Spaced Repetition: The Science of Remembering What You Study
A practical guide to spaced repetition — why it beats cramming, how the SM-2 algorithm schedules reviews, and how to use it well.
Spaced repetition is a memory technique based on a simple insight: you remember things better when you review them at intervals that gradually increase over time. The first review should happen within 24 hours of learning. The second review a few days later. Then a week later. Then two weeks. Each successful recall pushes the next review further into the future.
The alternative — reading your notes the night before an exam — is called massed practice or cramming. Research consistently shows that cramming produces short-term retention (enough to survive a 9 AM exam) but almost zero long-term retention. Spaced repetition, by contrast, encodes information into long-term memory. This matters for professional exams, licensing tests, and cumulative courses where earlier material feeds into later material.
The SM-2 algorithm, first developed by Piotr Wozniak in 1987 and used in apps like Anki, calculates the optimal interval for each flashcard based on how you rated your recall. If you rated a card "easy," the next review is pushed far into the future. If you rated it "hard," the card reappears the next day. ExamWiz's flashcard system uses this same algorithm — you do not need to think about scheduling. The system handles it.
For best results with spaced repetition: (1) Keep flashcards atomic — one fact per card, not a paragraph. (2) Use images or diagrams on the front of the card when possible — visual memory is stronger than text memory. (3) Review your due cards every day, even if only for 10 minutes. Missing a day does not break the system, but it adds cards to your backlog. (4) Add new cards gradually — adding 50 cards a day will quickly create an unmanageable review backlog.
For medical students specifically, spaced repetition is most effective for: drug mechanisms and side effects, anatomical structures and their functions, laboratory reference values, and diagnostic criteria. For these categories, the volume of individual facts is too high for any other study method to be practical.
