Let's be intelligent about intelligence

A lot of confusion reins over assertions about whether a physical or even behavioral trait is  'genetic'. There are several reasons for this.  One is the difference between mechanism and variation. Every human trait is genetic in the first sense: an organism develops from a fertilized egg because it has genes, and without its genes it could do or even be nothing.  So every trait is 'genetic' in the mechanism sense. But the other meaning of 'genetic' has to do with variation, and that is where the difficulty and often the contention lies.  The assertion that a trait is 'genetic' in this sense means that some people with a trait, or a particular trait measure, have it because of some particular genotype. That is, we all differ in the trait because of causal genetic differences.  Identifying genetic mechanisms or demonstrating that genetic variation is responsible for variation in a trait are genuine challenges.

Searching for genetic mechanisms responsible for, say, heart disease is one of those challenges.  It's difficult scientifically, but unlike with some other traits, the scientific question isn't politically loaded. Many people fervently want to stress the genetic role in intelligence, for example, and it's often for thinly disguised racist or elitist reasons.  A common response to almost any suggestion that an individual's intelligence might not be inborn, due to variants in his/her inherited genotype (meaning built-into the person's DNA sequence), is an accusation that the person is in denial of reality (but see our Dec 14 post about genetics and dialectics).  But who is really denying reality in such cases?  In our view, it is those who misperceive or misuse measures like heritability and have deep, emotional commitment to inborn destiny.

And, again, it's pretty clear that just slightly beneath the surface is often a racist or other discriminatory agenda: "let's identify 'them' and do something about it, to 'improve' them or prevent them from harming everybody else" (Trump's throw the Muslims out campaign, or the reluctance to invest 'our' resources in groups with inferior IQ, or in the worst case, eliminate them). If it's important to understand why people behave as they do (intelligence being just one aspect of behavior; there are of course many others), the argument goes, then one needs to know if it's genetic, that is, built into the genome at conception!  Again, then depending on who such knowledge is important to, individuals in the population can (should, must) be tested.

Of course, it's worth asking carefully whether what's really being looked for are individual differences, or group differences.  Why 'we' (those in power) 'need' (that is, want) to know which of 'their' behaviors are built-in, is unclear, but seems frequently to justify acting in discriminatory ways, favoring some and neglecting others.  In other words, of course intelligence is the result of gene action, but the argument is really about variation rather than mechanism.

But before we address these issues, it is worth providing a quick description of the core of the 'scientific' basis of the argument, which typically rests on a measure called 'heritability' (denoted here by H but typically written h-squared).

Heritability: simple-sounding word, but a slippery measure
When the genetics of intelligence, or most other behavioral traits for that matter, is considered, the proof that they are genetic is usually that their heritability is high.  Heritability has been known for decades to be a rough indirect indicator of genetic mechanistic cause, but it's a very elusive measure. The usual measure of H is basically the ratio of the amount of variation in genes (G) divided by the amount of variation in genes + variation in environment, G/(G+E), all within a particular sample at a particular time.  This is estimated typically by comparing the trait measure in relatives, since close relatives share specifiable fractions of their respective genetic variants.

This figure schematically shows the scatter of genetic similarities, each dot being values of the measure in an offspring compared to the average of its mother and father.  The figure shows the difference in such correlations if environmental effects are great and genetic variation accounts for only 10% of the similarity (left panel), or small where the environments contribute only 10% (right).

From Wikimedia images, taken from Nature

H in itself measures no specific genes or gene-variants, nor any specific environmental variants.  To avoid some confounding or confusing contributors to the trait, various additional types of sample are often studied or comparisons made, such as between adoptees vs biological children, or dizygous vs monozygous twins. Heritability studies also often try to remove correlations among relatives that are due to shared family environments that could, in the computation, falsely appear as genetic.  While these strategies are not useless, they are well-known to be imperfect.

Since the measure H is a ratio that depends on the particular conditions in your particular sample, if one of the terms (G or E) were to change, even within that same sample, the H value would also change. In other words, let the same population (the exact same set of genotypes) experience changed environments, and H will change. In that sense H is not an absolute measure of how genetic a trait is, but of how relatively important it is.  Let us repeat that--heritability is not a definitive measure of the genetic contribution to a trait.  It is about its context in a particular sample.

