Spaced repetition is the most evidence-backed learning technique that almost nobody uses correctly. Instead of studying something once for 3 hours, you review it at increasing intervals: after 1 day, then 3 days, then 1 week, then 2 weeks. Each review happens just before the memory is about to fade — which is the moment review is most effective.
The Science
Memory decays over time following a predictable forgetting curve. Each time you recall information, the decay curve resets at a higher baseline — meaning you retain more and for longer with each review. Studies consistently show 2–5x better long-term retention for the same total study time compared to massed practice (cramming).
Three Ways to Implement It
Anki (digital): Free flashcard software with a built-in spaced repetition algorithm. You rate each card (Again/Hard/Good/Easy) and Anki schedules the next review automatically. Gold standard for vocabulary, code syntax, formulas, and definitions.
Leitner System (physical): Flashcards in boxes numbered 1–5. Box 1 = daily review. Correct answers move cards up (Box 2 = every 3 days, Box 3 = weekly, etc.). Wrong answers drop back to Box 1.
Manual scheduling: For concept-heavy material, schedule reviews in your calendar: Day 1 (learn), Day 2 (review), Day 5, Day 12, Day 30.
What It’s Best For
Vocabulary, programming syntax, formulas, definitions, historical facts, and any discrete fact that needs to be recalled quickly. It’s a retention tool, not a comprehension tool — use it to cement what you’ve already understood.