American IQ scores have rapidly dropped, proving the 'Reverse Flynn effect'

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?

It is not. IQ doesn’t measure a kind of intelligence which inherits, and is subject to natural selection (there is even a debate whether such intelligence exists; or at least is of any significant between individuals).

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.

The heritability of IQ is very well established, usually estimated in the 50-80% range. You are fighting an uphill battle here because even if people haven’t seen the scientific evidence this effect is so strong that virtually everybody has seen anecdotal evidence of high IQ parents having high IQ children, but just seem to assert a very heterodox and counter-intuitive position without further elaboration.

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.

I’m not fighting an uphill battle. Ever since The Bell Curve came out, there has been a slow but steady distancing of both psychological research and policy makers from the whole field of IQ research. Modern psychology couldn’t care less about on the heritability factor of IQ, and most policy makers don’t want to touch it with a 10 foot pole. Heck the SAT has even been renamed as they don’t want to be affiliated with anything resembling IQ any more.

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.

The following is my opinion, based on my research:

* 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.

People say IQ is "heritable" all the time, but it's easy to say that without giving any evidence that one understands what heritability means. Lots of things are heritable and not genetically determined, and there are things that are absolutely genetically determined that aren't really heritable.

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.

I was using "heritable" as a synonym for "genetically determined." Thanks for the clarification. To be a bit more specific, it is obviously possible to environmentally lower someone's IQ from their genetic potential. Examples include lead poisoning and denial of basic nutrition. Similarly, you can environmentally prevent someone from being able to run as fast as they might genetically have been able to by injuring their legs in various ways in childhood.

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 don't understand how your logic holds together once you concede that heritability doesn't mean "genetically determined". This is the problem with lots of arguments about "heritability" of IQ; heritability is simply the ratio of genetic effects to the total variance in a population. If we're asking whether IQ is genetic, then saying that something is "highly heritable" is simply restating the question.

(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 find it helpful to remember that lipstick-wearing is highly heritable despite zero genetic determination

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?

They are raised in a similar (or even the same) culture. The environment is a pretty powerful driver for inheritance. Genes is not the end all be all of things that are inherited across generations.

But heritability is a statistic that is specifically designed to distinguish between genetic and environmental factors. A trait whose variance has no genetic influence would have 0 heritability, unless I am missing something.

Heritability is the ratio of genetically-produced variation to total variation in some population. Overwhelmingly people who wear lipstick have a clear genetic difference from those who don't (XX vs. XY). It's a degenerate example meant to illustrate the point: heritability doesn't answer the question of genetic influence, but rather reframes it.

Ok I think I am with you now. You are saying that lipstick-wearing variation is very strongly influenced by genes (namely XX vs. XY chromosomes), and is thus highly heritable by the definition of heritability, but is somewhat paradoxical in that XX genes do not directly cause a person to put on lipstick in the same way that, say, XX genes make a person capable of bearing a child.