Recently I posted about a popular formula for estimating heritability (H^2):
H^2 = 2[(correlation between MZ twins raised together) – (correlation between DZ twins raised together)]
This formula assumes that since MZ twins share twice as many unique genes as DZ twins, then if a trait is heritable, MZ twins should correlate much more strongly than DZ twins do.
Implicit in this formula is the assumption that since MZ twins reared together and DZ twins reared together, both shared the same home, and were both born to the same mothers, then the only reason why MZ twins would be more similar in a trait is because they are more genetically similar. Thus the greater the similarity of MZ twins compared to DZ twins, the more heritable the trait is thought to be.
However a major flaw with this model is that MZ twins are not only more similar than DZ twins genetically, but at least before birth, they are more similar environmentally, because MZ twins typically grow in the same placenta while DZ twins almost never do.
One way to correct for this environmental confound is to compare the correlation between DZ twins with the correlation between MZ twins who grew in different placentas (dichorionic MZ twins).
I recently blogged about an IQ study that did exactly that and what they found was that on tests like vocabulary, even when using dichorionic MZ twins, you still get the sky high heritability estimates that traditional twin studies found. However on a culture reduced test of spatial reasoning (Block Design) heritability suddenly dropped to less than 10%.
However that study had a very small sample size, and commenter “Lion of the Judah-sphere” was immediately skeptical.
Well I recently found a similar study but with an absolutely enormous sample size, and the results are very different. In this study, when you take the difference between the correlations between dichorionic MZ twins and DZ twins (see table 2 at the end of chapter 3 of this document), and apply the formula cited at the start of this post, you get a heritability of 0.48 for vocabulary and an astonishing 0.8 for block design. For overall verbal IQ, you get a heritability of 0.72, and for overall non-verbal IQ, you get a heritability of 0.6, and for full-scale IQ, you get a heritability of 0.76.
And this study was conducted on children, so a study done on adults would be expected to yield even higher numbers.
Of course the formula I cited at the start of this post assumes the Phenotype = Genotype + Environment model so disputed by anti-hereditists, however the most formidable attack on twin studies is that they don’t control for prenatal factors. This criticism has now been rebutted, and it’s a great day to be a hereditist.
Beautiful!
Don’t wanna crush your party but…
Approved by Jensen.
crash your party, pardon my French.
norms of reaction is simply beyond the comprehension of hereditists.
they give it lip service, just like they give rich men’s cocks lip service, but they still don’t understand it.
they live in flatland, but the real world is multidimensional.
I agree with the norms of reaction critique; it’s just that the studies needed to debunk it are so hard to do that I’m just going with the P = G + E as a tentative assumption
The norms of reaction critique is undebunkable/unfalsifiable, that’s why anti-hereditists like it so much.
To falsify the norms of reaction critique you would need to test the IQs of 100 regular Americans & 100 of their clones born and raised in the Congo rainforest. Not a realistic study.
And you would get a high correlation but an enormous difference, of at least 2 SD.
If the P = G + E model is correct, you’d get a high correlation but a big difference
If the norms of reaction model is correct, you’d get a low correlation because when environment differs that severely, the non-flatness of the GxE tangent plane would be exposed.
Steve Hsu said that norms of reactiono is just obfuscatory, even the most conservative estimates of narrow-sense heritability would still give you a lot to work with.
The above example could at least describe the consequences of the Flynn effect. No genetic change, no change either in the genetic influences on IQ but a radical change in terms of phenotype.
Knowing better what caused the Flynn effect would probably lead to a better understanding of how environment influences IQ test performance and differences between groups in that matter.
Pumpkin suggests that testing the norms of reaction rule, which is as debunkable as Newton’s law of universal gravitation would require something as crazy as putting the clones of average Americans in the Congo rainforest (It actually wouldn’t change any thing if that’s done in adulthood). What you can do however is comparing MZ twins, one growing up in the third world, the other adopted in a first world country where race consciousness is low, like France. I’m pretty sure my hypothetical Haitian identical twin brother wouldn’t have my IQ, height, weight and life outcomes, even though many things come to blur the line. The fact that I was adopted in a top 10% family, and the hypothesis that I was already genetically well endowed from the start in spite of being born to a slum dweller mother.
