Mental State Recognition and Communicative Eeects

Speech acts in natural language dialogues can be regarded as intentional acts performed by a dialogue participant to innuence the relevant aspects of the mental state of a recipient. In this paper, a framework is discussed for deriving the beliefs and intentions of a speaker from a certain speech act. To this end, the notion of a speech act is replaced by the formal notion of a communicative act. A communicative act is expressed in terms of prosodic and textual features of the utterance and connected by means of default rules to the conditions that must be fulllled by a speaker in order to perform the act felicitously. To indicate preferences among sets of conditions, hierarchic default rules were introduced. The conditions are expressed in terms of beliefs and intentions of the speaker and the hearer and may be compared with Searle's felicity conditions on speech acts. It is argued, though, that some of the conditions can be derived from a formalization of general principles of rational behaviour in dialogues. Communicative eeects were computed on the basis of the consequences of the observed communicative act and the actual circumstances of the act.