Speech Dialogue With Facial Displays: Multimodal Human-Computer Conversation

SPEECH DIALOGUE WITH FACIAL DISPLAYS: MULTIMODAL HUMAN-COMPUTER CONVERSATION Katashi Nagao and Akikazu Takeuchi Sony Computer Science Laboratory Inc. 3-14-13 Higashi-gotanda, Shinagawa-ku, Tokyo 141, Japan E-mail: { nagao,t akeuchi} @csl.sony.co.j p Abstract 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 multi- plicity of communication channels that act on mul- tiple modalities. To realize a natural multimodal dialogue, it is necessary to study how humans per- ceive information and determine the information to which humans are sensitive. A face is an in- dependent communication channel that conveys emotional and conversational signals, encoded as facial expressions. We have developed an experi- mental system that integrates speech dialogue and facial animation, to investigate the effect of intro- ducing communicative facial expressions as a new modality in human-computer conversation. Our experiments have showen 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 sub- sequent interaction. Introduction Human face-to-face conversation is an ideal nmdel for human-computer dialogue. One of the major features of face-to-face communication is its mul- tiplicity of communication channels that act on multiple modalities. A channel is a communica- tion medium associated with a particular encod- ing method. Examples are the auditory channel (carrying speech) and the visual channel (carry- ing facial expressions). A modality is the sense used to perceive signals from the outside world. Many researchers have been developing mul- timodal dialogue systems. In some cases, re- searchers have shown that information in one channel complements or modifies information in another. As a simple example, the phrase "delete it" involves the coordination of voice with ges- ture. Neither makes sense without the other. Re- searchers have also noticed that nonverbal (ges- ture or gaze) information plays a role in set- ting the situational context which is useful in re- stricting the hypothesis space constructed dur- ing language processing. Anthropomorphic inter- faces present another approach to nmltimodal di- alogues. An anthropomorphic interface, such as Guides [Don et al., 1991], provides a means to realize a new style of interaction. Such research attempts to computationally capture the commu- nicative power of the human face and apply it to human-computer dialogue. Our research is closely related to the last ap- proach. The aim of this research is to improve human-computer dialogue by introducing human- like behavior into a speech dialogue system. Such behavior will include factors such as facial expres- sions and head and eye movement. It will help to reduce any stress experienced by users of comput- ing systems, lowering the complexity associated with understanding system status. Like most dialogue systems developed by nat- ural language researchers, our current system can handle domain-dependent, information-seeking di- alogues. Of course, the system encounters prob- lems with ambiguity and missing intbrmation (i.e., anaphora and ellipsis). The system tries to re- solve them using techniques from natural language understanding (e.g., constraint-based, case-based. and plan-based methods). We are also studying …

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