non-intelligent ones may have particularly interesting genetics that make them important to the species, in other ways.

Humans have done pretty well as a species with lots of diversity. Why ruin a good thing? And, do you really want Humanity to be comprised of near clones?

Probably because the jobs traditionally done by the less intelligent are being shipped overseas or done by machines leaving these people in poor economic circumstances. Intelligent people would not have to be clones, smart people can be quite different from each other in terms of personality, areas of interest etc.

Conversations about it often don't go well.

All to often, people start using it as justification for income disparity, wealth disparity, minority crime rates and sometimes differences in economic development between different countries. Racism and classism aren't too far behind.

I'm reminded that it is no more noble to fool a person out of his money by outwitting him, than it is to bully him out of his money with superior strength. Being smarter isn't necessarily a moral justification for greater rewards.

Similarly, we rely on the economic system using prices as an information signalling mechanism; more valuable labour is priced up, and thus supply should follow. But if the valued labour is intelligent labour, and its supply is not easily increased, then there is less of a moral case for paying its suppliers more, for that attribute alone.

Although assuming it was true that intelligence was mostly based on genetics rather than quality of education (I don't have a strong view one way or the other) then we could use that knowledge to improve wealth inequality by filtering people into school systems with very different curriculum where they would learn the best way to add value with their ability level.

> assuming it was true that intelligence was mostly based on genetics rather than quality of education

I think the difference between these 2 opinions is their definition of intelligence.

> the politically correct crowd happily accepts ...

I don't think I've heard anyone serious say that there was no heredity of intelligence. Could you be more specific about who says what? Perhaps you are writing quickly, but these are imaginary statements from imaginary people.

>> I never understood why the politically correct crowd happily accepts that athletic ability is heritable, yet when it comes to intelligence suddenly all bets are off.

Because athletic ability is more recreational - you can say different people are good at sports, music, art, etc... there are nice alternatives. But it's not PC to imply anyone is inherently stupid. I phrase it that way because saying "inherently smarter" is OK on the surface, but the corollary is that someone else is inherently less smart. Being "PC" is all about not offending anyone.

The implications of intelligence are more touchy.

Outside of professional athletes, being good at soccer is not much more important than having blue eyes.

Intelligence, on the other hand, is an underpinning of modern life.

The only reason we acknowledge the heritability of wealth, another underpinning, is because it is by far too obvious to deny.

(Quite the reversal from the origin of the species!)

I'm not aware of any generalised test of athletic ability. The traits that make one good at archery will be different from those that make one a good sprinter. With intelligence we attempt to collapse it all down to one number and rate people as smart or dumb as a single metric.

Two points about this. First, a consensus developed over more than a hundred years of study requires a little more than an off-handed dismissal-- do you understand _why_ a general factor of intelligence is acknowledged by practically everyone who has studied the issue, or why it is impossible to devise a test that purports to measure cognitive ability but varies independently of that general factor?

Secondly, I gladly accept your reductio of a "general factor of fitness". If you restrict yourself to the range of world-class athletes, I grant that performance in archery will correlate negatively with performance in sprinting. This is just Berkson's paradox, or the "restriction of range" phenomenon. If you consider the entire population, however, I would be very surprised if a "general factor of fitness" didn't fall right out of a battery of athletic tests. In general, people who are faster than average will also be stronger than average and probably more dextrous too, and it makes sense to call that factor "physical fitness".

Intelligence and fitness are two very different things. Fitness has a lot to do with make up of muscle fibres in the body, fast twitch (anerobic) vs slow twitch (aerobic). This is why marathon runners and weight lifters have very different body types , training a lot in one discipline will make you worse at the other. Genetics plays a role in which type of muscle you can most easily develop.

Intelligence simply doesn't work the same way, learning to draw well won't make you worse at computer programming for example.

