At very first, no I can't tell, but given about... three, four, maybe five encounters with said person, I can judge them damn well. I tend to be able to empathize very well and get inside other people's heads in a short amount of time.
Have you ever known exactly what kind of person someone is, and insisted it over and over to someone else, only to be rejected as a fool, and later to be proven overwhelmingly correct?
~kov.