How do spaced repetition techniques improve long-term memory retention?

Spaced repetition works by exploiting the psychological spacing effect, where information reviewed at gradually increasing intervals is encoded more deeply into long-term memory. Each time you recall something just as you're about to forget it, the brain strengthens that neural pathway more than if you had reviewed it while the memory was still fresh. This process, called the testing effect or retrieval practice, forces active reconstruction of the memory rather than passive recognition. The technique essentially trains your brain to consolidate information into long-term storage by timing reviews to coincide with the natural forgetting curve identified by Hermann Ebbinghaus. Flashcard systems like Anki automate this by scheduling reviews based on how confidently you recalled each item, making study time far more efficient than massed practice or cramming.