I am curious: When do we label a person as being 'intelligent', 'smart' or 'clever'? This is subjective, and it seems unlikely that it is possible to reach a bulletproof definition. A high IQ has been used for some time, but it seems that taking IQ tests is a learnable skill as any other, see 1 (other sources contradict this fact, however, see 2). But when do we say when somebody is 'smart'? It is not rare to hear people utter 'Wow, he's really smart!'. Does he have a high IQ score? Does he know all the capitals of all countries in the world? Does he play piano extremely well, have a Ph.D. in mathematics or paint incredibly beautiful paintings?
Along the same vain, is it because we consider some tasks to be more intellectually challenging? Have they achieved things that are relatively hard to accomplish, e.g. becoming a grandmaster at chess, solving an elite sudoku in <1 min (no idea if this is reasonable), publishing groundbreaking results in science? (Just what came to my mind).
So the question is:
How do laypeople form a judgement that another person is smart or intelligent?