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<Paper uid="W97-0620">
  <Title>Dialogue Strategies for Improving the Usability of Telephone Human-Machine Communication</Title>
  <Section position="10" start_page="116" end_page="118" type="concl">
    <SectionTitle>
6 Discussion
</SectionTitle>
    <Paragraph position="0"> By analizing the Dialogos corpus, we identified some topics that require further work.</Paragraph>
    <Paragraph position="1"> The first one is related to the need for goal management: in the task domain of Dialogos the goal is fixed during all the dialogue, but that is a simplification of the travel inquiry domain, introduced to control the complexity of interaction in order to meet the real-time requirement. However, we believe that the ability of the dialogue system to support goal management would greatly increase the naturalness of dialogue, as the work by (Allen et al., 1996) shows.</Paragraph>
    <Paragraph position="2"> The second problematic issue is related to the impact that recognition errors have on the user be- null haviour. By examining the Dialogos corpus we collected evidence that some critical situations occur when the users make experience of repetitive recognition errors. The recognition errors seem to cause a cognitive overload in the users that influence their degree of co-operativeness. In our task domain most of the recognition errors occur during the recognition of departure city and arrival city. When users are asked to repeat a city name that was misrecognized by the system, some of them modify their way of speaking: they repeat the name louder, or spelt it, or even accept a misrecognized name proposed by the system. In this corpus 15.1% of the dialogues failed for users' errors. Similar behaviour has been described in (Bernsen, Dybkjaer, and Dybkjaer, 1996).</Paragraph>
    <Paragraph position="3"> During the evaluation of the Dialogos corpus we classified the users' errors into two main classes: 1. the user confirmed a task parameter value that derived from a misrecognition (76% of the users' errors) after having experienced several recognition errors; 2. the user accepted a task parameter derived from a word that was inserted by the recognizer and interpreted by the parser (24%).</Paragraph>
    <Paragraph position="4"> We applied the above classification in a different experimental set-up: in May 1996 a laboratory test was designed to study the reaction of users to different speech technologies and dialogue strategies applied to the railway information domain. 48 naive subjects took part in the experiment: they were equally distributed by sex; the age range was from 18 to 62 years. The subjects of this experiment called Dialogos and another spoken dialogue system. Each of them played two different predetermined scenarios with each system; after the trial, they were interviewed (the discussion of this experiment may be found in (Billi, Castagneri, and Danieli, 1997)). By analyzing the 96 dialogues between Dialogos and the experimental subjects, we found that the occurrence of users' errors could be classified into the two classes described above, that is users' errors were always condomitant with substitutions or insertions in the best-decoded sequence. In particular, in both the experiments subjects reaction to recognition errors was characterized by an alteration in the way of speaking. In the interviews collected in the second experimented, the subjects that made errors expressed the fatigue in experimenting repetitive recognition errors. However, we hypothesize that the non-cooperative behaviour may be partially due to the artificial experimental conditions: we are planning to experiment the current version of Dialogos in a real environment with users that really need to take trains for travelling all around Italy, and that will use the system for having timetable information.</Paragraph>
    <Paragraph position="5"> While there are clearly many aspects in which our current approach requires further work, we may claim that speech is a viable interface if we provide spoken systems with robust dialogue management.</Paragraph>
    <Paragraph position="6"> We have shown that the use of contextual information in different system modules may reduce the recognition errors, and increase the usability of telephone human-computer dialogue.</Paragraph>
  </Section>
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