Yes, maxing out one dimension of performance may degrade it in another. This is just Berkson, again. My point is that along the entire range of variation, all reasonable measures of athletic performance are likely to be positively correlated. If you doubt this, consider the following thought experiment:

1. Pick an arbitrary athletic contest: 100m dash, bench press, obstacle course, marathon, whatever.

2. You pick a member of the population at random.

3. I pick a member of the German national football team at random.

4. If Joe Schmoe wins, I pay you a dollar. If Dieter Schmieter wins, you pay me a dollar.

5. Repeat until convinced.

Who do you think will win more money in the long run? Will the Germans tend to win because of their high general fitness, or will it be a toss-up because the Germans merely have "high soccer fitness" which does not help (or perhaps even disadvantages) them at non-soccer tasks?

That is what I mean when I speak of a "general factor of fitness". Over the whole range of population, people who do better at one athletic task will tend to do better at any other. If you take a sample from the population, measure their performances on whatever athletic tasks you choose, and drop the results into PCA, you will find one factor which is positively correlated with every test and explains, I'm guessing, at least 3/4 of the variance. What happens at the extreme tails is already acknowledged, and does not bear on this general point.

I tried to find data for non-elite-athletes taking something like the NFL combine and couldn't find anything, but there, at least, is a testable prediction for you.

My only point about a "general factor of fitness" was that I am unfazed by the comparison to IQ, because physical fitness is a perfectly reasonable concept that captures something real in the world. So too IQ. If you think the analogy is inapt, remember who brought it up :)

You're comparing a trained athlete against a person who is untrained. It is not surprising that fitness related tasks are very amenable to training in a way that is not quite so clear with intelligence. A more interesting comparison would be between a sedentary Dieter Schmieter who worked as a computer programmer (or a Dieter Schmieter who had trained purely for strength) and a random member of the population who was trained by Dieter Schmieter's coach for 10 years.

Amongst the general untrained population you will see very large variance between performance on different fitness tests. Lots of broadly built overweight people who are very strong despite never having done any weight training but can't walk up a flight of stairs without breaking a sweat and skinny people who can run well without much training but barely lift anything. So I would doubt that there would be a strong general factor for physical tasks.

Intelligence as a general topic is pretty hard for me to swallow. A lot of "intelligence" that we can test for is mathematical in nature and that can be learned. I'm pretty sure I could teach multiple-choice test taking.

Intelligence, I think, can broadly be defined as "the ability to score well on intelligence tests." The most common is supposedly correlated with freshman college survival. History is full of people who were considered "dull" as students but later shook the world in a way that means they had significant intellect.

It wouldn't be a problem except we sort people into piles and this is yet another sorting mechanism.

Would you mind elaborating on what you mean by "the politically correct crowd"?

You can probably guess it from context, but I had to look this up to be sure, so for the benefit of others: assortative mating is when you have kids with other people similar to you, rather than selecting mates randomly. In other words, in this case, people with high intelligence tend to marry other people with high intelligence, and people with low intelligence marry other people with low intelligence. This causes the variance in the distribution of intelligence to steadily increase, rather than everybody evening out over a few generations.

Assortative mating -- among other things -- was one of the "problems" identified by Charles Murray in his book Coming Apart as a cause of greater inequality in American society[1]. As people "stick to their own kind", there are fewer opportunities for both economic and cognitive mobility: in the past, when marriage was determined by other factors, it was more likely that a highly intelligent person might have children with a much less intelligent person. That's increasingly no longer the case.

[1] http://www.nytimes.com/2012/02/12/books/review/charles-murra...

Interesting, but assortative mating is not a new phenomenon in the history of mankind. If anything, its impact has probably decreased significantly over the past centuries and decades. This makes it more difficult to take such explanations for growing income inequality at face value.

