[rayiner]

> Statistical validity != construct validity.

Sure. But in science, we regularly postulate the existence of some construct, and confirm that construct by conducting many empirical tests that return results consistent with the existence of that construct. General intelligence is like that. We can’t see it directly. But we have myriad results that are statistically consistent with its existence.

[hirvi74]

Results consistent with the existence of a construct are not sufficient evidence for the existence of a construct. We can talk about statistical correlations till the Sun goes down, and I will not dispute that this ethereal 'g-factor' can infer minor to moderate predictions in some domains of people's lives at a population level.

However, I have one question. What evidence is there that this 'g-factor' is actually representative of general intelligence? You may not use the correlation values used to derive the g-factor to support your argument. My understanding is that correlations cannot be used to explain the general factor because the general factor should be what explains the correlations.

If you are interested, I implore you to read this blog from the statistician, Cosma Shalizi, of CMU. His explanation is far better than anything I could attempt to make.

https://bactra.org/weblog/523.html

[xyzzyz]

Sorry, what exactly do you mean by "is representative of general intelligence"? This is a very abstract statement. What does this mean in scientific, empirical terms? What kind of facts we would observe in the world where this is true? What empirical observations we'd make in the world where it's false?

[hirvi74]

> Sorry, what exactly do you mean by "is representative of general intelligence"? This is a very abstract statement.

No need to apologize. Perhaps my g is too low to describe my thoughts properly.

> "is representative of general intelligence"?

This factor that is derived from the positive correlations, g, is called general intelligence. So, g is nominally general intelligence, but is g actually what the name implies? One can take n number of positively correlated but independent things, and there will always be a some factor that can be derived from it. However, that does not mean the underlying factor is necessarily causal.

> This is a very abstract statement.

We are discussing abstract concepts.

> What does this mean in scientific, empirical terms?

That causality would be scientifically and empirically verifiable.

> What kind of facts we would observe in the world where this is true? What empirical observations we'd make in the world where it's false?

Alas, that is precisely the point I was trying to paraphrase from Shalizi. Whether g be true or false -- the result wouldn't look any different. The methodology being used cannot determine what is true nor false, and that is the crux of this entire problem.

[xyzzyz]

One can take n number of positively correlated but independent things, and there will always be a some factor that can be derived from it.

I hope you understand that your vague question cannot be seen as equivalent to this rather more concrete statement. That’s why I asked for clarification, and your patronizing comments were really not called for.

In any case, Shalizi is very wrong, probably because he is entirely unfamiliar with the literature. He is wrong on multiple accounts.

First, yes, any number positively correlated measurements will yield a common factor. However, when talking about g, this is not an artifact of how we constructed IQ tests. Shalizi says:

What psychologists sometimes call the “positive manifold” condition is enough, in and of itself, to guarantee that there will appear to be a general factor. Since intelligence tests are made to correlate with each other, it follows trivially that there must appear to be a general factor of intelligence.

But this is just not true. Tests are not made to correlated with each other. Any time anyone attempts to construct a test of general mental ability, we always find the same g factor, even if they explicitly attempt to make a battery that tries to measure distinct, uncorrelated mental aptitudes. Observe how Shalizi fails to provide a single example of a test that does not exhibit the positive manifold with other tests.

Second, unlike Shalizi, we know that g is the predictive component of the IQ tests. IQ predicts real world outcomes very well, but what is really interesting is that the predictive power of individual subtests of an IQ test is practically perfectly correlated with g-loadings of the subtest. This would be very surprising if g was just a statistical artifact.

Shalizi says

So far as I can tell, however, nobody has presented a case for g apart from thoroughly invalid arguments from factor analysis; that is, the myth.

But this is just baffling if you have any familiarity with the literature.

Whether g be true or false -- the result wouldn't look any different. The methodology being used cannot determine what is true nor false, and that is the crux of this entire problem.

That’s just not true. For example, if g was a statistical artifact, one of the hundreds of intelligence tests devised would have not exhibited the positive manifold with all the others. It would not be correlated with heritability. It would not be correlated with phenotype features like reaction time. The world where g is a statistical artifact looks much different than our world.

[TimorousBestie]

> If you are interested, I implore you to read this blog from the statistician, Cosma Shalizi, of CMU. His explanation is far better than anything I could attempt to make.

Ah, this essay is very, very good. I’m not surprised, Shalizi is a genius, but I hadn’t read this particular one before. Thanks for the link.

[rayiner]

> I will not dispute that this ethereal 'g-factor' can infer minor to moderate predictions in some domains of people's lives at a population level

The U.S. military won’t hire people below an 83 IQ to peel potatoes, because experience shows that such people can’t effectively be trained. So it’s more than just “minor” predictions.

[hirvi74]

One, you are conflating IQ and g, which are not the same thing. IQ is a proxy for the measurement of g, but it does not measure g directly.

Two, the military does not administer protected IQ exams, but rather, the ASVAB which correlates with IQ.

Three, our entire global society does not revolve around who can do what for the military.

Four, what can someone with an IQ of 84 do that one with an IQ of 83 cannot?

Five, the US military has plenty of uses for low scores. If one can't peel potatoes, then I'm sure the military would just send them out to stomp for land mines. However, Federal law is what disallows this, not the military: https://codes.findlaw.com/us/title-10-armed-forces/10-usc-se...

[xyzzyz]

And why do you think Congress has passed this law? What prompted them to micromanage the military in this manner? I encourage you to research this topic, “McNamara’s folly” will serve as a good starting keyword. Spoiler: it has everything to do with unsuitability of low IQ enlisted.

FWIW, ASVAB is an IQ test. Any intelligence researcher will tell you so, because it exhibits the usual positive manifold, you find the usual g factor in it, and it shows high correlation with other IQ test. The military doesn’t usually call it as such for political reasons, but will happily admit in private that ASVAB and WAIS measure the same thing: https://web.archive.org/web/20200425230037/https://www.rand....