As far as I know, the Myers-Briggs was effectively thought up by a couple of women, who looked at words and their meanings and applied them to people, such as "thoughtful" and "introverted" etc, and came up with a bunch of questions that would elicit answers about these words. The key point is that it was all done from scratch, and has not been tested scientifically in any way, as far as I know. They constructed a particular world view themselves. I'm not saying its totally innacurate, just that it is a blunt instrument.