Let's put it this way: a "meritocratic" society has made intelligence inextricable from wealth and power in a way that was not true 100 years ago or earlier. If you were very smart in 1900, whether you worked in a factory or ran the factory was determined by your family's wealth and influence, and that also determined your pool of available mates. So instead of having a society where people practice assortative mating based on non-hereditary factors (wealth and power) people are mating based on intelligence and passing it onto their children. (I suppose familiar wealth and power is "hereditary" to a degree, but not with the durability of intelligence.)

> Are the U.S. economy and society more meritocratic than they were 100 years ago?

I think this question is more fuzzy at the 100-year time scale than the 200, 500, or 1000-year scale. It seems fairly uncontroversial that "merit" (whether by pure intelligence or some other metric for skill) had little to do with your station in life in 1514.

> The value of specific cognitive skills varies over time.

True. We should be careful not to anachronistically apply meritocratic assumptions about intelligence to other eras where raw intelligence and mental flexibility was less important than domain knowledge and practiced skill. But can we safely say that the Information Age has put a premium on the skills of those with high intelligence, and the benefits accruing to those workers over the last 50-60 years has skewed the mating priorities of many?

> There is far more to capability than intelligence. For example, there are very smart people who, due to lack of emotional or interpersonal skills, don't produce much.

Also true. Murray is careful to note that when we speak about meritocracy or the hereditary impact of intelligence, we can really only generalize about groups -- it can be wildly inaccurate for individuals. Can we safely say that the Harvard Class of 2014 as a group will have greater economic value over the course of their lives than the Anytown Junior College Class of 2014?

> a "meritocratic" society has made intelligence inextricable from wealth and power in a way that was not true 100 years ago or earlier

An interesting hypothesis.

1) Are the U.S. economy and society more meritocratic than they were 100 years ago? I've seen research saying social mobility has decreased recently (it didn't say about over 100 years) and is lower than in Europe, for example. Also, at least some research says that access to higher education depends significantly on the wealth of your parents; elite universities (and others) have problems attracting and graduating poor, smart students.

2) The value of specific cognitive skills varies over time. If 100 years ago, you had great ability to translate problems into efficient data structures and logic, I'm not sure how much economic value you would have. 50 years from now, I'm not sure how many humans will be writing code.

3) There is far more to capability than intelligence. For example, there are very smart people who, due to lack of emotional or interpersonal skills, don't produce much.

Suppose US society was meritocratic, intelligence is highly hereditary, and assortative mating happens. Then you'd expect low social mobility - people will have the same intelligence, and hence the same income, as their parents.

And if a society values intelligence, they should encourage smarter people to reproduce and offer as much birth control as possible to less smart people. Following this line of reasoning and policy is sure to ignite all kinds of flame wars ;-)

The problem is that smart people tend to earn more, thus the children tend to cost them more both in terms of opportunity cost (hours away from work) and actual cost (more likely to consider things like private school as essential). To incentive them you would need to start giving already wealthy people quite significant tax breaks etc.

This is the silliest argument for why intelligence would be negatively correlated with number of children. FWIW, the original article very much did not assert that assertion; reproductive success (meaning having any children at all survive the parents) in fact may be positively correlated because the social status of richer/more intelligent parents translates to higher survival rates for their offspring.

Regardless, while the absolute cost of raising children may be higher for high-income families, the share of their total income that represents is much lower. Someone earning minimum wage will struggle to support even one child's basic food, clothing, and shelter; their counterpart making $1M a year could easily afford private school, childcare, and the best possible opportunities for a family of 3-4 children.

My comment doesn't argue that intelligence is negatively correlated with having children, it argues that it is difficult to incentivise intelligent people to have children. Although looking at figures for 2010 it does seem that there is a negative correlation between income and number of births (at least in the US).


Survival rate is unlikely to be highly correlated with income in a first world country because even the poor have relatively good healthcare. The group most likely to have children are those earning $10,000 per year or less, probably because at that income level the state will pay most of the costs associated with child rearing. In fact in some cases having children might make a person better off financially due to higher priority for welfare or public housing etc.

