Interleaving is an approach to learning which suggests that instead of learning in blocks, the learner makes tiny, almost imperceptible steps forward in a range of (related) skills. Over time the accumulation of these steps enables much greater progress in terms of inductive learning. Interleaving allows the learner to “seat” each skill among others. In order for interleaving to work skills learned must be related in a higher-order way.
Interleaving and spacing (the effect first identified by Herman Ebbinghaus in 1885) work successfully together. [Items studied once and revisited after a delay are better retrieved longer-term than are items studied repeatedly with no intervening delay.] Spacing is often seen as an approach opposed from “massing” – or “blocking”- where one thing is learned at a time. Proponents of interleaving argue that it is more beneficial when multiple things are learned together.
The spacing effect is the finding that information that is presented repeatedly over spaced intervals is learned much better than information that is repeated without intervals (i.e., massed presentation). This effect is one of the most robust results in all of cognitive psychology and has been shown to be effective over a large range of stimuli and retention intervals from nonsense syllables (Ebbinghaus, 1885) to foreign language learning across many months (Bahrick, Bahrick, Bahrick & Bahrick, 1993).
Bjork Learning and Forgetting Lab
Robert Bjork, the director of UCLA Learning and Forgetting Lab, is a leading researcher in learning and proponent of interleaving. Here he emphasises the value of spacing:
Bjork argues that “massing” (e.g.. cramming before exams, what we would call pre-GCSE exam “interventions” [and I’d suggest the PiXL-style ones, too] in UK secondary schools) can enable students to perform well but doesn’t ensure longer-term learning/retention of information – or transferability. Instead, carefully planned spacing – whereby information from an earlier session is barely retrievable – is advocated. It seems the struggle to remember is considered by Bjork as a powerful learning tool:
One of the outcomes from Bjork’s (and other researchers) is that teachers tend to feel that blocking learning experiences is a more productive approach. The longer-term outcomes seem to actually be the opposite:
a bit of practical advice to learners and educators seems warranted: If your intuition tells you to block, you should probably interleave. (Why Interleaving Enhances Inductive Learning)
He also asserts that being forced to use memory actually shapes memory: as a learner retrieves information from memory makes the act of retrieval easier:
He’s done a great deal of research into the value of testing and quizzing in relation to developing learning and Bjork suggests that enable improved subsequent study. For teachers, Bjork emphasises the importance of questioning and quizzing (he advises lots of low-stake questioning and quizzing).
Another thing Robert Bjork advises is that students take notes just after class rather than during – forcing recall, he claims, is more effective than copying notes from a board.