In which a group of graying eternal amateurs discuss their passions, interests and obsessions, among them: movies, art, politics, evolutionary biology, taxes, writing, computers, these kids these days, and lousy educations.

E-Mail Donald
Demographer, recovering sociologist, and arts buff

E-Mail Fenster
College administrator and arts buff

E-Mail Francis
Architectural historian and arts buff

E-Mail Friedrich
Entrepreneur and arts buff
E-Mail Michael
Media flunky and arts buff

We assume it's OK to quote emailers by name.

Try Advanced Search

  1. Another Technical Note
  2. La Ligne Maginot
  3. Actress Notes
  4. Technical Day
  5. Peripheral Explanation
  6. More Immigration Links
  7. Another Graphic Detournement
  8. Peripheral Artists (5): Mikhail Vrubel
  9. Illegal Update

Sasha Castel
AC Douglas
Out of Lascaux
The Ambler
Modern Art Notes
Cranky Professor
Mike Snider on Poetry
Silliman on Poetry
Felix Salmon
Polly Frost
Polly and Ray's Forum
Stumbling Tongue
Brian's Culture Blog
Banana Oil
Scourge of Modernism
Visible Darkness
Thomas Hobbs
Blog Lodge
Leibman Theory
Goliard Dream
Third Level Digression
Here Inside
My Stupid Dog
W.J. Duquette

Politics, Education, and Economics Blogs
Andrew Sullivan
The Corner at National Review
Steve Sailer
Joanne Jacobs
Natalie Solent
A Libertarian Parent in the Countryside
Rational Parenting
Colby Cosh
View from the Right
Pejman Pundit
God of the Machine
One Good Turn
Liberty Log
Daily Pundit
Catallaxy Files
Greatest Jeneration
Glenn Frazier
Jane Galt
Jim Miller
Limbic Nutrition
Innocents Abroad
Chicago Boyz
James Lileks
Cybrarian at Large
Hello Bloggy!
Setting the World to Rights
Travelling Shoes

Redwood Dragon
The Invisible Hand
Daze Reader
Lynn Sislo
The Fat Guy
Jon Walz


Our Last 50 Referrers

« American Splendor | Main | Elsewhere »

September 02, 2003

Genetics, Environment and IQ


I’ve been reading a lot recently about environmental impacts on IQ, and I must admit it is kind of intriguing. (I should warn you before I go any further, however, that I’m about to link up a bunch of disparate facts here, and may well end up adding two and two and getting twenty-two. Is your seat belt buckled? Here we go.)

There are several paradoxes about the relationship between nature and nurture in the IQ field. On the one hand, IQ clearly has a major genetic element to it. Recent measurements suggest that it appears that variations in the IQ of late adolescents are about 75% explainable in terms of their parents’ IQs.

That’s a pretty good theory, right? I mean, few cause-effect explanations in the world of the social sciences are remotely that strong. Case closed—your genes are 75% or more of your fate, intellectually speaking.

Ah, but not so fast, buster. This measurement of heritability rises with age. The variations in the IQ of younger children are less explainable in terms of their parent’s IQ than those of late adolescents. Adult IQs are even more explainable in terms of parental IQ than are those of late adolescents. The environment seems to affect IQ more in the case of children than of adults, who appear to “revert” to their genetic “mean.” (The intellectual impacts of programs like “Head Start,” for example, are very noticeable in the first few years of school but vanish by the end of elementary school.) The main explanation I’ve come across in books like Matt Ridley's "Nature via Nurture" is that what is being inherited is perhaps not so much a once-and-for-all serving of smarts, but rather a mixture of smarts and the taste for either using them or ignoring them. Whatever your serving of smarts, it is possible that if you spend a lot of time solving complex equations, playing chess and doing crossword puzzles that your IQ will measure higher than if you sit on the couch watching TV and burping. This explains why the heritability of IQ would go up through your life, because the older you get the more control you have over your time, and the more your environment will come to fit your “taste” either for or against intellectually stimulating pursuits.

Well that’s better, but not yet good enough. There are still more tricky facts that need explaining. It turns out that society’s average IQ is rising with the passage of time, at a speed far greater than would seem explainable purely by genetics. Between 1950 and 2000, for example, the average IQ of draftees into the Dutch army rose by 20 IQ points, (i.e., from something like an average of 100 to something like 120). This translates into 1.5 standard deviation improvement in only a few generations. The obvious explanation would be that the environment became more encouraging of the use of smarts—or at least the type of smarts measured by IQ tests—but remember, the standard model says that only 25% of IQ variation is explainable by environment. Environments in the Netherlands would have had to improve enormously over that fifty years time span to explain such a large rise. (One estimate is that the IQ-enhancing features of everyone’s environment in 2000 would have had to be as good as the environment of the very top 1% in 1950). How likely is that?

