I'd love your help understanding this question. I'm confused about what causal claims the Cattell–Horn–Carroll (CHC) theory of intelligence makes. As you likely know, it defines a hierarchy of three "levels of cognition" with g (measured by IQ) at the top and broad abilities below that (e.g., comprehension-knowledge, fluid reasoning, quantitative knowledge, etc.) and narrow abilities beneath those (e.g., mathematical knowledge, reading decoding, general verbal information, etc.)

But I'm confused about what the theory claims about how these are actually related in terms of what causes what.

Does the theory claim that g is merely a statistical extraction of what is in common between all of these narrow abilities (i.e., it's simply a measurement of what happens to be in common)? Or that g CAUSES these other abilities to be linked? Or something else about their causal relationships?

Thanks for your help!