thanks sounds like you've done your share of interviewing. It would be great to hear more about your experience if you ever want to write a more lengthy blog post on this subject. I still find it very hard to predict who will make for a great employee.. provided they do ok on technical side it's still more of an intuition thing rather than process.
Rationality is more of a value than a litmus test. Those who value rationality will understand systems thinking and will tend not to focus highly on authority (either being authoritative or deferring to someone else's authority).