I prefer to think of "smart" as a vector, I'm more interested in the dot-product with the situation at hand.
Same, but smarts is a tensor and I do a situational cross product for the hypervolume
I'm not sure you can say that it's a single dimension, and plenty of people who are very educated or have had impressive careers in one field seem out of their depth in some other area. There's definitely some skill under that all that can transfer, but you'd need to cut through a lot of other traits to try and identify it and it might not be 'smarts'. (Persistence or motivation seem like large factors.)
But this is something most people prefer to ignore because the implications are pretty big and we already had a war around that...