Every study of traits like IQ test scores, used as hopeful stand-ins for 'intelligence', shows that there is substantial heritability, though usually far below 1.0.  That means that environmental effects are important, usually predominant, even if genetic variation is contributing as well.  That's about all that H measures show.  'Environment' in this sense tells us nothing in itself about what the specific individual contributing factors might be, because they don't behave the way genetic factors do, thanks to the rules of genetic transmission from parent to offspring; environmental factors don't have theoretically specifiable patterns of clustering among people or even among relatives. The apparent environmental component estimated in H studies can also include things like chance, testing inadequacy, measurement error and so on.

The undeniable bottom line is that variation in traits like intelligence test performance is certainly affected by genetic variation because the trait itself is mechanistically affected by genes. But that is a crude and almost useless fact because the genetic component is generally polygenic, meaning that it is affected by large numbers of varying genomic elements, each making very small individual contributions. Here, we conveniently ignore whether current fad factors such as microbiomic or epigenetic effects are relevant, because each of them is variable, in each population or sample, and over time--even in each individual over time--and could in principle be inherited and hence appear in families as being 'genetic'.

What this means is that even each individual's inborn genetic component will be very different, that is, each of us will have different combinations of variants at tens or hundreds (or more) of contributing gene regions.  The predictability of achieved results from genomes, much less individual variants, will be correspondingly small, practically useless, as we've clearly seen for so many other complex traits (GWAS results, for example, even of IQ test scores). If we could measure environments the way we can measure genomic variation, they would be similarly complex with many individual factors involved, most with individually weak effects.  As with genotypes, the complexity of these environmental factors would mean each person is unique and predictions are weak, and that changing circumstances and imprecision in the risk estimates would have a large potential effect on each person's achieved results.  We've discussed these limitations (and the overselling) of genetic association studies many times here.

But, if one is determined to pry into everyone's inherent worth, here's how to do it properly:
Here's an idea: Let society decide that we want to know the real genetic truth about behaviors, not just the mechanisms but the effect of variation among individuals.  To do that, we must pass legislation to ensure that all environmental factors that contribute to behavior--all of them!--are exactly the same for everyone, from conception onward.  Once that is done, variation in test performance will be entirely due to genes, since the environmental variance, E, would be zero, so that H would be 1.0.  Now we can see how strongly genes in general, or individual genetic variants, determined results.  However, we assert with confidence that the result of individual genetic prediction would still be hopelessly complex in most cases (excepting, for example, clearly pathogenic genetic variants, which we know to be rare, and even they are usually not simple).

But this is of course a fantasy: making environmental effects uniform for everyone is obviously impossible, for at least two reasons.  First, we can't make the climate in Maine like that in Florida or California.  We can't have identical schools everywhere, or the same number of books in every home, or the same number of words spoken to each infant at each developmental stage.  And so on.  So maybe a more realistic idea would be to make the environmental variation the same everywhere, so that in a sense it was a kind of uniformly distributed 'error' term in measuring genetic effects.  Of course that can't be done either, for the same sorts of reason.

Secondly, genes don't work on their own, but interact with 'environments' in almost every imaginable way, and certainly in the development of the brain.  That means that separating G and E (as in G+E) is clearly an oversimplification of something very poorly understood.  Even fixing the same environment everywhere would not have the same effect on every genotype.

The bottom line, in reality, is that arguments, usually by those in privilege, that behaviors (and hence their societal value) are inherent, are almost inevitably working some other form of self-advantaging agenda.  Racism is right beneath the surface in much of this, but so are xenophobia and class differences.  So are hopes of producing babies with some desired property.  That's clear from the history of the subject.

Since it's impossible to think that society could make environments uniform for everyone so all that's left is genetic variation, the next most salubrious thing a society could do would be to provide the best environmental conditions for all of its members to thrive in, not expecting everyone to achieve the same but at least to have safe, satisfactory lives.  More socioeconomic equity by the elimination of poverty and privilege would be a solution if such equity were the real objective. Of course since the beginning of history this has been the stated goal of those who bemoan the unfairness of society (though less so of others who say we're inherently unequal and we ought to reward the privileged).  We gain little by peering into individual genomic 'souls' and condemning those found genetically wanting to fates that we, in the elite, decide is best for them (inevitably making sure we stay at the top).

