Towards Believable Behavior Generation for Embodied Conversational Agents

This paper reports on the generation of coordinated multimodal output for the NICE (Natural Interactive Communication for Edutainment) system [1]. In its first prototype, the system allows for fun and experientially rich interaction between primarily 10 to 18 years old human users and 3D-embodied fairy tale author H.C. Andersen in his study. User input consists of domainoriented spoken conversation combined with 2D input gesture, entered via a mouse-compatible device. The animated character can move about and interact with his environment as well as communicate with the user through spoken conversation and non-verbal gesture, body posture, facial expression and gaze. The described approach aims to make the virtual agent's appearance, voice, actions, and communicative behavior convey the impression of a character with human-like behavior, emotions, relevant domain knowledge, and a distinct personality. We propose an approach to multimodal output generation, which exploits a richly parameterized semantic instruction from the conversation manager and splits the instruction into synchronized text instructions to the text-tospeech synthesizer, and behavioral instructions to the animated character. Based on the implemented version of this approach, we are in the process of creating a behavior sub-system that combines the described multimodal output instructions with parameters representing the current emotional state of the character, producing animations that express emotional state through speech and nonverbal behavior.