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Note that the article is not saying that intelligence is not heritable. In fact it makes it quite clear that despite the controversy, the opposite is true: >

Note that the article is not saying that intelligence is not heritable. In fact it makes it quite clear that despite the controversy, the opposite is true: > 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).

tokenadult 13y ago
It may be useful for the discussion here to define what "heritable" means. I like what Eric Turkheimer, a psychologist who investigates the heritability of human intelligence, says about that. "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%20Online%20CV/Turkheimer%20(2008).pdf http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O...
- jcampbell1 13y ago
  > Heritability isn't an index of how genetic a trait is. 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?
  - Symmetry 13y ago
    I think the author is saying that the heritability of a trait depends on the range of environments being considered, but saying it in a needlessly grandstanding and obfuscatory manner? 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.
bayesianhorse 13y ago
For all practical purposes, "intelligence is largely not heritable" is actually closer to the truth than the opposite. 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...
- rayiner 13y ago
  IQ is highly heritable: http://en.wikipedia.org/wiki/Heritability_of_IQ#Estimates_of_the_heritability_of_IQ http://en.wikipedia.org/wiki/Heritability_of_IQ#Estimates_of... (estimates of adulthood heritability are 0.7-0.8, similar to height). 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.
  - bayesianhorse 13y ago
    I qualified my statement with "for all practical purposes". I have often claimed that there is no practical relevance and no reasonable way to use this "fact" in practical real world decisions. Nobody was able to tell me one that holds up to even superficial checking. "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...
anaphor 13y ago
IQ becomes more heritable the more homogeneous an education and development a group has. So it is probably less heritable in a very poor country where there is a large disparity in the kind of nutrition and education someone has access to (lots of very rich and very poor people).
ekm2 13y ago
>Note that the article is not saying that intelligence is not heritable. And heritable does not mean it is unchangeable.

tokenadult 13y ago

It may be useful for the discussion here to define what "heritable" means. I like what Eric Turkheimer, a psychologist who investigates the heritability of human intelligence, says about that. "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%20Online%20CV/Turkheimer%20(2008).pdf http://people.virginia.edu/~ent3c/papers2/Articles%20for%20O...

jcampbell1 13y ago
> Heritability isn't an index of how genetic a trait is. 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?
- Symmetry 13y ago
  I think the author is saying that the heritability of a trait depends on the range of environments being considered, but saying it in a needlessly grandstanding and obfuscatory manner? 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.

bayesianhorse 13y ago

For all practical purposes, "intelligence is largely not heritable" is actually closer to the truth than the opposite. 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...

rayiner 13y ago
IQ is highly heritable: http://en.wikipedia.org/wiki/Heritability_of_IQ#Estimates_of_the_heritability_of_IQ http://en.wikipedia.org/wiki/Heritability_of_IQ#Estimates_of... (estimates of adulthood heritability are 0.7-0.8, similar to height). 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.
- bayesianhorse 13y ago
  I qualified my statement with "for all practical purposes". I have often claimed that there is no practical relevance and no reasonable way to use this "fact" in practical real world decisions. Nobody was able to tell me one that holds up to even superficial checking. "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...

anaphor 13y ago

IQ becomes more heritable the more homogeneous an education and development a group has. So it is probably less heritable in a very poor country where there is a large disparity in the kind of nutrition and education someone has access to (lots of very rich and very poor people).

ekm2 13y ago

>Note that the article is not saying that intelligence is not heritable. And heritable does not mean it is unchangeable.