Anyway, most research these days supports a model based on physiological neuroplasticity - so even if brains differ chemically and physiologically, that could still be the result of experience and not (or not directly) some kind of genetic or inevitable development. We know for sure that abuse and chronic stress cause certain parts (i forget which, I believe ones involved with emotional regulation) to shrink or 'wilt'.
As far as personality goes, P is the strongest correlation but there are others. Our impulsiveness, failure to comply with certain social protocols, and difficulty functioning normally in high stimulus situations makes us rate as introverts more often. Of course, the opposite is also possible... but so is the workaholic with ADD who takes on way more than they can possibly accomplish because they don't have the self-confidence to say no, and ends up looking rather J-ish. Of course, there's also the non-MBTI trait of 'neuroticism/emotional stability', which people with ADD tend to score significantly toward the 'neurotic' end of.
Then, throw in the widely varied coping mechanisms and their far-reaching effects, and you have a ton of diversity.
How does that relate to 'giftedness'? I don't really know. I explored one idea earlier in this thread (neurological hypersensitivity) but that's all I've got. We do know that a lot of 'gifted' kids act like they have ADD when you put them in a normal classroom. The difference is, supposedly, that if you take them out and put them in a more challenging stream, they'll pick up the slack and start to really perform; whereas if they *really* have ADD, they'll struggle even more to stay on task even if it's something they're otherwise quite capable of. But IME it all depends on the level of stimulation, lol. A very animated and expressive lecturer can teach me the ins and outs of algorithm design or neurobiology, but take the exact same subject - identical slides, even - and read them in a monotone or a clumsy foreign accent, and I'll be falling asleep in minutes no matter how interesting it is.
I'm looking forward to seeing whether this is true on adderall full-time.