Scientists measure the effect of genes on IQ within the modern Western world by observing the IQ correlation between identical twins raised apart. Because in adulthood, this correlation is very high (about +0.8) within Western countries, adult IQ is said to be 80% heritable within Western countries, and how you were raised is said to have only a tiny effect on adult IQ. Critics claim the studies are flawed because adoption placement bias results in even separated twins growing up in somewhat similar homes. However whatever variables such homes are slightly similar in are found to have little if any effect on adult IQ, leaving the critics without a leg to stand on. But the critics can’t see their error.
If the correlation between genetically “identical” people raised in different homes quantifies the effect of genes on IQ, then the correlation between unrelated people raised in identical homes quantifies the effect of “shared environment” on IQ. The term shared environment refers to environments that differ between families, as opposed to non-shared environment which refers to environments that differ within families. The correlation between unrelated people raised together is +0.25 in childhood, but only -0.01 in adulthood, suggesting shared environment has virtually no effect on adult IQ.
The tiny correlation between unrelated people raised together has proved very embarrassing for those who minimize the importance of genes. They dismissed the high correlation between identical twins raised apart by arguing that kids end up being adopted into homes similar to their biological family and thus experience similar environments, but if that’s true, how do they explain the dismal IQ correlation between unrelated people raised together?
There’s an entire generation of university students that were duped and brainwashed by the HBD denial of Stephen Jay Gould and these are the voices that dominate academia, the media, and to a large extent the internet. They think they are very enlightened, but the truth is they’re just mindlessly parroting the pseudo-intellectualism of the liberal so-called intelligentsia. To quote Christopher Langan, the stupid person doesn’t know that he’s stupid, and therein lies his stupidity.