Honest question that keeps bothering me.
In the absence of reasonably strong natural selection pressure to select for IQ, how could IQ not be falling over time?
replies(5):
In the absence of reasonably strong natural selection pressure to select for IQ, how could IQ not be falling over time?
IQ at best measures something that correlates with SAT. And with better education, less exposure to damaging pollutants, etc. it should always be on the rise (as demonstrated by the Flynn effect; an effect which this poor paper desperately tries to refute).
IQ research has always been about proving the superiority of one race over others, this superiority doesn’t exist, but that doesn’t stop these pseudo-scientist from trying. They bend the definition of “intelligence” and device test batteries (and in this case, interpret test battery) in skewed and bias ways to manipulate results like these. Regrettably media outlets like the Popular Mechanics and lifestyle journalists like Tim Newcomb take these researchers at their words and publish their results, despite their results pretty much being lies.
It is incredibly arguable if during an obesity crisis if population wide health is actually improving and if population wide health isn’t improving that could certainly contribute to lower IQ. We’re also seeing population wide declines of health in other ways like sperm count. Food is becoming less nutritious as soil depletes. Our fish stocks being about to collapse is going to be another hit against brain health as omega 3s will become rarer in the diet.
The heritability of IQ is only well established within true believers of a pseudo-science tightly linked with the eugenics movement. Most psychologists today believe that the supposed heritability was observed because of bias within the research. And given the people who were doing these research in the 1970s and the 1980s, and their motivation for doing those, there is no question on what these biases were. Some of the researchers went so went quite far in bending the data such that it would fit their narrow—and racist—world view. They tried really hard to define intelligence such that it would make rich white people smarter, they were regrettably successful for far to long, but ultimately failed.
Your anecdotal evidence of high IQ parents (ugh!) having high IQ children is the same anecdotal evidence that sociologists have been describing for decades that high SES parents have high SES children, and is the main reason for why parents with high SAT scores are likely to have children with high SAT scores.
What IQ researchers discovered was basically the same thing that Marx described in 1867, class, however the eugenics were no communists, and instead of providing the simpler explanation, that society rewards the ruling elite, and wealth inherits, the eugenics went all conspiratorial and blamed other races for their perceived decline in society.
* IQ is real, measurable and heritable. The evidence for this is overwhelming.
* Nobody argues about the broad heritability of other human traits such as hair/eye color, height, athletic ability and the like.
* The argument over IQ is a consequence of terrible historical experiences with eugenics and racial discrimination. Many have adopted the quasi-religious viewpoint that IQ is not heritable to sidestep the discussion.
* As a consequence, social policy resembles the cycles and epicycles of Ptolemy's cosmology. Namely, all manner of social, economic and historical outcomes which are explained parsimoniously by understanding IQ as heritable are instead attributed to a Rube-Goldberg machine of racism, class warfare and the like.
* Accepting IQ as heritable does not, in an enlightened society, require acceptance of racism or classism, any more than people are forced to discriminate against those who, say, are genetically weaker athletes due to low relative VO2 levels.
* Social policy could be enhanced and better targeted by targeting those at the lower end of the IQ curve with subsidies such as basic income.
* Accepting IQ as real, heritable and measurable represents one of the only paths out of the present morass of corrupt political patronage programs around specific groups, just as rejection of Ptolemy's worldview enabled turning away from the demon-haunted world of religion.
If you're going to build a whole chain of logic, one that attempts to solve racism somewhere in the middle and ends with the "demon-haunted world of religion", it's useful to clearly define your terms first.
in both of those cases, as in all things genetic, expanding the ceiling is a far different matter. There is no known treatment I could have been given to enable me to run a 2 hour marathon. Similarly, there is no known way to cause a 100-IQ person to reliably test at a 140 IQ.
That said, progress is being made on artificial intelligence and genetics, so that could all change.
(I find it helpful to remember that lipstick-wearing is highly heritable despite zero genetic determination, and number of toes isn't very heritable at all despite total genetic determination.)
In particular, you can't convincingly go from discussing the seemingly profound effects acknowledging IQ heritability will have on racism, in order to avoid "demon-haunted" religious arguments, to a shrug and a handwave about genotypic (and epigenetic) effects vs. environmental effects. With due respect to your good-faith attempt to establish a logical baseline to this whole situation, the demons are haunting your argument, not those of people who'd push back on it.
It's an earlier rebuttal and you can find more precise and current ones now, but Ned Block's heritability piece is a good starting point for this stuff (you can just Google for "ned block heritable", the SERP will be dozens of links to it.)