Another aspect often forgotten about how people do on those tests is motivation. Many studies that I will let you find out on the internet have shown that adding a reward to the test (like candies or money) greatly altered the average scores. The gains were not uniform however, whereas the high scoring did not see their scores rise with the incentive, the lowest scoring gained about 1 sd.
Adding a common incentive is important, it shows how much brainpower test-takers are able to mobilize in order to get the same reward. Without this parameter, you have those who simply don’t give a fuck, slack off wishing to get back to their business as quick as possible. Others are disturbed by the idea that their intelligence is being tested and now have the opportunity to take the test as a challenge whereas those high already high scoring and experiencing little gains seem to need no help to consider the IQ test as a meaningful and funny challenge.
If you’re skeptical about the effects of motivation on IQ tests, just imagine something different with a bunch of women.
Scenario 1: tell these women to run because we wan’t to see how fast they are
Scenario 2: tell these women that the fastest of them will win a pair of Louboutins
Now guess which score will be the most accurate.
Question: What is norms of reaction argument trying to say, exactly?
If you did a twin study, and kept one half in America, and the other half in the Congo, of course, there would be height differences. The ones in the Congo would be much shorter.
But even hardcore hereditists know that. And they would point out that the rank-ordering of the twins would be the same regardless of where you raised them. If Adam 1 is taller than Bob 1 is taller than Carl 1 in America, then in the Congo Adam2>Bob2>Carl2 in height– although the Congo half might be about 5 inches shorter.
No one denies that large environmental changes impact traits, the question is whether environmental variations within 1st world countries have any significant impact on phenotype– and the answer is NO!
The “norms of reaction” argument would only be worth discussing if 1) small environmental changes had dramatic impacts on highly heritable characteristics, or if 2) changing the environment had impacts on rank-ordering of characteristics.
Question: What is norms of reaction argument trying to say, exactly?
That the rank order would change. John might be taller and smarter than Joe when born and raised in America, but had John and Joe both been born and raised in the Congo, Joe might have been taller and smarter than John.
Thus they argue that there’s no such thing as genes for IQ or genes for height, there are simply genes that enhance IQ or height in environment X, but might reduce both traits in environment Y.
Thus studies of identical twins reared apart are dismissed as meaningless by these people, because even the apart twins share the same country (or similar countries), and so the correlation between them only shows they have genes that cause high IQ in society X, not that the genes have a truly independent causal effect on IQ.
Another aspect often forgotten about how people do on those tests is motivation. Many studies that I will let you find out on the internet have shown that adding a reward to the test (like candies or money) greatly altered the average scores.
I’ve seen a IQ researcher by the name of Angela Duckworth publish on that years ago.
There’s no doubt IQ is partially measuring conscientiousness/motivation, but it seems that even that trait is highly genetically determined. It should be no shock that those more innately motivated by intellectual tasks do well on IQ tests. IQ test scores maintain their high validity in determining life and school outcomes, regardless of whether or not they’re measuring motivation.
“There’s no doubt IQ is partially measuring conscientiousness/motivation, but it seems that even that trait is highly genetically determined.”
Proof it’s not, we are able to increase motivation by giving everyone an equal goal, not by changing their genetics.
“IQ test scores maintain their high validity in determining life and school outcomes, regardless of whether or not they’re measuring motivation.”
School outcomes: sure
Life outcomes: depending on one’s life expectations. But what matters here is that differences when it comes to deploy one’s intellect in order to reach a particular goal are low. If the failing ones somehow found reasons to become successful, they have the ability to do so but those we call failures do not perceive themselves as such, they are successful in the goals they pursue. The only ones who can’t achieve any objective they set are the true retards or mentally deficient.
“Question: What is norms of reaction argument trying to say, exactly?
That the rank order would change. John might be taller and smarter than Joe when born and raised in America, but had John and Joe both been born and raised in the Congo, Joe might have been taller and smarter than John.”
No, they try to say what Lion mentioned before.
“The “norms of reaction” argument would only be worth discussing if 1) small environmental changes had dramatic impacts on highly heritable characteristics, or if 2) changing the environment had impacts on rank-ordering of characteristics.”
Nutrition has a dramatic impact on health, height and weight, regardless of genetic predisposition.
