A systematic review of interleaving as a concept learning strategy

A systematic review was conducted into the effect of interleaving the order of examples of concepts in terms of both memory of items and transfer to new items. This concept has important implications in terms of how and when teachers present examples in the classroom. 26 studies met the inclusion criteria; a subset of 17 studies (with 32 constituent datasets) formed the basis of a meta-analysis, and the remainder were analysed within a narrative review. Memory (as tested by presenting studied items from a learned category) showed an interleaving benefit with effect sizes (Hedges’ g) of up to 0.65, and transfer (as tested by presenting novel items from a learned category) a benefit with effect sizes of up to 0.66. Interleaving was found to be of greatest use when differences between items are subtle, and the benefit extended to both art- and science-based items, with implication for practitioner decisions over how and when to apply the technique. It also extended to delayed tests. The review revealed that the literature is dominated by laboratory studies of university undergraduates, and the need for future school-based research using authentic classroom tasks is outlined