Well, I came across a paper on the Internet by William T. Dickens of The Brookings Institution and by James R. Flynn of the University of Otago, which you can read here, which describes a mathematical model of genetic/environmental interaction in IQ over time that claims to explain all of these paradoxes. If I’m reading it correctly, this paper espouses the following notions:

· That environment and genetics mutually impact each other, with certain environments raising IQs—at least in the short term—and with higher-IQ people having a more or less automatic tendency to seek out more stimulating environments.

· That because of such mutual impacts, measures of genetic heritability of IQ will be overstated, and measures of environmental factors will be correspondingly understated, or masked.

· That environmental effects will also look less powerful than they are because they include positive and negative factors, most of which cancel each other out. But when a long-lasting element of the environment affecting IQ isn’t balanced by a similar long-lasting element that cancels it out, even a fairly small “unbalanced” environmental factor can raise or lower average IQs significantly over time.

· That being around more intelligent people is automatically stimulating to your IQ. This can create a social multiplier effect that raises everyone’s IQ in a group. Presumably this works the same on the negative side if you hang out with less intelligent people.

· That environmental effects raise (or lower) IQs via a one time bump (or dip) that happens in a fairly short time after exposure to a new environment, generally within a year. (This is observable with adopted children.) The resulting enhanced or diminished IQ, however, will gradually decay over a longer time span (as with the “Head Start” kids) unless greater amounts of environmental stimulus are then applied.

· That environmental enrichment in childhood, therefore, can only have a long term impact on people by reinforcing their “taste” for cognitively challenging environments, rather than by directly impacting their intelligence in later years. If you want to raise adult IQs, you would need to enrich adult environments.

Obviously, this is simply a mathematical model, which like all such models simply reads back to you the assumptions you built into it in a sort of mathematicized form. Still, it is suggestive, particularly when combined with an article I read recently in the September 2003 issue of Scientific American. This is “Brain, Repair Yourself” by Fred H. Gage, who is Adler Professor in the Laboratory of Genetics at the Salk Institute for Biological Studies in San Diego.

Professor Gage’s article focuses on neurogenesis, which is the process by which new brain cells, or neurons, are created throughout life (or, at least, are created throughout life in healthy, happy brains—more on that later.) It appears that these new brain cells play a role in the brain’s intellectual processes. The new cells form in the ventricles in the forebrain and in the hippocampus. The forebrain cells migrate to the olfactory bulbs for reasons not understood, but the other neurons find a home in the hippocampus, a brain structure that is crucial for learning new information. Perhaps not surprisingly, therefore, is that the rate of neurogenesis is strongly affected by the brain’s interaction with its environment. As Professor Gage notes:

One of the most striking aspects of neurogenesis is that experience can regulate the rate of cell division, the survival of newborn neurons, and their ability to integrate into the existing neural circuitry. Adult mice that are moved from a rather sterile, simple cage to a larger one that has running wheels and toys, for instance, will experience a significant increase in neurogenesis.

The flip side of such stimulus may be chronic stress, which seems to have a link via the suppression of neurogenesis to emotional depression. Again, according to Professor Gage:

Chronic stress is believed to be the most important causal factor in depression aside from a genetic predisposition to the disorder, and stress is known to restrict the number of newly generated neurons in the hippocampus…Many currently available drugs for treating depression, such as Prozac, augment neurogenesis in experimental animals. Interestingly, most of these drugs take up to one month to elevate mood—the same time required for neurogenesis. This finding has led to the hypothesis that depression is in part caused by a decrease in neurogenesis in the hippocampus. Recent clinical imaging studies have confirmed that the hippocampus is shrunken in chronically depressed patients.

It would be very interesting to find out if chronic stress and depression correlate with decreased IQ, no? In any event (and here I’m about to make another Superman-style leap), I recall a study from Britain which showed that hierarchical position in the civil service correlated quite nicely with stress as indicated by heart disease. Being the low man on the totem pole in such a hierarchical situation was far more dangerous to your health than being significantly overweight, eating a terrible diet, or even smoking.

I can only wonder if low status-induced chronic stress is not the sort of “unbalanced” environmental factor that could cause the type of long-term shift in IQ that the mathematical model described above suggests is possible.

