Radiant AI is Bethesda proprietary software which scripts NPCs (non playing characters) with a predetermined list of goals, eg what time they will wake up, the route they walk to work, what work they will do, what tools they will use, when to break for lunch, where they go to eat lunch, drink, rest etc. nothing unusual there, and only five or six types of tasks that could be assigned to each NPC. But where Radiant AI excels and where the fun really starts, is how they achieve these tasks and how they react if their routine is disturbed. Again a predetermined script assigns characteristics to each NPC eg. their aggression levels, fighting skills, and the really really innovative bit, ..........decision making script routines.For example during game development one NPC was given a rake and the goal "rake leaves", another was given a broom and the goal "sweep paths," and this worked smoothly. Then the dastardly Bethesda programmers swapped the broom and the rake, so that the raker was given a broom and the sweeper was given the rake. Result!?, one of them killed the other so he could get the proper item to complete his goal. The murderer's aggression level was so high, it was a logical decision (set by the software routines) that giving his fighting skills, murdering his counterpart was a scripted necessity to continue his assigned overiding goal.Skyrim:For the upcoming "Skyrim" Bethesda went back to the drawing board and rewrote every major system powering the gameplay experience. The result is the newly dubbed "Creation Engine and Kit" characters having much more defined individual personalities, more attuned to your presence and more inclined to help depending on your relationship with them. This time around if you're good friends with a particular NPC and barge into their house during the middle of the night, they may offer you lodging rather than demand you leave the premises.