There is an interesting and much-neglected corollary to the heritability of intelligence, which is that we are part of the least intelligent generation of humanity that has ever lived.

This follows from the two conditions:

1) intelligence is at least somewhat heritable (empirically true, according to the article)


2) intelligence is positively correlated with reproductive success (plausible give humans seem to have been selected for it)

The conclusion follows from the way world population has exploded in the past 250 years, increasing roughly ten-fold in twenty or twenty-five generations. That increase equates to "zero selective pressure": basically anybody could breed successfully, and they did (including my ancestors, some of whom occupied the more stagnant and brackish depths of the gene pool...)

So up until 1750 or so intelligence was being selected for, generation after generation. After that time, there was no pressure and the many small effects that this article documents as underlying the heritability of intelligence (with no single gene showing as much as a 1% effect on the overall outcome) would happily carry us all on a random walk across the landscape, creating engineers in some parts and political partisans in others.

This realization makes particularly funny the various organizations that have at times promoted Nobelists etc as pinnacles of intelligence (William Shockly, inventor of the transistor, was heavily involved in this kind of thing). Nobelists are certainly bright, but it seems more likely you'd find the most intelligent people amongst still-extant stone age tribes, whose pre-industrial life-style would still subject them to selective pressures long released in the more-developed world.

> Nobelists are certainly bright, but it seems more likely you'd find the most intelligent people amongst still-extant stone age tribes, whose pre-industrial life-style would still subject them to selective pressures long released in the more-developed world.

This conclusion is only justifiable if (1) the population of "stone age tribes" and the part of the world where those selective pressures have been released (because people are indivisible units beyond a certain point), and (2) if intelligence was fully determined by genetics rather than merely having some heritable component.

If there are important environmental factors in intelligence to which modern technology can positively contributed, and there are a lot more people living with modern technology, then its quite possible that the mean, median, and max realized intelligence would be higher in the modern part of the world than in "stone age tribes", even if the latter have more genetic benefit from pro-intelligence selective pressure and thus a higher mean/median genetic intelligence capacity.

Stone age tribes select for more than just intelligence, as a smart guy you might be an advisor to the tribe leader but the tribe leader was most probably a medium smart very bulky fellow.

Reminds me of the recent study where Chimps beat humans in a simple strategy game.

Do you remember the name?

It's called eugenics and it's very bad. At the very least it suffers from this self-referential craziness that nearly guarantees bad results.

People are economically unproductive because the economy slowly gets more and more hostile to more and more people. Tyler Cowan and others call this problem "Zero Marginal Product Workers".

And it sure did ignite flame wars and the topic is not openly pursued anymore in scientific circles, regardless of how objective it might be.

Luckily we don't have to go there. Technology is going to be the great equalizer, and might end up offering you off-the-shelf intelligence upgrade (I'm talking about a time-frame of next 30-80 years).

So long as people have to compete in the workplace, then the resulting equilibrium from everybody having an artificially extended intelligence will probably be ( according to Arnold Kling ) like the Vickies and Thetes in Neal Stephenson's "The Diamond Age".

I've never read that, what is the resulting equilibrium?

Let's just say endings are not Stephenson's strong point.

I have yet to read it myself :)

Dr. Kling is using the book as a template/metaphor more than as a specific proscriptive. But I've seen this myself in the wind as various crises have held forth since 1973 ( when I was first old enough to ask questions about what was going on ).



> the topic is not openly pursued anymore in scientific circles


I'm not sure IQ is really that great in the grand scheme of things. Don't get me wrong it's good, but IQ wouldn't help us much if managed to screw the environment beyond our ability to repair it.

Also that article reeks of alarmism.

