[sbierwagen]

With AI, there's also the problem of being more accurate than you want to be. A triple-A title like MW3 or Skyrim is essentially "a movie you walk through". NPCs have lines, they follow a script.

You could easily have NPCs that run a little life simulation, (like in the early versions of Oblivion) but then you have the problem of NPCs going off the script. If you accurately simulate mental states, and some villager rolls a 1 on the d2000 mental state die, then proceeds to kill all the plot-critical NPCs in their village? Now you've got a more realistic, yet completely broken, game.

[sycren]

If you were to accurately simulate mental states, there would need to be some kind of cause like the player murdering all the NPC's friends in front of them to end up on 1 rather than a randomly generated value