You may have been wondering when a discussion of IQ such as this one was going to get around to the issues described in “The Bell Curve.” Well, we made it. All of this strikes me as a hypothesis that might explain persistent IQ differences between low- and high-status groups in society. If this is true, it would suggest (1) the enormous social importance of creating highly enriching environments, both for children and for adults, and (2) why it is important to avoid the creation of massive hierarchical social structures, in which large numbers of people will always suffer low status.

In short, I have a hypothesis that, by a strange coincidence, corresponds with Friedrich von Blowhard’s prescription for a better world: improved (more intellectually stimulative) schooling, self-employment (away from hierarchical organizations) and more stimulative aesthetics. Where does the aesthetics come in, you ask? I defer to Professor Gage:

A final consideration is the environment in which we live and work. More and more experimental evidence indicates that environment can affect the wiring of the brain. This opens up vistas of possibility for architecture and suggests that future homes and offices might be designed with an eye toward how they might provide an enriched environment for enhancing brain function.

More stimulative environments, by the way, won't necessarily be loaded with TV monitors and flashing lights. In the case of mice, an enriched environment is more along the lines of a nice cage with nice toys and opportunities for physical exercise--an environment that the scientist who discovered neurogenesis described as far less intellectually stressful than one a typical fieldmouse encounters. In other words, aesthetically speaking, the type of stimulation may be more important than the sheer level of stimulation.

Looking forward to hearing any thoughts or reactions you have of these speculations.



posted by Friedrich at September 2, 2003


It's amazing, with all the increased stress in the world over the past 50 years, that the average IQ score in the Dutch army didn't DECLINE 20 points, instead of increasing!

This is also making me think I need to build a nice cage with nice toys for one of my IQ-challenged coworkers. Heck, it sounds pretty good to me.

Posted by: annette on September 2, 2003 10:01 PM

The Flynn Effect (named after the good doctor who's paper you link) has also been shown to have a lot to do with increased nutrition, especially the availability of calories.

The pig in the poke of the whole matter is that the standard deviations between racial groups has stayed the same, even as the average has risen for all groups (and every so often they re-norm IQ so that the average stays a 100 now is smarter than a 100 fifty years ago).

Steve Sailer would have a lot more to say about this...Steve?

Posted by: David Mercer on September 2, 2003 11:59 PM

I always find myself thinking dopey thoughts when conversations about IQ come up -- probably a telltale sign of something or other. But, for instance: is a higher IQ always more desirable than a lower one? I've certainly known some miserable high-IQ types, and some happy and industrious modest-IQ ones. Come to think of it, I wonder if anyone's done any studies correlating (or attempting to) IQ and happiness, or satisfaction, or contentedness. My own hunch is that higher-IQ types often have a harder time of it in life than moderate-IQ types do.

Steve? Razib?

Posted by: Michael Blowhard on September 3, 2003 12:37 AM

M. Blowhard - being bright is, generally, a good thing for one's happiness and mental health.

Bright people, after all, can solve problems, understand the causes of slings and arrows or at least see them as part of the big picture.

That or the IQ depressing affect of mental illness skews the numbers. I've heard both stories.

I, however, need a big cage with shiny things and a wheel. Canyon Ranch might do.

Posted by: j.c. on September 3, 2003 01:04 AM


I don't know, you may be right, but that study of British civil servants seemed to strongly suggest that people are more content with their "lot" at the top of the hierarchy--and in contemporary society, those who are at the top are likelier to be those with higher IQs. I've also been reading about life in high-poverty neighborhoods, where average IQs are on the low side--they don't sound like paradises of contentment either. To say nothing of life in prison, prisoners being a notoriously low-IQ population.

In any event, my view of a happier organization of society is one that assidulously avoids creating situations where people have to live at the bottom of a social hierarchy. For all the difficulties associated with what Emerson called dignified independence, I think long term it's got a lot to recommend it.

Posted by: Friedrich von Blowhard on September 3, 2003 01:06 AM

Speaking of stress: If one is a baboon, the worst possible type of stress is the stress of being picked on and unable to fight back, followed closely by the stress of trying to hold your high status, a state which is followed by a lifetime of being picked on by those who have not forgotten what a rotton bastard baboon you were during your glory days.

The lesson seems to be that the worst thing that can happen to a baboon is to be a low-status ape all his life, then second worse is to make it to the top.

And guess who fathers a significant portion of the baby baboons? Middle status baboons who make hay while the alpha is busy showing off by brutalizing the low-status. Another lesson, I think.