I first saw this concept in the context of intelligence in "The Bell Curve" by Richard J. Herrnstein and Charles Murray (1996). They suggested the process is accelerating dramatically with development of situations that make it easier for intelligent people to find each other: the movement of the population from the farm to cities, higher education, improved communications and less restricted travel. I would not be surprised if online dating sites are also playing a role. Once you start thinking about this in the context of genetics, matings and the potential for a survival advantage and increased quality of life leading to further segregation you wonder if this does not have the potential to eventually result in the development of a new species?! I would be interesting to know if the IQ "density" is significantly altered in certain communities in northern California, Boston, NY, etc. associated with industries selecting for high IQ workers. [Edit]Just amused myself thinking of the Silicon Valley crew as participants in a breeding experiment.

Species are not 'developed'. They come into being because of isolation and sufficient time passing.

Even all the breeding done with dogs has not resulted in speciation.

The time scales are vast and the degree of separation that a barrier such as 'intelligence' (for whatever definition you wish to employ) will provide will be insufficient to cause this to happen.

No Elois and Morlocks in our future through that avenue.

Think about it: if geographic separation and very long spans of time have not been enough then why would a mere trait be enough, we have plenty of examples of the former.

It's certainly possible if you factor in the social and geographic trends and take them to extreme conclusions. It's merely reproductive separation that is required. Whether this be due to geography, climate, mating calls or unattractive IQ isn't really of import. I'll agree that right now the barrier isn't sufficient enough, but I don't think that is what OP was saying (could be wrong).

That said, your point about the time scales is definitely on mark. It would take a long time and likely far more significant isolation than present (don't have numbers). Genetic engineering could speed that up substantially.

Of course social factors would likely prohibit any talk about separate species. From a pure biologist perspective there are many different animal species fully capable of reproducing but are speciated because their natural breeding behavior (or location) doesn't support interbreeding. Using the same measure/definition, one could objectively argue that uncontacted tribes and isolated peoples are a different 'species'.

I personally think scientists need to agree on some fundamental genetic/epigenetic (maybe even microbiomic) markers of speciation and move away from more subjective definitions. Reproductive potential makes sense when looking at speciation likelihood, but I am not sure it makes sense as a definition of different species.

Being able to interbreed is the very definition of a species.

So if two specimen are capable of breeding and the resulting offspring is not sterile they are considered to be of the same species.

Being from an un-contacted tribe has nothing whatsoever to do with speciation.

That's actually not the definition used in biology. Simple example: The entire genus Amphiprion (aka anemonefish) are speciated due to appearance and regional locality. They can and do interbreed when introduced into each others populations, and have fertile offspring that are mixed species. They are declared species due to their appearance, and their natural range's prevention of interbreeding. That said, there are areas where some ranges overlap and it's not uncommon that one species mates with another and has hybrid offspring.

Being genetically capable of interbreeding makes sense as a definition of speciation, but that is not how species are currently identified. Natural range, aesthetics, and more than that, whether or not they DO interbreed in the wild (vs physically/genetically capable) play a more significant role in determining species.

There are many 'hybrid' species in nature, which is what I feel warrants some revision, perhaps using genetic data to restructure many classifications as subspecies rather than independent species.

edit: Sorry, I think I may have misinterpreted what you said to some extent and think we generally agree. I will maintain that according to the classification methods described, people such as the Sentinelese, may well be considered a separate species to an unbiased observer using the same guidelines we apply to other animals due to slightly different physical characteristics and social/geographical reproductive isolation prevents the possibility of breeding with anyone outside of their group.

Being able to interbreed is the very definition of a species.

It isn't, and cannot be. The relation A interbreeds with B is not transitive.

Larus Gulls originated in Finland and spread west, evolving as they moved. Eventually some of them reached England. The Finnish ones breed with the Russian ones, Russian with Canadian, Canadian with English, but the English don't breed with the Finnish.


Sure. And that's just the spatial variety. There is also the temporal variety of that same phenomenon.

If a 3 million year old ancestor would suddenly pop out of nowhere into our midst chances are that we're far enough removed for interbreeding to be impossible and yet, we were able to breed at every intermediary stage just fine.

