Wait, flesh this thought out? Twin studies were the dominant methodology of the 1970s-1990s, until molecular genomics --- and genetic studies with controls for family relations demolished their heritability estimates. You just wrote a sentence that implies a straight line of progress on understanding this (weirdly, giving a 70s-vintage point in one direction along with a 2010s-vintage point in the other), but it's the opposite (there's a whole thing about this, the "missing heritability problem").

"Go look up twin studies" is a very strange thing to tell someone on a message board in 2026. It's like saying "go look up phlogiston".

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estearum a day ago | parent [-]

Identical twins reared together: .85 correlation in IQ

Fraternal twins reared together: .55 correlation in IQ

Identical twins reared apart: .75 correlation in IQ

And the genetic correlation grows as children age.

No, genetic studies did not "demolish" heritability estimates, they set a floor on them. Genetic studies do not and cannot (currently) predict all phenotypic outcomes, they set the floor on how much variation can be caused by genetic differences.

The genetic predictions don't even directly contradict, never mind demolish, the twin study findings.

The "missing heritability problem" is only a problem if one believes our genetic analysis techniques are comprehensive, but we already know they're not. For example, current methods are extremely limited in detecting gene-gene interactions, which we have good reason to suspect are widespread (otherwise making new genetic drugs would be trivial).

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tptacek a day ago | parent [-]

Even hereditarians don't believe the .85 number anymore. I think you probably want to do some more recent reading.

This has come up a bunch on HN and I don't want to rehash dozens of earlier comments, but the search bar will give you plenty of cites.

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estearum 20 hours ago | parent [-]

Yes, the .85 is probably at the upper end of the estimate. The genetic studies are the conceivable floor.

I'm not sure what you mean by "hereditarian" given that even the genetic studies obviously point to significant heritability.

This is always a funny conversation because on the one side you have people saying "intelligence is both heritable and correlated with nearly every outcome we care about."

On the other hand you have people saying "nuh uh! It's only... medium-high heritability and medium-high correlation with other positive outcomes," as if it makes any material difference to any downstream question.

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tptacek 19 hours ago | parent [-]

It's not "the upper end of the estimate"; it's no longer the estimate. Meanwhile, hereditarians believe in strong genetic determinism for behavioral attributes. I think you should probably be more familiar with this field and its terms before being this confident about your numbers.

Again, the search bar will avail, but the answers you're giving here are very early-90s.

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estearum 18 hours ago | parent [-]

Most people who you'd (clearly) slur as hereditarians don't actually believe in "strong genetic determinism."

Why don't you just share what your estimate is?

Is it zero?

	▲	tptacek 18 hours ago \| parent \| next [-]
		I don't know how we can continue discussing at this point, since "hereditarian" is not a slur (it's how many in the field would describe themselves). You either follow this research or you don't, either is fine, but it's not reasonable to attack other people for being familiar with it. It's totally OK if we're just not going to persuade each other or develop any productive ideas in this thread! I've said all I originally wanted to say.
	▲	scott_s 16 hours ago \| parent \| prev [-]
		A good place to start: https://news.ycombinator.com/item?id=46195226. (The submitter should be familiar.)