  PK Dick once asked "Do Androids Dream of Electric Sheep?" In video games, a
similar question could be asked of non-player characters: Do NPCs have dreams?
Can they live and change as humans do? Can NPCs have personalities, and can
these develop through interactions with players, other NPCs, and the world
around them? Despite advances in personality AI for games, most NPCs are still
undeveloped and undeveloping, reacting with flat affect and predictable
routines that make them far less than human--in fact, they become little more
than bits of the scenery that give out parcels of information. This need not be
the case. Extreme AI, a psychology-based personality engine, creates adaptive
NPC personalities. Originally developed as part of the thesis "NPCs as People:
Using Databases and Behaviour Trees to Give Non-Player Characters Personality,"
Extreme AI is now a fully functioning personality engine using all thirty
facets of the Five Factor model of personality and an AI system that is live
throughout gameplay. This paper discusses the research leading to Extreme AI;
develops the ideas found in that thesis; discusses the development of other
personality engines; and provides examples of Extreme AI's use in two game
demos.