But for all normal everyday intents and purposes that definition holds up just fine. It's when you start to zoom in on what a species really is that it becomes more nebulous until you realize that all there is is individuals and their breeding capabilities.

Species are a phenomenon that is observed rather than one that actually exists.

Fascinating stuff.

It does not seem hard for me to contemplate the possibility that modern humans are primarily defined by our intelligence and that our closest relatives had less of it. Of course, as you point out, these developments occur over the course of perhaps hundreds of thousands of generations.It also seems pretty clear that catastrophes that dramatically reduce population sizes may also play a significant role in the process. Survivors of a catastrophe are likely to be geographically localized. The catastrophe eliminates gene pools and, by chance, selects for small subsets of the previously existing pool. Wash, rinse, repeat. And in a cosmic heartbeat....you have something different than what you started with.

Such catastrophes would have to do a better job of isolating people than they've been doing so far. Humanity is remarkably similar from a genetic perspective when taken as a species. I don't think your theory stands much chance unless you're willing to go interplanetary or inter-stellar. On planet earth we are remarkably mobile, to the point where if we lose all shipping ability and even knowledge of other civilizations that we'll likely re-discover all this from first principles within at most a few thousand years.

I was thinking "catastrophe" as in a wipe out the dinosaurs asteroid hit or a global pandemic that takes out 95% of the population (think Ebola)or an EMP event that results civilization collapse, etc. So if Silicon Valley residents are the only survivors (god help us :-)and there is a higher IQ density there than other locations and if IQ is really significantly genetic, then the average IQ of humans has increased and can be maintained in the population. Other pockets of survivors would have an IQ density similar to that present in the general population existing before the catastrophe and based on our hypothetical case, lower than that in Silicon Valley. It is the geographic isolation and geographic concentration of a particular genetic trait that makes this type of selection possible.

What makes you feel that the average IQ of Silicon Valley might be higher than say Beijing, Tokyo, Adelaide or Moscow?

Nothing. I was just using an example of which I had some familiarity. In the context of this hypothetical thread, it is interesting to note that there is apparently some scientific data suggesting that Asians have a slightly higher IQ than other races. Not being an expert I can't readily provide the references. The other reason for using Silicon Valley as an example is that the theoretical we are discussing requires a survivor population that has a higher IQ density than the average population. The larger the sampling the closer the IQ density approaches average. Although I guess the argument would still hold for a city or country. I was just thinking that the difference in IQ density between Silicon Vally and California as a whole might be 20 points while the difference between China and the US might be 2 points.

Unfortunately for us, it seems that the more 'evolved' we get, the smaller our brains get:


Having now learned the terminology, assortative mating could indeed lead to speciation in the general case; it's just a special case of sexual selection. I find it highly unlikely that that will happen with human intelligence, though (despite the fact that it's been used in fiction more than once). The reason is that there's a limit to how big the variance can get- it doesn't grow forever, it grows until limited by other factors (i.e., there are only so many intelligence-promoting alleles that you can possibly have).

It would take intentional segregation to cut off all gene flow between the upper and lower halves of the intelligence Bell curve, thus allowing other differences to pile up between the populations, to cause speciation. And as noted elsethread, that's called eugenics and generally frowned upon in polite society.

> The reason is that there's a limit to how big the variance can get- it doesn't grow forever, it grows until limited by other factors (i.e., there are only so many intelligence-promoting alleles that you can possibly have).

What makes you think that? You could say the same thing about seed size in plants, but comparing modern corn kernels to wild type seeds provides a clear counterexample.

You should look at the type of stuff they've done in plants and animals. Here's a paper on the selective breeding of fruit flies for flight speed. The results are astounding:

"The mean apparent flying speed of both lines increased from approximately 2 to 170 cm/sec and continued to respond at diminishing rates, without reaching a plateau, for 100 generations. Competitive fitness tests in generations 50 and 85 showed minimal or no fitness loss in selected lines compared to controls."