This doesn't seem too cynical a view of the subject: If what those who assert the deep importance of genetics of behavior really want is for society to be fair, the first thing is to understand the environmental effects that obviously are the predominant causes of behavioral variation, and rectify the inequities.  Let society ensure that everyone has the same conditions: no upper class advantages in schools, ballet lessons, Kaplan prep courses for SATs to get them into Princeton, no jobs to get through family or parents' contacts, same number of books in every house, no corner drug dealers nor rats in the hallways in poor neighborhoods......  Or, how about broader 'intelligence' testing ideas, to include smarts like the ability to read defenses in basketball while flying through the air, or work a fork-lift efficiently, or fix one of today's complicated cars....

H is a complex factor that is misused as much as it is used, because there are too many reasons to interpret its computational subtleties in ways that conveniently favor one's own social agenda. Not everyone interprets these issues in this way, but behaviors like intelligence are too juicy for those with such intentions to resist.  But, yes, let's be scientific, and commit to a concerted effort to make H approach 1.0, so that we can really understand the genetic contributions--that is, to make test-score differences really 'genetic'!  Then we could make sense of 'genetic' causes.  But, would any serious thinker believe it would be very useful?

The fluidity of fluid intelligence

If IQ is a measure of some aspects of intelligence, and intelligence is the product of a gene or genes, then it should follow that IQ is a stable trait during an individual's lifetime. So I was interested to hear on a recent episode of the BBC radio program, Analysis, that IQ can change even over the course of participation in a brief psychological study.

Princeton professor of psychology and public affairs, Eldar Shafir, co-author of the book, with economist Sendhil Mullainathan, "Scarcity: Why Having Too Little Means So Much", was interviewed  on the program about how having too little time or money influences our lives.  Mullainathan and Shafir believe that experiencing scarcity changes the way we think, and makes a bad situation even worse; poverty creates a "scarcity mind-set" and causes poor people to make bad decisions, which perpetuates their poverty.

To test this, they interviewed people shopping in a mall in New Jersey, determined their financial status, presented them with various financial scenarios and then asked them to play computer games that measured their 'fluid intelligence', a component of IQ that indicates things like the ability to think logically, to reason, or to handle novel situations.

When the scenario is manageable, if for example they are asked what they would do if their car breaks down but it won't cost much to fix, poor and rich people perform equally well on the tests.  But if the scenario is challenging, say fixing the car costs $1500, rich people did as well on the intelligence tests as they did before, but poor people did significantly worse.

Mullainathan and Shafir contribute this to scarcity of what they call 'bandwidth', or the amount of mental capacity that is used to make decisions.  They found that IQ fell by 13 points in their poor study subjects given a challenging scenario.  This, Shafir said, can be equivalent to a drop from borderline gifted to average, or average to borderline deficient.  Shafir contrasted this with a night without sleep, which leads the IQ of the sleep-deprived to be 10 points lower than usual.

Scarcity has other effects as well, according to Mullainathan and Shafir, leading people into a cognitive 'tunnel' so that they can't think broadly about how to solve a problem.  Shafir describes it this way in an interview with the the American Psychological Association:

Every psychologist understands that we have very limited cognitive space and bandwidth. When you focus heavily on one thing, there is just less mind to devote to other things. We call it tunneling — as you devote more and more to dealing with scarcity you have less and less for other things in your life, some of which are very important for dealing with scarcity. There's a lot of literature showing that poor people don't do as well in many areas of their lives. They are often less attentive parents than those who have more money, they're worse at adhering to their medication than the rich, and even poor farmers weed their fields less well than those who are less poor.

Clearly this can become politically volatile very quickly; right-wingers might interpret these results as indicating that poor people doom themselves to poverty, while left-wingers interpret them to show that poverty begets poverty.

But it's the effect on IQ that interests me, and yes, this is another subject that gets volatile very fast. How can this thing, that so many believe is genetic and therefore relatively fixed, change so readily, and in fact predictably?  This is not the first time that fluid intelligence has been shown to be, well, fluid.  A 2007 paper in PNAS showed that it is trainable, and can be significantly improved, e.g., and methods for improving intelligence, something previously thought to be impossible, are now rife.

