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<Paper uid="W00-1423">
  <Title>Coordination and context-dependence in the generation of embodied conversation</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> When we are face-to-face with another human, no matter what our language, cultural background, or age, we virtually all use our faces and hands as an integral part of our dialogue with others. Research on embodied conversational agents aims to imbue interactive dialogue systems with the same nonverbal skills and behaviors (Cassell, 2000a).</Paragraph>
    <Paragraph position="1"> There is good reason to think that nonverbal behavior will play an important role in evoking from users the kinds of communicative dialogue behaviors they use with other humans, and thus allow them to use the computer with the same kind of efficiency and smoothness that characterizes their dialogues with other people. For example, (Cassell and Th6risson, 1999) show that humans are more likely to consider computers lifelike, and to rate their language skills more highly, when those computers display not only speech but appropriate nonverbal communicative behavior. This argument takes on particular importance given that users repeat themselves needlessly, mistake when it is their turn to speak, and so forth when interacting with voice dialogue systems (Oviatt, 1995): tn -life; noisy situations like these provoke the non-verbal modalities to come into play (Rogers, 1978).</Paragraph>
    <Paragraph position="2"> In this paper, we describe the generation of communicative actions in an implemented embodied conversational agent. Our generation framework adopts a goal-directed view of generation and casts knowledge about communicative action in the form of a grammar that specifies how forms combine, what interpretive effects they impart and in what contexts they are appropriate (Appelt, 1985; Moore, 1994; Dale, 1992; Stone and Doran, 1997). We expand this framework to take into account findings, by ourselves and others, on the relationship between spontaneous coverbal hand gestures and speech. In particular, our agent plans each utterance so that multiple communicative goals may be realized opportunistically by a composite action including not only speech but also coverbal gesture. By describing gesture declaratively in terms of its discourse function, semantics and synchrony with speech, we ensure that coverbal gesture fits the context and the on-going speech in ways representative of natural human conversation. The result is a streamlined implementation that instantiates important theoretical insights into the relationship between speech and gesture in human-human conversation.</Paragraph>
  </Section>
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