While I understand that it is some sort of psych profile what do the letter stand for?
I think I might be too old to have been exposed to Myers-Briggs...
I-E(Introvert or Extrovert)
N-S(relies on intuition or relies on facts)
T-F(prefers Thinking or prefers Feeling)
P-J(emphasizes perceiving or emphasizes judging)
Don't ask me to explain all of that though; I can't quite get it myself. The most important part from a GM's or author's point of view is the descriptions of the sixteen character types provided.
INFP is an idealist. Common for sci-fi medics. McCoy was, as was the one(I forget his name) in Bab 5. Simon Tam from Firefly was more a cold-blooded thinker, but had an idealistic side that showed up so often that one might almost categorize him as an INFP. He is probably more an INTJ though.
INTJ is a walking brain-machine. Unlike a INTP who is more like a scholar, an INTJ is a Spock-like authority figure that always seems to be playing chess with the entire world. The Duke of Wellington was a typical INTJ. As was Ben-gurion. He is likly to be an Insufferable Genius if you aren't careful with him(If you want him to be an Insufferable Genius of course, then that is good writing not carelessness). But he can make a useful hero if you give him some likable qualities, like a stern code of honor, or an unbreakable loyalty to loved ones, or a soft heart underneath.
My medic I pictured as a soulful, knight-in-shinning-armor type, always sad and always worried about measuring up. The captain who is the medics big brother I pictured a Man Of Ice, who only melts around loved ones.
I would probably be an INTP though I get a different score on each test which is why I take the whole thing less seriously as an exact analysis and more for insight.