If true, this doesn't mean that genes have nothing to do with intelligence -- whatever that is -- though it does mean intelligence isn't fixed.  Perhaps intelligence can be thought of as analogous to blood lipid levels, say; we may be genetically predisposed to high or low cholesterol, but we can raise or lower our levels with diet, exercise, or medication.  That is, as every trait, it has a genetic scaffolding, but it is also influenced by experience.  And, as with intelligence, some people have extreme cholesterol levels, generally due to single or few genes.  However, generally, these are genes that don't influence cholesterol levels in people between the extremes.

This is of course one implication of the clear fact that the 'heritability' of intelligence is well below 1.0, meaning that environmental factors are important as well as genetic ones.  The volatility of the measure is, however, an indicator that even the trait itself may not be very stable and that 'environment' may not refer just to random non-genetic factors but ones that systematically affect the measure.  In this case, the environmental factor could suggest that people in poverty are poor because of low-IQ genotypes, but Mullainathan and Shafir believe it's more complicated than that, that poverty creates a mindset that perpetuates poverty.

Similar kinds of issues apply to most complex traits.  Heritability can vary with age as well as many other factors, because the impact of environmental factors can change, and perhaps for genetic reasons as well.  Some genetic factors may be expressed differently at different ages.  A major issue in general in regard to complex traits would be if the genetic component doesn't just fix a certain fraction of the trait value, but is volatile.  Then the time and way of measurement could generate values that are taken as more inherent and permanent, but in fact are more widely variable.  The variation could be such that the genetic component is far less relevant than is often thought.  Of course it could be the other way round.  In each trait if we are determined to identify how much is inborn and how much acquired, it may be that we need to be much more knowledgeable about the determinants, and more careful in how we measure traits -- or how we 'label' individuals.

Smarten up....but do it quickly!

To what extent is  'intelligence' genetic?  That is, to what extent is your intellectual ability a native ability rather than something learned or developed?  This has long been a very heated 'discussion', not because it's about individuals with truly impaired intellectual abilities, which can often be due to known genetic mutations.  Instead it's largely been about groups, that is, 'races', and it's therefore inextricably related to society at large.

One argument that IQ (here, we let that stand for whatever is measured, without making any supportive judgments that, or when and where it is an appropriate measure of something).   Heritability of IQ is not-trivial, generally estimated to be around 80%.  The remaining 20% is 'environment', and measurement error and the like.

xkcd: Idiocracy

Previous studies had shown the tremendous advantage that early exposure to language and complex concepts has on later development, and that means later school success, and that means higher IQ test achievement.  Prior work showed that by age 3, children from privileged professional families had heard millions more words spoken than children from unpriviliged families.  They also had heard many different words spoken and learned their use.  Now, the NY Times reports that this difference can be detected even by or before age 2.  Samples were small but the study reinforces the idea that very early experience is telling throughout later life.

So what?
Those who see important group differences in IQ are going to defend their viewpoint by saying that they know very well about environmental variation and take that into account but that early experiences cannot obscure the entire group difference.  We don't happen to agree, and this is clearly a matter of personal politics all round, but there are a couple of questions that are fair to ask.

First, is it possible that the actual heritability of the measure is much lower than its estimates?  If social class is correlated in families, say by neighborhood, race, or education etc., then this can inflate heritability estimates, showing similar values for similar reasons, in professional as well as lower SES families.  This is why adoption studies are often used to show the true heritability, but even there there has been evidence of SES correlation in adoptions.

Secondly, if SES inequality were removed from the picture, the overall heritability might stay the same but there would be no difference of the average and far less variance (variation among individuals) among what were previously very different SES groups.

Third, education policy strives and presumably would strive even harder, to standardize what children are taught from birth on up.  They'd be taught or exposed to what our society values, be it vocabulary or mathematics or music or sports.  IQ test scores could increase steadily, as they have done for the past several decades, by making the most of everyone's inherited abilities.

There will always be those who are unusual on this or any other kind of value-score system.  There will be those who are seriously impaired or seriously gifted, however the neural mechanism works.  But the issues of group differences would largely if not entirely disappear; there will always be some average difference between any two groups that are compared on almost any measure of attributes, but that doesn't make the difference 'important', which is a social judgment.

