Proceedings of the Annual Meeting of the Cognitive Science Society

Face-to-face and keyboard-to-keyboard tutoring sessions were recorded and analyzed as a first step in building a machine tutor that can understand and generate natural language dialogue. There were striking differences between these modes of interaction. The number of turns in an hour-long session dropped and so did the length of the sentences, although the number of sentences per turn stayed roughly the same. Students contributed 3 7 % of the words in the face-to-face sessions; their share dropped to 2 5 % in the keyboard sessions. Sentence structure is simpler in the keyboard sessions. The tutors ask more questions in the keyboard sessions; they explain this as a deliberate strategy to keep the dialogue going. The tutors also use a much wider range of expressions of acknowledgement in the keyboard sessions in a deliberate attempt to communicate verbally the kind of encouragement that is often expressed nonverbally in a face-to-face situation.