Dependencies of Discourse Structure on the Modality of Communication: Telephone vs. Teletype

DEPENDENCIES OF DISCOURSE STRUCTURE ON THE MODALITY OF CCI~4t~ICATION: TELEPHONE vs. TELETYPE Philip R. Cohen Dept. of Computer Science Oregon State University Corvallis, OR 97331 Scott Fertig Bolt, Beranek and Newman, Inc. Cambridge, MA 02239 Kathy Starr Bolt, Beranek and Newman, Inc. Cambridge, MA 02239 ABSTRACT A desirable long-range goal in building future speech understanding systems would be to accept the kind of language people spontaneously produce. We show that people do not speak to one another in the same way they converse in typewritten language. Spoken language is finer-grained and more indirect. The differences are striking and pervasive. Current techniques for engaging in typewritten dialogue will need to be extended to accomodate the structure of spoken language. I. INTRODUCTION If a machine could listen, how would we talk to it? Tnis question will be hard to answer definitively until a good mechanical listener is developed. As a next best approximation, this paper presents results of an exploration of how people talk to one another in a domain for which keyboard-based natural language dialogue systems would be desirable, and have already been built (Robinson et al., 1980; Winograd, 1972). Our observations are based on transcripts of person-to-person telephone-mediated and teletype-mediated dialogues. In these transcripts, one specific kind of communicative act dominates spoken task-related discourse, but is nearly absent from keyboard discourse. Importantly, when this act is performed vocally it is never performed directly. Since most of the utterances in these simple dialogues do not signal the speaker's intent, techniques for inferring intent will be crucial for engaging in spoken task-related discourse. The paper suggests how a plan-based theory of communication (Cohen and Perrault, 1979; Perrault and Allen, 1980) can uncover the intentions underlying the use of various forms. This research was supported by the National Institute of Education under contract US-NIE-C-400-76-0116 to the Center for the Study of Reading of the University of Illinois and Bolt, Beranek and Newman, Inc. II. THE STUDY Motivated by Rubin's (1980) taxonomy of language experiences and influenced by Chapanis et al.'s (1972, 1977) and Grosz' (1977) communication mode and task-oriented dialogue studies, we conducted an exploratory study to investigate how the structure of instruction-giving discourse depends on the communication situation in which it takes place. Twenty-five subjects ("experts") each instructed a randomly chosen "apprentice" in assembling a toy water pump. All subjects were paid volunteer students from the Lhiversity of Illinois. Five "dialogues" took place in each of the following modalities: face-to-face, via telephone, teletype ("linked" CRT' s) , (non-interactive) audiotape, and (non-interactive) written. In all modes, the apprentices were videotaped as they followed the experts ' instructions. Telephone and Teletype dialogues were analyzed first since results would have implications for the design of speech understanding and production systems. Each expert participated in the experiment on two consecutive days, the first for training and the second for instructing an apprentice. Subjects playing the expert role ware trained by: following a set of assembly directions consisting entirely of imperatives, assembling the pump as often as …

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