Abductive Explanation of Dialogue Misunderstandings

To respond to an utterance, a listener must interpret what others have said and why they have said it. Misunderstandings occur when agents differ in their beliefs about what has been said or why. Our work combines intentional and social accounts of discourse, unifying theories of speech act production, interpretation, and the repair of misunderstandings. A unified theory has been developed by characterizing the generation of utterances as default reasoning and using abduction to characterize interpretation and repair. 1 I n t r o d u c t i o n When agents participate in a dialogue, they bring to it different beliefs and goals. These differences can lead them to make different assumptions about one another's actions, construct different interpretations of discourse objects, or produce utterances that are either too specific or too vague for others to interpret as intended. As a result, agents may fail to understand some part of the dialogue--or unknowingly diverge in their understanding of i t making a breakdown in communication likely. One strategy an agent might use to address the problem of breakdowns is to try to circumvent them, for example, by trying to identify and correct apparent confusions about objects or concepts mentioned in the discourse [Goodman, 1985; McCoy, 1985; Calistri-Yeh, 1991; Eller and Carberry, 1992]. The work reported here takes a different, but complementary, approach: it models how an agent can use what she or he knows about the discourse to recognize whether either participant has misunderstood some previous utterance to repair the misunderstanding. This strategy handles cases that the preventive approaches cannot anticipate. It is also more general, because our system can generate repairs on the basis of the relatively few types of manifestations of misunderstanding, rather than the much broader (and hence more difficult to anticipate) range of sources. In this paper, we shall describe an abduetive account of interpreting speech acts and recognizing misunderstandings (we discuss the generation of repairs of misunderstandings in McRoy and Hirst, 1992). This account is part of a unified theory of speech act production, interpretation, and repair [McRoy, 1993]. According to the theory, speakers use their beliefs about the discourse context and which speech acts are expected to follow from a given speech act in order to select one that accomplishes their goals and then to produce an utterance that performs the chosen speech act. Interpretation and repair attempt to retrace this selection process abductively--when a hearer attempts to interpret an observed utterance, he tries to identify the goals, expectations, or misunderstandings that might have led the to produce it. Previous plan-based approaches [Allen, 1979; Allen, 1983; Litman, 1985; Carberry, 1985] have had difficulty constraining this inference---from only a germ of content, potentially a tremendous number of goals could be inferred. A key assumption of our approach, which follows from insights provided by Conversation Analysis [Garfinkel, 1967; Schegloff and Sacks, 1973], is that participants can rely primarily on expectations derived from social conventions about language use. These expectations enable participants to determine whether the conversation is proceeding smoothly: if nothing unusual is detected, then understanding is presumed to occur. Conversely, when a hearer finds