Myers-Briggs obviously doesn't represent some fundamental truth about how personalities vary, but I'm willing to bet that no matter how you ask people questions

Myers-Briggs obviously doesn't represent some fundamental truth about how personalities vary, but I'm willing to bet that no matter how you ask people questions about themselves there will be useful conclusions to draw. Certainly some people are more sociable than others, some more detail-oriented than others, and vary on any other traits you care to name. Given that they are all probably hopelessly correlated with each other, and with whatever variables are actually controlling things underneath, it would be difficult to come up with a test that didn't say something. On a far more speculative note, I bet most of the complex parts of the brain don't vary much between people, or at least don't play into personality much. That's not backed up by anything though, just an idle thought.