Posted by: j.c. on September 3, 2003 01:08 AM

J.C. -- I suspect that with your second comment above you and I wind up saying more or less the same thing: that the extreme high end (like the extreme low end) can be a bummer. That clearly holds with status; my guess is that it might also hold with IQ.

Bright people often do OK for themselves. Ultrabright people, at least in my experience, often make a terrible hash of life. (Or, in some cases, just back out of it entirely.) They can see connections and solve problems, but maybe they don't have the character it takes to act on what they see and know, or maybe they see much too much in the way of possibilities and lose track of what might be in their own best interest, or maybe they just find themselves perplexed by (and then buffalo'd by) people for whom life is a simpler thing. (And then wind up in a spiral of resentment and self-hate: why should I be the loser here when I'm clearly the smarter person?)

I'm just sounding off here, I know, but I do wonder sometimes why this aspect of high-IQ life seems so seldom discussed.

FvB -- Ooh, I knew you'd come back with the prison/low-IQ thing. I'm assuming adequate IQ, of course -- hard to imagine many circumstances where a really, really low IQ would be a boon to anyone. But I've always wondered about the higher-IQs-means-top-of-the-heap generalization. Happy to accept that there's a rough correlation -- scientists and engineers and doctors are very bright and do well for themselves, thankyouveddymuch. But in what sense are they the real top of the heap? They're almost all working for someone else. And who's that person? In my experience, often someone who's bright-to-very-bright, but not brilliant-brilliant. The kind of toughness, shrewdness, opportunism, and steeliness that being a real top-of-the-heap person demands -- well, in my experience a super-high IQ not only rarely goes with that combo, it would probably interfere with such a creature's functioning. Have you seen any discussion of this -- ie., how the high-IQ-equals-success thing overlaps (if at all) with the fact that the alpha dog often isn't the brightest of the pack?

I also find myself thinking that there are lots of lifestyles, let alone lots of jobs, that are pretty swell (and that need living and doing) but that don't demand tons of spare IQ points. If we gave everyone in those lives and positions an injection of, say, 10 extra IQ points, I wonder what the result would be. I'm guessing disruption, restlessness and confusion.

But I'm heading off on my own rants and missing the point of your posting. Still, do you think higher-IQ always equals better? I wonder myself.

Posted by: Michael Blowhard on September 3, 2003 01:43 AM

Oops, I notice my tone got away from there -- apologies. I just mean to be a little mischievous at the expense not of you but of the maniacs, who seem to be numerous online, who seem to think high IQs are the be-all and end-all, as well as the solution to everything.

Posted by: Michael Blowhard on September 3, 2003 08:40 AM

David Mercer: The Flynn Effect (named after the good doctor who's paper you link) has also been shown to have a lot to do with increased nutrition, especially the availability of calories.

I wonder if lead, or other toxic chemicals that affect the brain, are less prevalent in the environment also.

Posted by: snore on September 3, 2003 09:57 AM

Not to speak for the Blowhards, but I think their positions can be reconciled. Friedrich argues that, all things being equal, the more IQ points the better. This seems indisputable: IQ correlates significantly with attractive outcomes like making money and staying out of jail. Michael replies that all things are not equal, and suggests that extremely high IQs may correlate negatively with the temperament required for worldly success. This too may be true, but Michael's evidence for it is anecdotal, which may be unavoidable since he is talking about a tiny slice at the far right of the distribution curve. But I suspect Michael is right too: there are other factors for worldly success that are more important, but less well-understood, than IQ, and their importance is magnified when you reach a certain level of cognitive ability. We tend to overrate the significance of what we understand.

Posted by: Aaron Haspel on September 3, 2003 10:57 AM

Aaron's nailed it with his usual precision. Thanks for clearing away my mental fog. Now back to the actual topic of the posting ...

Posted by: Michael Blowhard on September 3, 2003 11:21 AM

Perhaps instead of saying handsome is as handsome does, we should start clucking and frowning and saying "High IQ is as high IQ does."

Meanwhile, I'll continue to hold my hillbilly view that any meaningful measure of IQ assessed problem solving ability, and people who continue to have trouble solving problems are not, perhaps, as bright as they like to hope or can demonstrate in carefully controlled conditions.

At this point, except in a the few intelligent discussions (such as blowhard's), a high IQ or an ADD or "autism" diagnosis is a free pass. It seems as though the study of intelligence is now devoted to proving that anyone who's a tad awkward must be too bright for the rest of us. Sort of like the outdated ideal of the delicate female who's too sensitive for the ugliness of real life.

