Most Reported Genetic Associations with Intelligence are Probably False
dash.harvard.edu
dash.harvard.edu
> Although the exact figures have been the topic of much debate, the claim that IQ is at least moderately heritable is widely accepted. IQ may in fact be similar in heritability to the physical trait of height
What the article is saying is that intelligence cannot be tied to particular genes:
> We sought [and failed] to replicate published associations between 12 specific genetic variants and g using three independent, longitudinal datasets
It just goes to show that there isn't necessarily one particular factor you can pick out to predict intelligence; it is a combination of many things.
(I shall attempt to avert the impending discussion about the word "intelligence" by clarifying that the sense I am using that word is in the same specific manner that the article is: as an objective measure that is statistically correlated with other measures).
"But back to the question: What does heritability mean? Almost everyone who has ever thought about heritability has reached a commonsense intuition about it: One way or another, heritability has to be some kind of index of how genetic a trait is. That intuition explains why so many thousands of heritability coefficients have been calculated over the years. Once the twin registries have been assembled, it's easy and fun, like having a genoscope you can point at one trait after another to take a reading of how genetic things are. Height? Very genetic. Intelligence? Pretty genetic. Schizophrenia? That looks pretty genetic too. Personality? Yep, that too. . . .
"Unfortunately, that fundamental intuition is wrong. Heritability isn't an index of how genetic a trait is. A great deal of time has been wasted in the effort of measuring the heritability of traits in the false expectation that somehow the genetic nature of psychological phenomena would be revealed. There are many reasons for making this strong statement, but the most important of them harkens back to the description of heritability as an effect size. An effect size of the R2 family is a standardized estimate of the proportion of the variance in one variable that is reduced when another variable is held constant statistically."[1]
[1] Turkheimer, E. (2008, Spring). A better way to use twins for developmental research. LIFE Newsletter, 2, 1-5
http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O...
I am totally confused. My understanding is that heritability is a measure of how much genetics accounts for the observed variability in a given environment. I understand both that we don't understand the genetic recipe for height, but also that identical twins grow to be the same height. What is the author saying that I am missing?
Having now read the paper, yes, that was what he was saying, and the non-quoted sections of the paper are much clearer. Example
For the modeling underlying twin studies to make sense, one has to assume that the environments experienced by identical twins raised in the same family are no more similar than those experienced by frater- nal twins, that genes and environments are independent and additive (again, in the usual ANOVA sense) in the determination of the trait, and that parents mate randomly with respect to the trait.
That's totally true. If you compared an organism with a randomly generated genome to a human and exposed both to what would be a normal range of environments for a human, you would find that all traits are entirely genetic. And if you selected people from the normal range of human genetics but only gave half of them access to important things like a uterus then you would find that all traits are almost entirely environmentally determined. So you can't say that "Trait Foo is 50% heritable" unless you also specify the populations and range of environments you're talking about.
EDIT: Or you could say that heritability is ordinal but not cardinal, given some reasonable assumptions.
As long as you can't tie intelligence to particular genes, as long as you can't tell what amount of intelligence in an individual is inherited, and how much isn't, there is no use for this in education, politics or social welfare.
What I see the argument being used for, mostly, is to justify racism and entitlement issues in wealthy people...
We can reject the existence of an observed natural phenomenon because we can't explain it. We still haven't unified gravity with the standard model, but that doesn't mean we reject that gravity exists (for practical purposes or otherwise).
The fact that a natural phenomenon might be socially inconvenient is even less of a good reason to reject its validity.
Finally, I don't even see why it should even be so socially inconvenient. Say the experiments are right, and intelligence is mostly heritable rather than a result of education, upbringing, etc. Why should that justify entitlement on the part of the wealthy? Indeed, it should cut across that grain. If its mostly heritable, being intelligent shouldn't be seen as intrinsically virtuous any more than is being tall. Moreover, the heritability of intelligence may very well imply a need for a change in our priorities when it comes to social welfare. E.g. maybe we need to de-emphasize education, and divert resources to building up social and family networks.
"Socially inconvenient" doesn't even come into it, because twin studies don't tell us anything about differences between two ethnicities. For that matter, genetic diversity within populations might have a larger effect...
The "intelligence is genetic" "fact" is often used to justify refusal to tackle socio-economic problems (like "under-achievement" in blacks or hispanics in the US, or the turkish minority in my home country) with socio-economic solutions. Because hey, it's all genetics, so we can't change it. Even if measures for improvement have been proven...
Changing it wouldn't make a difference, everyone using that logic isn't basing their end goal on it, simply using it to justify their feelings.
Hell it took a while for me to understand the benefit of such improvements, and it had nothing to do with genetics. My problem was few people talk about the socio-economic impacts on capabilities, and the fact that counteracting programs can theoretically stop the death spiral in those groups.
However there are a lot of people who can't get over "not like me" and think the whole thing is a waste because it takes away from "hard working young men".
