After reviewing situational and demographic factors that have been argued to affect speakers' disfluency rates, we examined disfluency rates in a corpus of task-oriented conversations ( Schober & Carstensen, 2001) with variables that might affect fluency rates. These factors included: speakers' ages (young, middle-aged, and older), task roles (director vs. matcher in a referential communication task), difficulty of topic domain (abstract geometric figures vs. photographs of children), relationships between speakers (married vs. strangers), and gender(each pair consisted of a man and a woman). Older speakers produced only slightly $higher disfluency rates than young and middle-aged speakers. Overall, disfluency rates were higher both when speakers acted as directors and when they discussed abstract figures, confirming that disfluencies are associated with an increase in planning difficulty. However, fillers (such as u h) were distributed somewhat differently than repeats or restarts, supporting the idea that fillers may be a resource for or a consequence of interpersonal coordination.

When survey respondents' answers include pauses, stammers, and hedges, does this indicate that they are in danger of misinterpreting the survey question? Or are disfluencies so common in ordinary discourse that they are nondiagnostic? We analyzed respondents' first utterances after survey questions in a corpus of 42 laboratory-based telephone interviews (Schober & Conrad, 1997). Because respondents had answered questions on the basis of fictional scenarios, it was clear when their answers reflected a need for clarification. Half the respondents participated in strictly standardized interviews in which any clarification was prohibited, and half participated in more collaborative interviews in which clarification was encouraged. Results showed that respondents were more likely to pause longer, produce an um or uh, repair their utterance, and describe their circumstances in the first tum after a question was asked when answering about scenarios for which they needed clarification. Various combinations of discourse cues were also diagnostic of the need for clarification, although often only in the strictly standardized interviews.Consider this invented interchange' from a telephone interview for the Current Population Survey, which is the primary data source for calculations of the U.S. unemployment rate:

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This paper describes a prototype of a conversational system that was implemented on the Ford Model U Concept Vehicle and first shown at the 2003 North American International Auto Show in Detroit. The system, including a touch screen and a speech recognizer, is used for controlling several noncritical automobile operations, such as climate, entertainment, navigation, and telephone. The prototype implements a natural language spoken dialog interface integrated with an intuitive graphical user interface, as opposed to the traditional, speech only, command-and-control interfaces deployed in some of the vehicles currently on the market.

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