Pan, Lovelett, Phun, and Rickard (2019) Systematic and random interleaving for second language learning (preprint)

Repeatedly switching between a series of to-be-learned topics, also called interleaved practice (interleaving), can improve learning over traditional, one-topic-at-a-time blocked practice (blocking). We investigated whether interleaving’s benefits for foreign language learning are facilitated by random schedules, wherein training trials follow unpredictable patterns, or systematically alternating schedules, wherein trials are predictably sorted. Students learned to conjugate Spanish verbs in the preterite and imperfect tenses and then took a 48-hr. delayed verb conjugation test. A consistently random (Experiment 1) or systematically alternating schedule (Experiment 2) did not improve learning versus blocking. However, the combination of both types – systematic alternation for study trials and randomization for practice trials – enhanced learning (Experiments 3-4). Thus, neither interleaving schedule alone appears to be sufficient; for verb conjugation skills and likely other materials involving study followed by problem-solving practice, both are needed. Interleaving’s benefits are therefore impacted by the alignment between training schedule and task type.