IQ doesn't mean anything, except from what I've read, it possibly can be used to indicate a very low intelligence level due to possibly some kind of disorder, which would be apparently obvious already. This reminds me of a story; my friend once wanted to take an I.Q. test with me to see whose smarter. I said no, because they don't mean anything. He ended up going online and taking it anyway for 10 minutes. By the time he was done, they wanted to send it to his email, and when they sent it to his email, they said he had to pay to get his results. So I was automatically the more intelligent.
What does it mean to be gifted mentally? Presumably, the person has some inherent genetic predisposition to learn better. There are only a handful of people in the world like this (autistic people). To someone who's studied the brain and psychology, its ridiculous to say someone can be born more intelligent; they can only be born with disabilities or 'lacks'. No one is born with extra portions of the brain which makes them more smart. Tabula rasa is a blank slate given to all of us at birth. If we took Einstein out his German residence when he was born and placed him in a New York ghetto, you honestly don't believe he would be even remotely intelligent in physics later and neither do I. So, the human is more complex than we think and it won't help to make pre-set assumptions.