Illustrating Principled Design: The Early Evolution of a Cognitive Tutor for Algebra Symbolization

This paper provides an illustration of the principled design of an interactive learning environment. It provides a view of the early stages of this process where design, testing, and redesign are most critical. The long term goals of principled design are twofold: (1) to create a system that can be convincingly demonstrated as an effective and practical learning aid and (2) to provide a replicable account of how and why the system is effective. A principled design is one that is both theoretically guided and empirically supported. A principled design is guided by a set of theoretical principles and specific pedagogical hypotheses (Anderson, Corbett, Koedinger & Pelletier, 1995: Koedinger & Anderson, 1993). It is informed by user testing early and often. The design process is iterative: theory, design, test, redesign. Tests that fail lead first to redesign and then. if principled redesigns fail. to changes in the theory. It should be the natural expectation of the field that no Interactive Learning Environment will be fully effective in its initial implementations and that early demonstrations of limitations have a positive. not a negative, bearing on the value of the final system. The only systems immune to some failure are ones that ure never tested. Unfortunately, these are all too common. (For example. Corbett. Koedinger and Anderson (in press) report that only 25% of the papers at recent ITS conferences include any kind of empirical evaluation.) We describe the design of a particular kind of intelligent tutoring system called a cognitive tutor (Anderson, Corbett, Koedinger & Pelletier. 1995). In addition to employing artificial intelligence techniques, cognitive tutors have the defining feature of containing a psychological model of the cognitive processes behind successful and near-successful student performance. This cognitive model provides the core functionality. The cognitive model is used by a