  Human face-to-face conversation is an ideal model for human-computer
dialogue. One of the major features of face-to-face communication is its
multiplicity of communication channels that act on multiple modalities. To
realize a natural multimodal dialogue, it is necessary to study how humans
perceive information and determine the information to which humans are
sensitive. A face is an independent communication channel that conveys
emotional and conversational signals, encoded as facial expressions. We have
developed an experimental system that integrates speech dialogue and facial
animation, to investigate the effect of introducing communicative facial
expressions as a new modality in human-computer conversation. Our experiments
have shown that facial expressions are helpful, especially upon first contact
with the system. We have also discovered that featuring facial expressions at
an early stage improves subsequent interaction.
