What experimental data justifies psychologists to postulate that there is such thing as"general intelligence"?

All individuals are better in some things than in others.

What experimental data justifies psychologists to postulate that there is such thing as "general intelligence"?What experimental data justifies psychologists to postulate that there is such thing as"general intelligence"?
I don't know whether it's experimental data that led to this conclusion so much as found data, so to speak.



People tend to display a certain level of consistency in academicky-type things. So that, say, standard IQ scores tend to correlate well with performance in school.



But the notion that there's ONE form of "general" intelligence is being increasingly challenged. It's more and more clear that there are various forms of intelligence, and that far from having "general" intelligence, we have modules that process this or that particular kind of intellectual task.



So your questioning this notion is now what psychologists in general are doing.