I think you have their point a bit backwards: they're not saying the causes of height are simple, but rather that the output is simple to measure. If you measure 5 groups and one is 20% taller than the rest, that's pretty clear evidence of something. You get one simple number, one dimension.
Intelligence is much squishier because IQ is a suspect measure at best. If a group scores 20% higher on some intelligence test, is that because of genetics? Cultural focus on learning the specific skills measured by this test? A biased test? Completely different methods of testing being falsely compared? There's no real meterstick for intelligence like there (literally) is for height, so trying to extract a number you can throw into a statistical analysis is a lot more fraught, if it's possible at all.
Intelligence is absolutely trivial to measure. You just make a huge pile of tests of mental ability, the more the merrier. It won't be very sophisticated, but you have an intelligence test. Intelligence is so easy to measure in a rough way that people have accidentally built intelligence tests when they were trying not to.
A lot of the other critiques are at least somewhat suspect: Modern intelligence tests explicitly try to use tasks that you won't train yourself that much in in daily life and that try to eg. stress working memory capacity directly without testing for other skills. There's also evidence that training for some kind of skill like strategies for n-back numbers doesn't improve performance on similar tasks using letters, for example.
Yes, it is not as good of a measure as a tape measure is, everyone knows that. But saying it's suspect and not useful is kind of like saying computer benchmarking is worthless and won't tell a crap machine from a powerful one.
> they're not saying the causes of height are simple, but rather that the output is simple to measure.
By talking about the dimensionality, they are saying both.
I agree that measuring height is easier, but I disagree that it’s causally simpler, and that is frankly what matters.
Is someone taller because of genetics or nutrition? Is there a nutrition difference because of culture, or because of racism, or because of wealth or because of IQ? Etc. Etc.
> … if it's possible at all.
It sounds like you are someone who doesn’t believe intelligence can be measured.
That's fair. I think I actually remember reading somewhere that worldwide height is catching up with European height, and what was posited to be genetic differences was actually due to nutrition. Don't have a source at hand, though.
> It sounds like you are someone who doesn’t believe intelligence can be measured.
I'm certainly skeptical about the utility of IQ or any other test as a general measure of "intelligence", when what intelligence even means is an active matter of debate.
> I'm certainly skeptical about the utility of IQ or any other test as a general measure of "intelligence", when what intelligence even means is an active matter of debate.
That's partly because it's mythologized to hell and back, and people often turn to the lack of a definition given concisely in words as proof that we don't really know it.
But, g exists, we know its nature rather well, and being able to do hang on to that measure has enabled considerable detective work as to the physical underpinnings of it.
Most simply, I think treating it as a brain performance benchmark, just like you would for a computer, doesn't go very far wrong. It's variation in the general monkey brain blueprint we're all built from, and has physical correlates that imply it as a rather general measure of the brain's performance (it's eg. linked to faster average reaction times, which would make no sense for a measure of book-learning aptitude). So, more IQ = monkey with more CPU cycles and RAM, done. Zero mythology, zero romanticism, simple.
As one analogy, you could liken it to gravity: For the longest time we knew things fell down, we could measure that speed, etc. but we didn't know why things fell down. Then we made some theories, and then new ones, and then new ones. But we don't actually know the cause and the mechanism completely. We know mechanisms of how it acts and measures of how strongly, but stuff like a quantum mechanical theory of gravity is anyone's guess at this point.
All along that journey of discovery, we still knew a fundamental fact: Somehow things fell down. That observation is the anchor. In intelligence research, that observation is g.
> 1. Intelligence is not the same as height, as one of these is low-dimensional and mechanical, and the other is high-dimensional and very complex.
Is way off. Height is influenced by a huge number of factors. It’s not just some simple genetic program.