The current study doesn't take us all the way back to Freudian ideas that the first glimpse an infant has of the world is hugely transformative, though who knows what further studies might find.  In any case, the important fact is not about the IQ controversy, because there is no reason to doubt that an enriched environment throughout life is an enriching fact of life.

Care....and be smart! Is it in your genes?

A new article in the 'early edition' of PNAS suggests that IQ tests are not so simply interpretable as some might believe, or wish.  Duckworth et al. ('Role of test mutation in intelligence testing') show that not just the raw DNA in a person, or his/her environmental circumstances such as diet and books in the house, but also motivation affect both the score and the usefulness of the test in predicting life success.

The authors studied 2008 individuals and found substantial increases in IQ test scores by highly motivated participants, greater for those with lower baseline scores.  IQ scores predicted many aspects of life outcomes, but basically not after motivation in taking the test was taken into account.

No matter how you may feel about the Nature-Nurture debate in regard to intelligence, this paper is yet another example of the complexities of biological causation.  In itself, it's probably a minor study relative to the larger question of how much of what an organism is, is 'inherited' in its genome, and how much is due to many other factors of its life-experience.  The authors themselves temper their interpretation.

However, the relevance to societal issues is great, since much in your life depends on how well you fit into the system that assigns resources and rewards, and because discrimination, positive and negative, results.  This affects your social 'fitness' and one can debate if it affects your evolutionary fitness.  But the question goes far beyond the political.

If organisms can be predicted from their genomes, then environments don't count much.  That is relevant to GWAS and personalized medicine, of course, but also to evolution itself.  If genomes are predictive we can effectively forestall disease.  That would be good (though it's largely not true).

But what about evolution?  The idea of evolution in the adaptive Darwinian sense is that genomes are predictive in the context of the environment!  That is what adaptation is all about--adaptation to the environment.  It is those genomes that, in their environmental context, proliferate the most.

This at its very core means that genomes cannot in themselves be predictive.  Or, put another way, adaptive Darwinian evolution can only occur to the extent that genomes are not predictive of the organism's traits.  In this sense, genomes evolve as respondents, not determinants.  In a static environment genomes might become predictive, or seem predictive, but that would be because of the environment, not in spite of it.

The politics of IQ testing and its many, sometimes evil, heads is not our point here.  Again, we just take this story as an illustration of the elusiveness of biological causation, and the subtlety of the Nature-Nurture phenomenon.

"Multikulti is dead"

Now
Sometimes we ask ourselves if we're way out in left field when we occasionally caution that the wave of new genetic determinism needs to be watched lest it be a harbinger of a new era of eugenics.  Objections to this say that the new genetics is for biomedical and other improvements, not negative discrimination--but that, of course, privacy is needed to protect against the misuse of data by, for example, insurance companies.

And then an Angela Merkel will declare, to a standing ovation, that multiculturalism has 'utterly failed' in Germany.  Germany, of all places.

At "the beginning of the 1960s our country called the foreign workers to come to Germany and now they live in our country," said Ms. Merkel at the event in Potsdam, near Berlin. "We kidded ourselves a while. We said: 'They won't stay, [after some time] they will be gone,' but this isn't reality. And of course, the approach [to build] a multicultural [society] and to live side by side and to enjoy each other ... has failed, utterly failed."

The crowd gathered in Potsdam greeted the above remark, delivered from the podium with fervor by Ms. Merkel, with a standing ovation. And her comments come just days after a study by the Friedrich Ebert Foundation think tank (which is affiliated with the center-left Social Democratic Party) found that more than 30 percent of people believed Germany was "overrun by foreigners" who had come to Germany chiefly for its social benefits.

The study also found that 13 percent of Germans would welcome a "Führer" – a German word for leader that is explicitly associated with Adolf Hitler – to run the country “with a firm hand.” Some 60 percent of Germans would “restrict the practice of Islam,” and 17 percent think Jews have “too much influence,” according to the study. 

