Here is some very interesting research from the National Institute for Health on the two different decision making processes being observed in the brain using functional MRI.

It appears that when faced with a decision between a short-term emotional reward and longer-term logical reward, two different parts of the brain are involved.

This brings to mind (no pun intended), Marvin Minsky's work on the "Society of Mind" where he posits that the entire brain is simply a bunch of independent processes which vote collectively on outcomes.

I wonder if this is how the Sim game programmers are doing it?