Unanswered Questions about Spaced Interleaved Mathematics Practice

A typical mathematics assignment consists of one or two dozen practice problems relating to the same skill or concept, yet empirical evidence suggests that there is little or no long-term benefit from working more than a few problems of the same kind in immediate succession. Alternatively, randomized experiments in the laboratory and classroom have shown that scores on delayed tests improve markedly when most of the practice problems are arranged so that (a) problems of the same kind are distributed across many assignments spaced weeks apart, and (b) problems of different kinds are interleaved within the same assignment. In this commentary, we describe these math practice strategies and suggest additional lines of research regarding students' and teachers' perceptions of the efficacy and difficulty of these strategies.