Spaced Repetition: Why Cramming Doesn't Work (And What Does)

In the late 1880s, a German psychologist named Hermann Ebbinghaus discovered something remarkable: human memory follows a predictable decay curve. If you learn something today, you'll forget roughly 50% of it within an hour, 70% within a day, and 80% within a week - unless you review it.

But here's the key insight: each time you successfully review something, the forgetting curve flattens. After one review, you might remember 80% after a week. After a second review, the decay is even slower. Space your reviews at increasing intervals - 1 day, 3 days, 1 week, 2 weeks, 1 month - and the information moves from short-term to long-term memory.

This is the opposite of cramming. Cramming exploits short-term memory to get you through an exam, but the information evaporates within days. Spaced repetition builds permanent knowledge that stays with you for months and years. It's the difference between passing a test and actually learning the subject.

Modern spaced repetition systems (SRS) use algorithms to calculate the optimal time for your next review. The most famous is SM-2, developed by Piotr Wozniak in the 1980s, which uses your self-rated performance to adjust intervals. If you rated a card 'easy', you'll see it again in several days. If you rated it 'hard', you'll see it tomorrow.

Claritii's flashcard system uses an evolution of SM-2 that combines your performance ratings with topic-specific difficulty estimates. Cards you consistently rate highly get longer intervals. Cards you struggle with come back sooner. The result is a personalised review schedule that adapts to your actual memory, not a one-size-fits-all calendar.

To make spaced repetition work for you: start early (don't wait until the week before exams), be honest with your self-ratings (lying to the algorithm only hurts you), and do your reviews consistently (the algorithm depends on you actually studying when it schedules a session).