Is spaced repetition effective for language learning?

Is spaced repetition effective for language learning? Yes, and it is one of the most replicated findings in memory research. The spacing effect (reviewing something at growing intervals instead of cramming it) held up across 317 experiments in Cepeda and colleagues' 2006 meta-analysis, and Dunlosky's 2013 review rated distributed practice among the two highest-utility study techniques of the ten it tested. Vocabulary is the ideal case: single words are exactly the kind of discrete facts that spacing locks in. The honest limit is that spacing only decides when a word comes back. It does not teach you to speak, so it works best paired with real input and conversation, not on its own.

In practice the schedule does the remembering, so you are not re-cramming the same list. The catch is that it only pays off if the reviews actually happen and the cards are worth reviewing. For the fuller picture, here is the evidence on whether spaced repetition works and where it falls short.