Proceedings of the Annual Meeting of the Cognitive Science Society

This paper discusses problems of synthesizing tutorial discourse in an intelligent tutoring system, Circsim-Tutor, designed to help first year medical students solve problems in cardiovascular physiology involving the negative feedback system that controls blood pressure. In order to find out how human tutors handle discourse problems we have captured both face-to-face and keyboard-tokeyboard tutoring sessions in which two of the authors ( J A M and A A R ) tutor their own students. This paper focusses on the ways in which tutors tell students that they have made an error. W e describe a classification scheme for negative acknowledgments and examine the frequency with which different types of acknowledgments occur in face-to-face and keyboard-to-keyboard sessions. Our tutors seem to make more explicit negative acknowledgments than do the tutors studied by Fox, but their acknowledgments often lead into hints that help the student continue forward in the problem-solving process. W e have collected initial data about the ways in which our tutors combine hints and negative acknowledgments.