And the far-right is gaining all over Europe from an anti-immigrant backlash -- largely, but not entirely, anti-Muslim.  Many Roma have been deported from France in the last few months.  And of course this anti-immigration fervor is not restricted to Europe.  Here in the US we've got a level of rage we haven't seen for decades, as Frank Rich writes in the Sunday NYTimes.  And we've got the Tea Party movement, which officially is calling for smaller government, lower taxes, and strict interpretation of the Constitution, but the group is apparently most attractive to those with, shall we say, less than inclusive views.  Here we've lifted a paragraph from the Wikipedia description of the Tea Party:

Various polls have also probed Tea Party supporters for their views on a variety of political and controversial issues. A University of Washington poll of 1,695 registered voters in the State of Washington reported that 73% of Tea Party supporters disapprove of Obama's policy of engaging with Muslim countries, 88% approve of the controversial immigration law recently enacted in Arizona, 82% do not believe that gay and lesbian couples should have the legal right to marry, and that about 52% believed that "lesbians and gays have too much political power."

So the background of us vs. them is building.  What about the will to translate that to genetics?  Well, here's an excerpt from in an interview published in New Scientist with Slavoj Žižek, Slovenian philosopher and commentator:

You were in China recently and got a glimpse of what’s happening in biogenetics there.

         In the west, we have debates about whether we should
         intervene to prevent disease or use stem cells, while the
         Chinese just do it on a massive scale. When I was in China,
         some researchers showed me a document from their
         Academy of Sciences which says openly that the goal of
         their biogenetic research is to enable large-scale medical
         procedures which will “rectify” the physical and physiological
         weaknesses of the Chinese people.


Is this true?  We can't confirm it, but it wouldn't be a surprise.  Not because it's China, but because we are in an age of belief in biotech and our ability to harness it to our will.  If it isn't true yet, it will be -- somewhere.

The New York Times is reporting that there is now a new museum exhibit open in Germany that shows that the holocaust was not something Hitler and his henchmen foisted off on a benign, unaware populace.   Instead, the populace put him into power.

Then
There are many parallels between the rhetoric of the early Darwinian age, that started out piously voicing the idea that science could now improve humankind via genetics, and the kinds of rhetoric, such as we're citing here, that we hear so often today.  It started out mainly benign or even positive in the early eugenics era (encouraging the best of us to reproduce, and discouraging voluntary restraint on the rest of us unwashed).  But of course it turned coercive -- first in medicine, by the way -- and then murderously hateful.

Historically, this kind of thing happens most when a society is under stress.  We're seeing a version of that stress in the current recession -- the anger is palpable.  Is democracy robust to the schemes of the demogogues who would like power and would use emotive, anti-immigrant or religious crusading arguments to start a 21st century version of the eugenics era?  Hopefully so.  But there is much general societal parallel, including much of the rhetoric and even invocation of Darwinian concepts (or their pious, medicalized, benign-sounding equivalent), so that one can't just dismiss the possibility.

Personalized genomic medicine can become personalized genomic discrimination.  If concepts like 'racial profiling' take hold, 'personalized' can become 'personalized + race'.  And we have to realize that if we believe that genome sequence can predict risk for essentially all disease traits -- and that's basically the claim, or hope -- then there's no reason to also believe that other traits, including socially sensitive traits, will not be equally predictable.  This is what happened before, except that specific genes were not known (other criteria were used, such as family patterns).

And if you believe that you can predict complex disease effectively and if you believe in 'Darwinian' medicine, then you'll also be prone to argue that normal traits -- whatever suits your personal interests to advocate -- also reflect natural selection.  And that by definition means you place value differences on different versions of the trait -- like IQ. And if you believe these were selected differently to an important extent between  human populations (i.e., 'races'), then there's a short line from there to drawing value judgments about races.  And then you can worry about the inferior individuals out-reproducing the superior and being a danger to society down the road.  This is exactly the trail or reasoning that we've been through before.

Now?
We aren't saying that this is all happening now, as we write.  We're just saying that, for those with antennae for this sort of them vs us view of the world, the antennae are picking up signal. The lesson from the history of eugenics and what it spawned is that, like the fog in Carl Sandberg's poem, this stuff creeps in on little cat feet.

The way to a man's heart is .... through simpler nutrition labeling?

