1. A method for simulating behavior of a live participant in a simulation supported by a simulator, the method comprising the steps of: monitoring, by an expert system comprising a processor, the live participant for sound utterances as the live participant interacts with the simulation in a first session of the simulation; building, by the expert system, a virtual model of the live participant responsively to the monitoring; predicting a behavior of the live participant using the virtual model when triggered by a situational stimulus; comparing an observed actual behavior of the live participant in response to the situational stimulus with the predicted behavior; adjusting the virtual model responsively to a difference between the predicted behavior and actual behavior that results from the comparing; in a subsequent second session of the simulation, generating a simulated participant using the virtual model of the live participant; and providing an output representative of the simulated participant to the simulator as a stand-in for the live participant when the live participant is absent from the subsequent second session of the simulation.
2. The method of claim 1 in which the monitoring comprises monitoring conversations in which the live participant engages, and actions of the live participant.