I think some are, some aren't. It's hard not to notice that you're different from others--that you excel scholastically, that you score high on tests if you've ever administered one, etc. You may even notice more directly, just from observing people, that they're not as intelligent as you. On the other hand, I used to hang out in a high IQ society (top 99.997 percentile), and one person there who scored about 170 at best said he never knew he was gifted until he scored high on an IQ test. I found that odd.