Abductive Explanation of Dialogue Misunderstandings

Abductive Explanation of Dialogue Misunderstandings Susan McRoy and Graeme Hirst Department of Computer Science University of Toronto Toronto, Canada M5S 1A4 Abstract To respond to an utterance, a listener must interpret what others have said and why they have said it. Misunderstandings oc- cur when agents differ in their beliefs about what has been said or why. Our work com- bines intentional and social accounts of dis- course, unifying theories of speech act pro- duction, interpretation, and the repair of misunderstandings. A unified theory has been developed by characterizing the gen- eration of utterances as default reasoning and using abduction to characterize inter- pretation and repair. 1 Introduction 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 interpre- tations 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 it-- making a breakdown in communication likely. One strategy an agent might use to address the prob- lem of breakdowns is to try to circumvent them, for example, by trying to identify and correct appar- ent 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 complemen- tary, 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 ap- proaches cannot anticipate. It is also more general, because our system can generate repairs on the basis of the relatively few types of manifestations of mis- understanding, rather than the much broader (and hence more difficult to anticipate) range of sources. In this paper, we shall describe an abduetive ac- count of interpreting speech acts and recognizing misunderstandings (we discuss the generation of re- pairs of misunderstandings in McRoy and Hirst, 1992). This account is part of a unified theory of speech act production, interpretation, and re- pair [McRoy, 1993]. According to the theory, speak- ers 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 accom- plishes their goals and then to produce an utter- ance that performs the chosen speech act. Interpre- tation and repair attempt to retrace this selection process abductively--when a hearer attempts to in- terpret an observed utterance, he tries to identify the goals, expectations, or misunderstandings that might have led the to produce it. Previous plan-based ap- proaches [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 in- sights …

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