[samhw]

Hmm, I don't think that's true. I score incredibly highly on the 'verbal IQ' segment of the test, and anecdotally I seem to give people the impression of intelligence, but in the mathematical segment of the test I score about as highly as a potted plant.

Unless you've ever independently (non-circularly) corroborated your 'idea of how smart someone is', my guess is that it just serves as a proxy for qualities like academic education (which != intelligence), social class, similarity to yourself, &c.