Medication has a dramatic impact on managing and even stopping symptoms of some genetic disorders or traits
Asians came to have IQs above whites because their Flynn effect brought them 7 IQ points in more per decade compared to 3 in the West…
steve shoe is a moron carl. and he’s yet another example of one who claims to understand norms of reaction and then dismiss it, yet it’s VERY clear from reading him that he does NOT understand it.
he may even be dumber than you carl.
he’s proof of spearman’s law.
he can do some math. but other than that he’s just the typical pushy striving obedient uncreative fucktard which is systematically preferred in les etats unis merdeux.
his latest post says that “knowing how to handle a gun is an essential life skill”.
wtf?! it’s NOT a “life skill”, let alone an essential life skill. ANYONE with a gun who doesn’t use it to kill animals he EATS is a PROLE FUCKTARDED FUCKTARD.
his parents are immigrants. he can’t help it.
btw, i KNOW!
steve shoe has made several blatant, patent, etc. mathematical errors on his blog.
i corrected them, and he “banned” me.
he left the UO because he was such a HORRIBLE physicist.
If I remember correctly, you didn’t point out anything at all. Indeed, all your comments on Infoproc were obfuscatory.
We’re at the point now where every prediction of the”hereditists” is coming true. We have GWAS and GCTA hits, multiple twin studies, and more. The g factor can be found in cognition of several animals. The g factor has several neurological correlates.
We have new discoveries left and right, and all the deniers like you can do is make obfuscatory comments which mean NOTHING. All this was true ever since Steven Pinker published The Blank Slate. Ever since Jensen published the g factor, we’re just now confirming their theories.
Like Charles Murray said, in 20 years, “hereditists” who were battered and bullied by politically correct egalitarians are going to be seeing every theory of theirs vindicated, a bit of schadenfreude notwithstanding, of course 😉
Cognitive dissonance…..
Twins studies seems very good to refute against environment-behaviourism premises. But twin studies is not exactly about heritability, intergenerational transmission of traits, father from son. Is about genetic similarities between twins, specially monozygotic.
Analyse monozygotic, those who are very very similar one each other, is like analyse ourselves, as if we had a twin or even a clone. In different environments, we would change little in our respective essences.
it is clear that the circumstances would be different and that depending on our behavioral plasticity, our tolerabilities, our predispositions, which could react differently, but I doubt this would reverberate in essential transformations.
There are people who are more resistant to external influences, have strong personalities, while others are more vulnerable. For example, in a risky environment to become criminal, always have one that will never be influenced by the glamor of thug life. On the other hand, we also have types that will be partially influenced. To the opposite end of the spectrum, where life thug shine something essential of some types (men, mostly) personality, we will have what the hbds habituates to call gene-culture coevolution.
Environmentalists are partially correct about the fact that the type of environment can, and usually have an impact on our long-term to short reactions. But even our response plasticity, it is clear that is not based on a paranormal phenomenon, but a panacea for susceptibilities of behavioral responses (read genes) that depend on the interaction with the environment and it will also be very variable, in fact, our own environments vary greatly, because we need to get around in different regions, with different customs, different technical needs, we need to modulate our behavior at all times.
Therefore, to deny that human biology has a crucial role in the behavior is the same as believing in paranormal events.
Most people, from what I gather, are not like super-talented chameleons, only the most psychopathic types. Most people adapt partially / superficially, the conventions of different environments, especially when there is empathy / reciprocity or tolerability. The average human being to appropriate the cultural memes to get any benefit from making friends to make money. Everything they do, what we do need to have advantages, even pathological altruism, has a huge psychological gratification.
inter alia, hereditism is an attempt to NATURALIZE what is NOT natural.
humans are unique. UNIQUE! in the range of physical environments they inhabit. and ON TOP of that, the range of cultural environments they inhabit. the physical environment which most live in today is MAN-MADE.
does any other animal have a range of cultures? can any other animal change his environment?
an algerian jew:
http://biblioklept.org/2011/09/22/one-of-the-gestures-of-deconstruction-is-to-not-naturalize-what-isnt-natural-derrida-kinda-sorta-almost-defines-deconstruction/
btw, hereditists, proles par excellence, may dismiss the above vid’s transcript as gibberish.
it isn’t.
though almost ALL of late 20th c french “philosophy” IS gibberish, derrida, though often ridiculous, is NOT.
and in fact he was excepted from Fashionable Nonsense, a great book, btw.