This paper describes an implemented system that generates spoken dialogue,
including speech, intonation, and gesture, using two copies of an identical
program that differ only in knowledge of the world and which must cooperate
to accomplish a goal. The output of the dialogue generation is used to
drive a three-dimensional interactive animated model -- two graphic figures
on a computer screen who speak and gesture according to the rules of the
system. The system is based upon a formal, predictive and explanatory theory
of the gesture-speech relationship. A felicitous outcome is a working system
to realize autonomous animated conversational agents for virtual reality
and other purposes, and a tool for investigating the relationship between
speech and gesture.