Thank you! If you check a few posts above you'll see the lengths we go to in our research about culture and mythology. Now, for the psychology of it... It's more feeling it than research. A lot of time, and I really mean a lot, is spent trying to pin down the specific emotion and flow to each character. It requires a lot of introspection and reflection from us.
That's why we really go ham with the introduction chapters, as each one we write is also part of the experiment through which we figure out what each character feels like.
We also constantly consult with each other about how each character would react to this or that, to try and keep it all consistent.