A headline today from the BBC: "Lower IQ 'a heart disease risk'". This is a report of a paper in the European Heart Journal in which researchers looked at the life experience of more than 4000 US Vietnam vets and concluded that IQ alone explains 20% of the risk of heart disease. They controlled for known risk factors such as smoking, diet, exercise and socioeconomic status (heart disease risk is already well-known to be higher among people with lower income and education levels, and smoking, diet and exercise are associated with SES as well), and still found an IQ effect.

Clearly, however, if this association is real, low IQ is not the direct 'cause' of heart disease--unless someone truly believes that 'brain' genes affect heart function such as clogging of arteries! Instead, IQ is a confounder, a measured variable that is not directly causal but is correlated in the sample with some unmeasured truly causal exposure factor, be it genetic or otherwise.

But confounder for what? The lead researcher suggests that the problem may be that people with low IQ may have trouble heeding health advice. It needs to be simpler and easier to understand.

"For instance, we often read about how some types of alcohol are good for you while others, or even the same ones, are not. The messages can be difficult to interpret, even by knowledgeable people."

This is an interesting quote because it (presumably unwittingly) points out that health advice is often contradictory, not to mention highly cultural. And thus impossible to interpret meaningfully, no matter your IQ. Some alcohol is good for you--except when it's not. Hard to think how you could make that into advice that's easier to follow. The other interesting bit about this quote is that the alcohol he's talking about is red wine, more generally the drink of choice among the middle and upper classes.

That aside, what could IQ be a marker of? Many people suspect IQ scores to be nothing but cultural markers--indeed, it's well-known that they vary by race, and have been changing rapidly over recent time, for largely cultural reasons. So IQ would be a marker of race, but the BBC story doesn't mention race, because the paper itself doesn't, either. Unbelievable!

One can hardly imagine an aware US epidemiologist who would not think right off the bat that race may well be the real risk factor here, for which IQ is a correlated marker. Heart disease risk is higher among African Americans, and presumably, if this particular study group follows known trends in IQ scores, African Americans would be more heavily represented in the lower IQ scoring/higher heart disease risk group. Thus, IQ is merely a marker for race here, and the risk associated with race.

But, let's run with the idea that intelligence might actually be a risk factor for heart disease. Numerous studies have been done to try to identify genes 'for' IQ, but with little replicable success. But let's suppose there are genes 'for' intelligence--indeed, if the IQ/heart disease association is real, mapping studies looking for genes associated with heart disease should have at least identified IQ genes. (But determining whether genes are IQ genes or not would be difficult because 70-80% of genes, no matter where else they are expressed or what their known function(s), are expressed in the brain--are they all 'brain genes' or genes for intelligence?). Indeed, genes 'for' poor circulatory function may affect ability to study and learn, so the reverse should also occur: IQ mapping should pick up cardiovascular genes!

Further, if this association is real, it raises the question of causality. But what 'causes' AIDS? Is it the HIV virus? But, HIV/AIDS rates are highest among the poor, so was Thabo Mbeki, the former president of South Africa, at least partly correct when he insisted that HIV/AIDS is caused by poverty? So if low IQ is a marker of race, and SES, do poverty and racial discrimination cause heart disease?

This study was carried out by British researchers. One wonders if their less nuanced understanding of American race and class issues erroneously led them to conclude that an effective way to lower heart disease is to make nutrition labeling easier to understand. Or could they be from such a middle-class environment as to be insensitive to these kinds of issues?

Or could it be that the general operating notions of causation, based as they are on stereotypical study designs that look for statistical associations, are a barrier to understanding?

As usual, genetic causation today and genetic causation as the result of evolution are similar. If natural selection favors some trait, then any genetic variation that gets the favored state will be favored. If variation in IQ genes led our ancestors to pick low-fat fruit (say), then those genotypes would be favored by selection just as fat-metabolizing genes would. If they could be detected by the kinds of searches for evidence of selection that many are doing these days, much experimental effort could be wasted trying to show how those genes were involved in lipid metabolism.

This is a subtle world today, and it's been that way throughout our ancestry.

Science is based on cause and effect, which is not identical to correlation and effect. The meaning of 'cause' has been central to philosophical thinking since Aristotle. Perhaps we should be less driven by methodology and pay more careful attention to that in science today.