The Myres Briggs test is a playground for driving people insane. I know I'm not unique in this, but I have two basic modes, one introvert and one extrovert. When I am working on technical, mathematical, or analytic problems, I score very high on the introvert scale. If I have been talking with friends recently, very high extrovert. I'm not saying Myres Briggs should be done away with (though a few psychologists I know think so), but it really depends on the mood you're in when you take it.
But back onto the original theory, I think personality plays a big role in training. If you are an extrovert and like to train in groups, you don't want to wait for your buddies to finish a 20 rep squat while you watch.