Affiliations: Human-Computer Interaction Institute, Carnegie Mellon
University, Pittsburgh, PA, USA. E-mail: {aleven, bmclaren, sewall}@cs.cmu.edu, [email protected]
Abstract: The Cognitive Tutor Authoring Tools (CTAT) support creation of a
novel type of tutors called example-tracing tutors. Unlike other types of ITSs
(e.g., model-tracing tutors, constraint-based tutors), exampletracing tutors
evaluate student behavior by flexibly comparing it against generalized examples
of problem-solving behavior. Example-tracing tutors are capable of sophisticated
tutoring behaviors; they provide step-by-step guidance on complex problems while
recognizing multiple student strategies and (where needed) maintaining multiple
interpretations of student behavior. They therefore go well beyond
VanLehn's (2006) minimum criterion for ITS status, namely, that the
system has an inner loop (i.e., provides within-problem guidance, not just end-of-problem feedback). Using CTAT, example-tracing tutors can be created
without programming. An author creates a tutor interface through drag-and-drop
techniques, and then demonstrates the problem-solving behaviors to be tutored.
These behaviors are recorded in a "behavior graph,"
which can be easily edited and generalized. Compared to other approaches to
programming by demonstration for ITS development, CTAT implements a simpler
method (no machine learning is used) that is currently more pragmatic and
proven for widespread, real-world use by non-programmers. Development time estimates from a large number of real-world ITS projects that have used CTAT
suggest that example-tracing tutors reduce development cost by a factor of 4 to
8, compared to "historical" estimates of ITS development time and cost. The main contributions of the work are a novel ITS
technology, based on the use of generalized behavioral examples to guide
students in problem-solving exercises, as well as a suite of mature and robust
tools for efficiently building real-world ITSs without programming.
Keywords: authoring tools, example-tracing tutors, cognitive tutors, ITS architectures, behavior of tutoring systems, programming by demonstration
