Hee! Elisabeth, love that you're analyzing the characters and their motives. It means we've got you now :)
Seriously though, there's a lot of depth to Shane and Addison (though we've seen more of Shane's than Addison's). They weren't born the way that they are, though their lives and experiences at Triptych have definitely molded them.
Fortunately, I think it's safe to say that they're still learning about themselves, too.