there are some I.Q test (a 4 hour battery) that are less cultural based.

just a month ago, the NYTimes science section had some samples from test, ("Pick the next in the series" or "pick the one that doesn't belong" type questions) that were used to tested people in US (of all levels) and tested people in (i forget, zambia springs to mind, but its a WAG) and by and large successful people in US (employed, completed schooling--either HS or unversity) and successful people with out schooling in the african country, (tribal leaders, sucessful hunters) scored about the same.

less successful people (employees of fast food places, or wal mart type stores, and less successful people with out education (the guys working in/on plantation at a level of virtual slavery in the african country) also faired about the same.

does a high IQ always equal success? or does hard work and success expose you to new ways of thinking? its hard to tell, but people who never studies geometry (in US or else where)and who had ( hadn't) mastered consepts of shapes/angles/progressions, faired about the same in their personal lives (as they did on the test!)

people who had mastered the concepts (either by formal education, or by the ability to think) tended to do better economically.

you don't need to study geometry to understand acute or obtuse angles (and that they are different) but if when you see them, you understantd the concept (and can pick out which angle is like the others, (or not like the others) it seems likely you are 'smarter' and better able to think.
(and the ability to think helps you get employed --or to be more successful hunting prey.. (which is just an other way to measure success!)