When and Why Does Mastery Learning Work: Instructional Experiments with ACT-R "SimStudents"

Research in machine learning is making it possible for instructional developers to perform formative evaluations of different curricula using simulated students (VanLehn, Ohlsson & Nason, 1993). Experiments using simulated students can help clarify issues of instructional design, such as when a complex skill can be better learned by being broken into components. This paper describes two formative evaluations using simulated students that shed light on the potential benefits and limitations of mastery learning. Using an ACT-R based cognitive model (Anderson & Lebiere, 1998) we show that while mastery learning can contribute to success in some cases (Corbett & Anderson, 1995), it may actually impede learning in others. Mastery learning was crucial to learning success in an experiment comparing a traditional early algebra curriculum to a novel one presenting verbal problems first. However, in a second experiment, an instructional manipulation that contradicts mastery learning led to greater success than one consistent with it. In that experiment learning was better when more difficult problems were inserted earlier in the instructional sequence. Such problems are more difficult not because they have more components but because they cannot be successfully solved using shallow procedures that work on easier problems.