Posted by: j.c. on September 3, 2003 03:42 PM

I happen to know some of the Dutch scientists who have compared the average scores on IQ-tests through the years. The research started out to compare the scores of fathers with the scores of the sons, but went in several other directions after that.

Part of their current theory to explain the effect is that the rise in IQ has a lot to do with the rise in food quality. Currently the Dutch are the tallest people on average in the world, which certainly has to do with the food. [Like: lots of dairy products].

So, they reckon the circumstances under which the brain of the Dutch can develop in the womb and later, have been getting better from generation to generation.

Problem is, how can this be tested? Or proven?

Posted by: ijsbrand on September 3, 2003 07:45 PM

About Dutch congenital development - how about the WWII starvation years? any children born then probably had worse nutrition than their parents or their children.

Posted by: clew on September 3, 2003 11:29 PM

Hmm, diet and IQ ... Junk food ... Fat kids ... Has anyone got any thoughts or facts about obesity and IQ?

Posted by: Michael Blowhard on September 4, 2003 08:00 AM

About Dutch congenital development - how about the WWII starvation years? any children born then probably had worse nutrition than their parents or their children.

There was only real starvation in the four big cities, and only during the hungerwinter of 1944-45. The south of the Netherlands - below the main rivers - was already liberated then, and in the rest of the countries food was rationed, but not a real problem.

There's a NGO in the Netherlands nowadays advising the public about good food called the Hartstichting [Heart foundation]. Historians joke that the only time the Dutch population really followed the guidelines of this Hartstichting during the hungerwinter. Which may be an exageration, but not a big one.

Posted by: ijsbrand on September 4, 2003 08:24 AM

Stress is a word widely thrown around in today's society and something which is grossly rejected by older generations. So why is it that IQ is on the rise yet previous generations suffered less from stress - linked with reduced neurogenesis? It just goes to show that enriched environments and easier access to, not to mention vastly improved, education system can work wonders for IQ. But it also reinforces the dangers of stress and highlights the need for more effective stress management. Maybe these 'enriched' environments are linked with stress, for example the pressure to do well in exams and go onto further education.

Posted by: Katy Bovis on October 1, 2003 10:17 AM

My post refers back to "Bright people often do OK for themselves. Ultrabright people, at least in my experience, often make a terrible hash of life."

I wish you guys could ask my dad about this--but he died- His IQ was 180- and he was miserable and definately made a terrible hash of life"-- I always wanted to ask him-- how do you feel about having such a High IQ- do you think its the reason why you are so socially disfuntional and why you drink so much??? But of course I never felt it was an appropriate question. I always wonder-- was it nature or nurture or his incredibly high IQ or just plain bad luck that caused him so many problems?

If someone does come across some research about IQ and happiness/social disfunction-- email me -thanks.

Posted by: tommy on January 30, 2004 08:55 PM

i believe that higher IQ general makes people unhappy because they see alot of the bad things that lower IQ people don't. they have more to think about and have thoughts and dreams farther reaching that become unfulfilled. another effect is that the more intelligent kids normaly have various troubles in school getting picked on for their thirst for knowlage. lower IQ people also have trouble in society because there iability to provide a service to society causing them to be unhappy as well. however the moderate people normaly do not get picked on as much for being smart or stupid. and since that is where most people lie they make the majority and have more people like them. they do not crave knowlage but they do not shun it. they enjoy things because there is more for them to enjoy since society is built for the common man. i consider myself to be on the line between the intelligent and the common man always asking why but able to enjoy the simpler things in life. i crave knowlage but i know how to enjoy myself in society. i am the straight A student who took all the hard classes but chooses not to go to college but to enjoy a middle class life following in my fathers foot steps.

Posted by: chris on April 19, 2004 01:37 PM

Hi i am in middle school and i have a very high IQ, and I would like to say that we don't make a mess of life, others do it for us lots of getting picked on and teased, sometimes nobody except the teacher understands what you write what you write is too intelligent. I would imagine tat the same thing goes on with adults teasing, not getting promoted as fast because ofresentment and the public not being able to understand what you are saying etc.

Posted by: stuart on April 29, 2004 05:07 PM

If you have the will and force of pesonality strong enough to get and stay super-smart then you don't really care as much about what others think of you.

Posted by: stuart on April 29, 2004 05:10 PM

Post a comment

Email Address:



Remember your info?