AI Difficulty Setting Question

[Edi]

When you make a game with all human players and then turn most of them to AI control, what difficulty setting does the game assign them? A specific difficulty, or randomly selected between Easy, Normal, Difficult and Impossible? I'm a little curious about this, as I mostly play SP or co-operative hotseat games with a friend, and we'd like to see the AI not screwing itself up the butt with those death/turmoil/misfortune 3 combos.

I'm also wondering because in an SP game I'm in the middle of right now where I did this, most of the AI nations I've seen are rather pathetic, but a few are doing really well (namely Arco, which is not a surprise, BE Ermor and Abysia). It seems some good nations I've seen play well are simply sitting and twiddling their thumbs while the others are kicking arse all over the place.

Also, it would be nice to be able to select some default AI level human players revert to when they become computer controlled.

Any thoughts?

Edi