Interleaving

Interleaving is a study and practice technique in which a learner mixes different topics, skills or problem types together during a single practice session, rather than practicing one type repeatedly in an isolated block before moving to the next, an arrangement more commonly called blocked practice. Research by psychologists including Doug Rohrer and Kelli Taylor found that interleaved practice on mathematics problems requiring students to identify which of several formulas to apply produced substantially better performance on a later test than blocked practice, even though interleaving felt more difficult and produced worse performance during the practice sessions themselves. The technique is understood to work because blocked practice lets a learner solve each problem correctly without truly discriminating between problem types, since the type is already known from the block, whereas interleaving forces the learner to identify which strategy a given problem calls for each time, a form of retrieval practice that better prepares them for tests and real-world situations where problem type is not signaled in advance.