Spaced repetition and the science of remembering

Spaced repetition exploits the spacing effect — one of the most replicated findings in memory research — which shows that distributing study over time dramatically improves long-term retention compared to massed practice. The optimal interval for review is just before the memory would otherwise fade: reviewing too soon wastes effort, reviewing too late requires relearning from scratch. Implemented in digital systems like Anki, spaced repetition converts the science of forgetting into a technology for durable knowledge.