Bringing in knowledge from human discourse analysis and social cognition, we are developing autonomous agents that are capable of having a real-time face-to-face conversation with a human. These agents are human in form and communicate using both verbal and non-verbal modalities. Our current efforts focus on the integration of social and task dialogue, the ways in which people nonverbally signal topic shifts in their conversation, and studying the effectiveness of these agents on PDAs and compared to speech-only dialog systems.