Interestingly, the current mating and segregation trends, to the extent they exist, appear to be completely "natural" and lacking in premeditation. Can't help but wonder if modern humans are not the result of a process that left the Neanderthals ( pre-modern humans, whoever they were) behind. I'm no expert, but I don't think a complete lack of gene flow between groups is thought to be required for the process of speciation.

Neanderthals at least had bigger brains than modern humans.

I would suspect that physical looks/features would throw a wrench into this - or at least correct things a bit.

I don't follow. How would that affect this phenomenon? Given that the cited correlation refers strictly to intelligence, looks (and for that matter, all other factors) are presumably already accounted for.

It was more a response to the parent comment. I was suggesting that an intelligent person may choose a mate that's less intelligent because they're prettier which would help resist some of the divergence.

They mention assortative mating is greater for intelligence compared to physical aspects like height and weight, but 'prettiness' is a more subjective harder to quantify measure that I would guess plays a larger role in mate selection than just height and weight. This is ignoring the fact that height and weight are probably opposite anyway (women wanting taller men, men wanting shorter women) - so there are some issues there too.

yep, until gap becomes too big so the species divergence begins as physical looks/features play role for both processes - help keep a species together as well as to help distinguish between subspecies once the divergence has started thus speeding up the divergence.

From a cursory glance at this post, I don't see how your conclusion follows. I'd believe it if I saw the model and some data that supports it. It depends on how populations along the intelligence distribution reproduce, and what the variance of intelligence is of offspring along the continuum. If everyone reproduces at the same rate, and the intelligence variance of offspring is constant across the population, then I would expect the intelligence distribution of the overall population to remain the same. It seems like, given those constraints (which may or may not be true), the variance would remain the same--neither evening out nor diverging.

Let me know if I'm mistaken...honestly I've only read part of the article and I only have a lay understanding of this stuff.

Would someone decode what Nature means by "open" and "expert review"? What is "open" about it? Is this settled science, one person's hypothesis, or something in between?

1. Open = free (no subscription required)

2. Expert review = exactly what it sounds like (as opposed to original research)

3. Something in-between

Is it really 'something in-between'? This is https://en.wikipedia.org/wiki/Robert_Plomin - if there's a greater living behavioral geneticist, his name escapes me.

> Is it really 'something in-between'? This is https://en.wikipedia.org/wiki/Robert_Plomin - if there's a greater living behavioral geneticist, his name escapes me.

That is a valuable piece of information for us lay people. Do non-geneticists studying the issue generally agree with him?

>> Is this settled science, one person's hypothesis, or something in between?

> 3. Something in-between

Much appreciated (all of your answers). If someone has knowledge of where this falls on the continuum of #3, it would help those of us outside the field understand how much credibility we should give to this article.

I can't speak for the GCTA method, but the five main findings discussed in the review have all been known within the field for years: this is a review, rather than a research article.

If these findings are surprising to you, it is because there is probably no greater gap between lay and expert opinion than on the subject of intelligence. The psychological study of intelligence has a poor reputation among the lay public primarily due to the perception that it might support unsavory political conclusions. Hence, psychometric research must be intrinsically flawed crackpottery. In truth, the correlations between IQ and various life outcomes exceed practically any other effect observed in social science. Further, we have as much reason as we ever could have in social science--from a variety of sources all pointing in the same direction--to suspect that the causal arrow points from intelligence to good outcomes.

I encourage you to look into the issue for yourself, but my synopsis is that the picture one gets from the literature is unrecognizably different from the picture one gets from non-specialist media.


Thanks. If I may ask, are you a member of the lay public or do you have some expertise in the field (certainly you know more than I do!)?

> If these findings are surprising to you

Not knowing much about the field, I didn't have many expectations.

What sources and material would you recommend for a layman interested in understanding the state of psychometric research?

