Directed Improvisation by Computer Characters

We present a directed improvisation paradigm, in which computer characters improvise a joint course of behavior that follows users' directions, but also engages and entertains users with the novelty, life-like qualities, and performance properties of their improvisations. We present requirements for improvisational characters that differ from the usual requirements for conventional computer agents and present an architecture that is designed to meet the new requirements. Two implemented characters exploit some of these architectural features to meet simple versions of the requirements. Finally, we illustrate the utility of improvisational characters for a variety of applications related to the arts and entertainment, including a suite of interaction modes in our testbed environment, a Virtual Theater for Children.