> I'd believe Wikipedia less than either.

That's where you make a mistake. Whatever the reason, the Wikipedia articles on the g factor, the intelligence quotient and Cattell–Horn–Carroll theory represent better what is widely accepted in the field than any other source. This somehow also turns out to be true for other academic fields.

Anyway, when source A says explicitly that source B is wrong but source B makes no such claim about source A, you should usually believe source A. But in this case you can know that the study is right by just learning for yourself what does happen to be widely accepted in the field and why it is widely accepted.

> represent better what is widely accepted in the field

How do you know this? Are you a practitioner in the field?

> when source A says explicitly that source B is wrong but source B makes no such claim about source A, you should usually believe source A

Yikes. That is scary: "You are wrong." You'd better respond or else that proves it.

"Newton is wrong." "Darwin is wrong about evolution." "Climate change scientists are all wrong." "Popper is wrong about postpositivism." "The legal system is wrong about the right to cross-examination."

You could also allow yourself to exist in a gray area where you find this interesting but do not believe you know the exact truth.