It's kind of trite and obvious by now, but can we please kill the "Everyone gets what they deserve" line of thinking?

The idea that "they deserve whatever they can get" is one of the criticisms of modern UK/US culture made by Michael Young who actually coined the term in his satirical book The Rise of the Meritocracy:


[Edit: I don't know about the US but here in the UK it is fairly common to define "merit" in ways that don't actually seem to include "performance" - though I think this is a far bigger problem in the public sector than the private].

This is basically the "just world" fallacy writ large, right?

Q: What is intelligence? A: Thing that is measured with intelligence tests.

Q: What are intelligence tests? A: Things that measure intelligence.

This pair of rhetorical questions actually has a non-rhetorical answer, and it is far more interesting (though less precious) than the one implied here.

This being the internet, the serious answer is a mouseclick away: http://en.wikipedia.org/wiki/G_factor_%28psychometrics%29

It is more correctly circular reasoning. The psychometric measure g does not break this circle at all. I will never believe in "intelligence tests" until this circular reasoning can be broken.

Why do you think we observe the positive manifold, then?

I do not know why the positive manifold is as it is. But it still seems like it is a precise measure of an inaccuracy.

What I am getting at in a roundabout way is that I cannot find any credible definition of intelligence that is not dependent on the these tests. If intelligence were able to measured some other way that corroborated these tests, then I will be more likely to believe them.

Thanks for the interesting comments posted while I was watching my sons play soccer this evening. To answer some questions that came up in various subthreads, yes, both Robert Plomin and Ian Deary are mainstream researchers on the behavior genetics of human intelligence, the authors of well regarded textbooks (Plomin), popular books (both), and primary research articles (both) on various related topics. Their joint point of view as expressed in the review article published today is not the exact point of view of all researchers in the field, but I thought it would do as a discussion-starter here on Hacker News.

A crucial detail (Deary and Plomin would both agree about this, but it hasn't come up in the discussion here yet) is that heritablity has NOTHING to do with modifiability. It is quite possible in principle that a novel environmental intervention might be discovered that could boost most people's intelligence. It is even possible that the most effective intervention might have a gene-environment (G × E) interaction such that the intervention would most help people with lowest IQ, and least help people who already have high IQs. No such intervention that human beings can direct purposefully has yet been found, but it is clear from the Flynn effect[1] that something in the environment can have powerful effects in raising average IQ levels of whole countries, as has happened in the developed world throughout the last century (for as long as IQ tests have been around).

It is correct that people marry and have children on bases other than just shared level of intelligence. (But living in the same town, and completing higher education at similar ages, and pursuing compatible occupations for marriage, etc. is correlated with IQ.) It is still far too early to say how rapidly human populations might see noticeable effects from assortative mating by IQ. It is reasonably clear that often-feared dysenic trends probably are NOT happening--the lowest-IQ people in the world population don't reproduce at all, and high-IQ people actually have reasonable numbers of children to replicate their genes. In any event, the favorable environmental trends have SWAMPED whatever genetic trends are going on for IQ in the whole human population, and people are getting smarter all over the world, according to the research on the Flynn effect.

It is still a hard problem to identify anything at all meaningful and replicable about how gene differences influence IQ differences, even though it is now settled wisdom that they do. Human IQ, as the article says, is influenced by MANY genes, and many of those genes interact with one another in ways that are not understood at all yet.

[1] https://www.ted.com/talks/james_flynn_why_our_iq_levels_are_...


Plominism: The Christian heresy that salvation is neither by faith nor by works, but 50% hereditary and 50% based on non-shared environment


So, it seems to follow that one could take a bunch of fertilized embryos, measure the genome-wide polygenic score (GPS) of each embryo, then select only the best one.

The only thing missing is that the genome-wide polygenic score (GPS) for intelligence has yet to be discovered.

Unfortunately, even when something like this is possible, it would probably be made illegal even though it would surely be a positive thing for humanity.

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