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You're right to be suspicious. The studies that this figure are drawn from are generally twin studies based in wealthy Western nations. Heritability tends to in
by bsanr2 6y ago
You're right to be suspicious. The studies that this figure are drawn from are generally twin studies based in wealthy Western nations. Heritability tends to increase with wealth, economic equality, and ethnic homogeneity, all of which are unfortunately selected for in the formation of these trials. This paradigm is thought to be a gold standard, as it reduces independent variables, but it fails to capture the effects of intergroup environmental disparities in a profound way.
The range of SAT scores at a US prep academy populated with the progeny of relatively closely related families will be substantially determined by heritable differences between individuals. Outside of that, it's disingenuous and irresponsible to throw out that 80% figure as a general measure of intelligence heritability. In fact, not even the studies say that: 80% is the measure for middle-aged and senior adults. For everyone else, even their measures are substantially lower.
- Thorrez 6y ago>The range of SAT scores at a US prep academy populated with the progeny of relatively closely related families will be substantially determined by heritable differences between individuals. Can you explain that more in depth? To me that is counterintuitive. If there is a group of closely related people, I would expect their differences to be due to environment, rather than genetics, because they have similar genetics.
- bsanr2 6y agoThe opposite. They're closely related compared to the rest of the world, but still come from different families, while living in substantially similar environments, which in many way have "maxed out" advantageous factors (health, stability, stimulation, etc.). Remember that the heritable component of intelligence is polygenetic; it'd not determined by the presence of a single SNP, and two people could have similar intelligence originated in very different genetic profiles. People who are relatively closely related will have similar profiles that interact with the similar or shared environments in similar ways, meaning that the effect of small genetic differences will be more pronounced. Someone with the same "potential" for IQ, but from a different set of intelligence-related genes, interacting with the same environment might be said to have had the heritable component of their IQ become less efficacious. For example, nutrition is a component in IQ. Everyone at this school is able to drink milk and benefit from the nutrition value-add. Someone less related to the other students also attends the school; they're lactose-intolerant, but benefit from eating certain fruits native to their homeland. The school doesn't serve such fruits, but it does serve milk. The student subsequently tests at a lower IQ. I would say at this point that variation between the LP students' intelligence is likely to be more related to genetics than is the variation between their IQ and this lone student's, which has a more substantial environmental component.