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.

“Heritability” may or may not have anything to do with genetics or biology. For example socioeconomic status and proximity to zip code are also heritable.

> “Heritability” may or may not have anything to do with genetics or biology. For example socioeconomic status and proximity to zip code

Twin studies [1]. Different parents, socioeconomic statuses, possibly countries. Sustained significant statistical effects. That’s the genetic component of intelligence.

[1] https://www.nature.com/articles/mp2014105 first four references

Twin studies provide evidence that there is a biological component to intelligence. They do not tell us how much more biologically likely it is for high-IQ parents to produce high-IQ kids—which is usually what people mean by the “heritability” of IQ.

In plain English: the twin studies show us how similar twins are, but they don’t tell us how true the movie Idiocracy is.

> do not tell us how much more biologically likely it is for high-IQ parents to produce high-IQ kids

"Individual differences in intelligence tend to cluster in families" [1].

There are studies which include "parents in a twin design." They found "no significant shared environmental influence [between the adoptive and non-adoptive children]: all variance could be explained by additive genetic factors and environmental factors that are not shared by children raised in the same family" with "significant genetic transmission for intelligence...found at all ages" (§ 1.3).

[1] https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&d...

But are the parents actually high-IQ, or do they exhibit some other set of characteristics that correlate with high-IQ children?