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Small-Scale Question Sunday for May 7, 2023

Do you have a dumb question that you're kind of embarrassed to ask in the main thread? Is there something you're just not sure about?

This is your opportunity to ask questions. No question too simple or too silly.

Culture war topics are accepted, and proposals for a better intro post are appreciated.

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I realise this may come across as stirring the pot, but I hope I've been here long enough to have earned the benefit of the doubt.

In the context of the HBD debate, could someone please ELI5:

  • The concept of heritability and how it relates or doesn't relate to genetic causes of individual or group differences. I am aware of the "books at home" example. Is that all there is to it?

  • What precisely g is?

  • Steelman(!) Turkheimer's position. No, I don't want to hear about his politics.

  • Roughly summarise the position of Kirkegaard et al.

This whole debate always gets technical so quickly that I very often just get lost. I don't want to rehash the arguments here, I would like to understand the basics. But the waters are often so damn muddied (purposely so, I suspect) that it's very hard to get a grasp of what people are even fighting about.

I am aware of the "books at home" example. Is that all there is to it?

I think twin adoption studies that control for socioeconomic class show heritability cannot be boiled down to environmental stuff the parents do.

What precisely g is?

That one also always sounded like vodoo to me. I also don't like various statistical tricks they play to normalize IQ, though that one cuts both ways as far as political correctness is concerned.

I think twin adoption studies that control for socioeconomic class show heritability cannot be boiled down to environmental stuff the parents do.

So, Wikipedia defines heritability as "a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of heritability can be expressed in the form of the following question: "What is the proportion of the variation in a given trait within a population that is not explained by the environment or random chance?"

But in every single HBD discussion, there is someone claiming that heritability and genetic influence are not identical. They usually bring up something clearly environmental, such as "having books at home" and claim that this would also be heritable. I do think it has something to do with how many environmental circumstances such as parental behaviour might themselves be influenced by the parents' genes. But this doesn't seem like a refutation of genetic impact to me.