The fact that intelligence is heritable says nothing about social-economic policy for changing the environment. It is as absurd as saying that because "height is genetic" there is no reason to worry about malnutrition.
The fact that a 'wrongness gene' hasn't been, and may not ever be, identified does not undermine my assessment, but rather indicates current models of the interaction of genes and wrongness might be naive, and the interactions are probably deeper and more complex.
Not saying it's moral, but definitely and obviously practical.
Pedigrees and genetic testing in animal breeding are way more useful. But there you have completely different structures and goals. And some of them, particularly diseases with high heritability like canine hip displasia, can't be solved by current genetics yet.
To take an extreme example where genetics is the clear cause, cats are underrepresented in college. Because we know that cats are genetically less intelligent than humans, we can conclude that affirmative action/college for cats education programs/etc are a waste of money.
Another use would be knowing that if only 50% of the population has the intrinsic intelligence for college, college prep programs should not serve more than 50% of the population (modulo technical details).
And heritable does not mean it is unchangeable.
But the research does have a questionable assumption. On p 5 it says, "Such a result would not likely be due to differences in the methods used to generate g in the various datasets under comparison, since g is consistently measured by a wide variety of tests."
This is true. However it is also true that, as http://vserver1.cscs.lsa.umich.edu/~crshalizi/weblog/523.htm... points out, that all evidence we have is consistent with g being a correlation between different ways of weighting a large number of independent factors. If so, then it is easy to have two test measuring g that are fairly well correlated with each other, one of which picks up a particular factor and the other does not. If a gene affects that factor, then the test you use to measure to find these correlations will matter.
The scientifically interesting thing is that it's not at all like that XKCD cartoon. Multiple hypothesis testing is built into the design of the studies, and has been from the very start. When it comes to proper interpretation of stats in science, geneticists are at the top of the hierarchy.
Your second point is far closer to what I think is going on, but I still think that single-gene studies are the wrong way to go, as you might guess from my username. They're testing for the wrong thing, single locus or single gene causes, of a very complex phenotype with the involvement of many many different loci and genes. So if there are 500-600 genes that are important, maybe one passes the test in your particular subsample, but in a different subsample the rest of the 500-600 genes mediate the effect. I.e. there's not enough complexity in the model to account for the signal. What's worked very well for simple diseases and traits may not work well for complex traits with the influence of many many different genes.
It is built into the design of the studies. But studies that do not find results do not get published. Thus there is a lot of room for exceptional results to sneak through despite the attempts to get the stats right.
It's the same with academic clinical trials, even negative results get published, because for those academics they still need something to show, and a publication of a negative result is better than nothing.
Non-publication bias is more common in less expensive, more exploratory settings, where there are lots of little experiments going on all the time. This is quite different from GWAS.
Something about how P < 0.05 still doesn't mean there is a link between green Jelly Beans and acne?
This is not to dispute his calculations or model - they seem solid. I'm just pointing out that his definition is probably not what most people think when they hear the term.
Skin color makes this much easier to understand. Imagine a couple, where the man and the woman each have one Scandinavian parent and one Bantu parent. Their children could have almost any skin shade.
If they have identical twins, those twins will have the same shade of skin. Skin color is genetically determined but the heritability varies.
Imagine two people who have the same skin color as our first two, but they come from an island population founded by Norwegians and Nigerians exclusively. They are 20th generation, or 50th. Now, it is likely the skin color of their children will be the same as their own.
Intelligence inherits upon many factors. Even identifying those factors proves to be elusive and hard. The good evidence that intelligence is genetic is twin studies: the good evidence that it is variable in heritability is every family you've ever known.
There's nothing here to undermine the view that genetics causes much of variation in intelligence, it's just that the variation wasn't as clustered on a few genes as people hoped because it would make the research so much easier.
Only last week, we had an article on here about how vocabulary in very young children was a function of how much parents talked to their children - with marked differences between economic groups[1]. There are many many systematic errors in this kind of data, and I have no good (ethical) suggestions in how to eliminate them.
The classic way to control for cultural and in-family influences in studies of human behavior genetics is to look for the rare cases of monozygotic ("identical") twins brought up in separate households after adoption. Those studies of monozygotic twins reared apart (MZA twins) set a MAXIMUM figure for the heritability of any trait of interest--because the genes are as similar as they can be between two different human individuals, but the environments, even in separate households, may not be as maximally different as they could be in influence on the trait in question. There is a whole book about the most famous study of identical twins reared apart, which took place at my alma mater while I was an undergraduate and postgraduate student there (in other subjects).
http://www.hup.harvard.edu/catalog.php?isbn=9780674055469
As some people will remember from the press reports at the time, the most culturally variant upbringing two of the separated twins, Oskar and Jack, studied by the Minnesota researchers received was one twin being raised as a Jew, and the other twin being brought up in Nazi Germany and becoming a member of the Hitler Youth.
http://online.wsj.com/article/SB1000142405270230355210457743...
