Abstracl;: If human-computer interaction is to be effective, it is vi~al that there are opportunities to check on understanding, and repair that understanding when it fails. This paper discusses this idea of repair in human-computer interaction, and provides a number of examples of different types of repair work in an interactive explanation system. 1.

: It is important for students to understand why they made errors and what would be the consequences of these errors in problem solving in order to correct and prevent them from repeating. In this paper, we present a behavior simulation which reflects an error a student made in solving a mechanics problem. We call the simulation SER which stands for "Simulation for Error-Reflection." Our prototype system changes a value of a velocity or acceleration of an object by using the erroneous equation, and generates a simulation with the changed value. The difference between SER and normal-simulation illustrates the error more intuitively for students than abstract formula representations. Therefore, the SER is one of the more promising methods to help students recognize and correct their errors themselves. This paper describes a framework of the SER and error-remediation with it, and the effect for remediation is also discussed. 1 Introduction It is important for students to understand why th...