I don't understand what is being claimed. Are you suggesting that twin studies show (or would show) that children inherit lipstick-wearing behavior from their parents, even when raised apart from them?
If this behavior is inherited, but is not genetic, what is the claimed mechanism by which it is inherited?
Causation can be determined by experiments (either "natural experiments" or intervention studies), but obviously these are both technically impossible and usually immoral to do on humans. Some fields like (…parts of) economics and medicine do experiment design properly, but many others (genetics, psychology, nutrition) just kind of ignore it and hand-wave something about P-values. This is ok if you're only using genetics to create 23AndMe ancestry charts, but it won't be once we actually have gene editing capabilities to inform.
In the case of IQ, we can identify the model through the exogenous quantity "relatedness." We know exactly how related monozygotic twins are (100%) and the expectation for dizygotic twin relatedness (50%), so we can use the fact that these quantities are known to figure out other model parameters.
Since we know that dizygotic twins are exactly half as related as monozygotic ones in the limit, we know the the genetic effect is going to be equal to 2(r_{MZ} - r_{DZ}) and excess resemblance cannot be attributable to genes, since dizygotic twins are not >50% related (on average).
Therefore, we can use it to directly figure out the fraction attributable to genetics, then we can see the excess relatedness as due to shared environments, and the residual as the unshared.
This is a pretty good high-level summary:
That this happened here is evident from the fact that you've been reduced to arguments like "IQ is genetically determined because my cat can't play chess".
https://www.etymonline.com/word/heritable#:~:text=%22capable....
https://dictionary.cambridge.org/dictionary/english/heritabi...
The Cambridge definition linked just above is particularly on point:
"The ability of a disease or characteristic to be passed from a parent or grandparent to a child through the genes"
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Yes, I know it's convenient to redefine terms like gender and heritability to fit what's politically popular. I get it. But, don't gaslight me by telling me I'm redefining the words. As you can see, I could have used this word in 1300s France and been understood as speaking about traits derived from one's parents through being their offspring.
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As for my argument about a cat playing chess, I'm just trying to give you the simplest possible example so you can see that your doctrinaire position on this subject is insane.
I'm happy to keep going on like this, because you're surfacing a lot of pernicious "race science" myths in their absolute most easily rebutted form, which is (and here truly there is no snark intended) a sort of service to the thread.
I quote, from the National Cancer Institute (a scientific institution you may have heard of): "The proportion of variation in a population trait that can be attributed to inherited genetic factors."
You're just lying or misinformed. Either way, it's starting to get hard to be civil with you.
To drive a wedge between these two concepts, he is drawing on examples like the ones put forth in Ned Block's paper, like how wearing of earrings is (or at least used to be) almost perfectly correlated with having XX chromosomes, despite the fact that being biologically female does not directly cause the wearing of earrings. Thus, according to him, your interpretation of heritability is bogus, unscientific, race science, etc.
Is this a good argument? I don't think it is. While XX chromosomes may not directly cause the wearing of earrings (or lipstick), genetics clearly are a link in the causal chain that ultimately creates the variance observed when heritability is measured. Women wear earrings because they are biologically women and we live in a culture where women wear earrings. The two factors combine to produce the effect.
The most charitable interpretation of tptacek's point is that there are other, non-genetic inputs into the directed graph of causes, that these non-genetic factors combine with the genetic factors to produce the variance, and that the non-genetic factors are morally more important. For example, clearly culture plays a role in why only women wore earrings when Block wrote his paper. This is even more clear when we see that this is no longer the case, and now it is reasonably common for men to wear earrings too.
The logical conclusion is that non-genetic factors can interact with a genetic factor to produce a difference that the genetic factor itself could not have produced. For example, you could imagine a scenario where racial prejudice and discrimination caused teachers to give up on black kids based on nothing but their race, causing them never to achieve the IQ they could have achieved if they had been given the same educational attention as a white kid. This would be a case where an IQ difference is heritable, even though the true blame lies with how people are treated based on their race.
But is that the world we live in? Given the strong heritability of IQ, and the enduring disparities that are frustratingly durable even through decades of remarkable social change, I think the onus is on the people proposing such an extra non-genetic factor to identify and measure it, in a way that can be isolated and empirically evaluated. Otherwise the argument is isomorphic to: "you're a race scientist if you think that height differences between population groups could be caused by genetics."
The extra, non-genetic factors that people would propose (socio-economic status especially) can be controlled for, and do not seem to explain the gap. Most teachers seem to value the success of racial minorities as highly, if not more highly, than other students. I think that some cultural anti-patterns in black culture could certainly play a part (like cultural pressure against being a good student), but that has been decreed to be just as verboten as the genetic hypothesis.