Thank you for the links though, I'll have a read!
This doesn't seem like a surprising result to me. What is being claimed is not "intelligence is not genetic" but it is that "heritability of intelligence is complex". For something that appears as complicated as human intelligence, wouldn't this be expected?
However I'm curious that they chose to use the very-powerfully-determined-by-genes features of Alzheimers and BodyMassIndex as their control. Surely there are other genetic traits that are not 'disorders' which could have been referenced? Breakdowns in physical function would naturally have larger measurable effects than, say, alcohol metabolism rates or whatever.
Studies of the issue of "missing heritability" have often investigated height (bodily stature), which has a very high calculated heritability (resemblance among close relatives) but which must be influenced by hundreds of genes, many of very small effect. Even very extensive genome-wide association studies (GWAS) in large samples find NO gene with large effect on height, and fail to detect most of the presumed associations with height in gene associations investigated in such studies.
The review article Johnson, W. (2010). Understanding the Genetics of Intelligence: Can Height Help? Can Corn Oil?. Current Directions in Psychological Science, 19(3), 177-182
http://apsychoserver.psych.arizona.edu/JJBAReprints/PSYC621/...
looks at some famous genetic experiments to show how little is explained by gene frequencies even in thoroughly studied populations defined by artificial selection.
Should we accept this variance in IQ as genetic and unavoidable? Or should we just buckle down, eradicate Malaria and stop worrying about these factors?
Knowing a lot about genomic animal breeding made me wonder how people can be so sure about genetic basis of intelligence, while we understand neither intelligence nor the genetic basis behind it. For that matter, even plain body height in humans is barely understood...
But not having a concrete definition doesn't make certain inferences impossible.
[1]: Richard Dawkins
"Intellectual and personality measures were available from unwed mothers who gave their children up for adoption at birth. The same or similar measures have been obtained from 300 sets of adoptive parents and all of their adopted and natural children in the Texas Adoption Project. The sample characteristics are discussed in detail, and the basic findings for IQ are presented. Initial analyses of the data on IQ suggest moderate heritabilities." - http://www.ncbi.nlm.nih.gov/pubmed/496798
"Adolescents' IQ test scores were similar to those of their parents and siblings only if they were biologically related. Our interpretation of these results is that younger children are more influenced by differences among their family environments than older adolescents, who are freer to seek their own niches." - http://www.ncbi.nlm.nih.gov/pubmed/6872626
Notice how carefully worded the "interpretation" of that last one was. Rather than suggest that genetics has to do with older adolescence not having IQ scores that match their adoptive parents their "interpretation" is that the adolescences simply chose not to perform as well as their adoptive parents...Anything to avoid controversy.
White guilt is getting in the way of a lot of racial/genetic/intelligence/violence studies. People don't want to go back to a time when one group of humans were seen as superior and another inferior. The funny part is, Intelligence wise, whites are NOT superior. Jews are.. Their intelligence levels are higher, achievement levels higher, hackers should know this. Many of Silicon Valleys most prominent companies were started by jews. Facebook, Craigslist, Google. Also a report by Joel Stein from the New York Times showed that every major Hollywood studio was founded by jews. In the fashion world: Ralph Lauren, Levi (Jeans), Guess, Mark Ecco, Men's Warehouse, and most of the brands you see in stores today were also started by jews.
"In 1921 Budapest, 88% of the members of the stock exchange and 91% of the currency brokers were Jews, many of them ennobled. In interwar Hungary, more than half and perhaps as much as 90 percent of Hungarian industry was owned or operated by a few closely related Jewish banking families. Jews represented one-fourth of all university students and 43% percent at Budapest Technological University. In 1920, 60 percent of Hungarian doctors, 51 percent of lawyers, 39 percent of all privately employed engineers and chemists, 34 percent of editors and journalists, and 29 percent of musicians identified themselves as Jews by religion. Resentment of this Jewish trend of success was widespread." - Yuri Slezkine. The Jewish Century. Princeton, 2004. ISBN 0-691-11995-3
Since 1921 theres been a lot of catching up by Whites, Blacks, Asians, etc... but Jews are still disproportionately successful and score high.
Nature is racist. Us finding out about it is not.
i guess what I'm trying to say is that it'd be fun seeing you try to stand tall and pontificate about the importance of institutionalizing all sorts of unfounded, intuitionist beliefs about race- nevermind the fact that race is hard to determine in a large number of cases- to the detriment of individuals if society didn't put an arbitrary limitation on their exploitation of strength for personal gain
no i guess what i'm trying to say is that usually racists are dweeby ugly little people that stand proud on the shoulders of the achievements of those who they perceive to be 'kin' (nevermind jewish/irish/italian/slav/etc. divisions from yesteryear), and that i wouldn't mind seeing you publicly made fun of and/or beat up because of it.