Spaced repetition: how to review so it sticks
Cramming works for the morning of the exam and fades soon after. Spreading the same study time over days keeps it much longer. Here's how to plan it.
What it is
Spaced repetition means reviewing something again just as you're starting to forget it, and leaving a longer gap each time you remember it. The idea is old: in the 1880s Hermann Ebbinghaus measured how quickly he forgot lists he had learned, and found that spreading the relearning out saved time. A large review of later studies found the same thing across hundreds of experiments: spacing study sessions apart led to better long-term memory than massing them together (Cepeda and colleagues, 2006).
Why it works
Each time you pull something back from the edge of forgetting, the memory becomes harder to lose. A review that's too soon is easy and does little; one that's too late means relearning from scratch. The sweet spot is a review that takes a little effort. That's also why reviews should be questions you answer, not notes you reread.
A schedule to start with
For each lecture, answer your questions on it at these points. If you miss something, its next review comes back to the start of the list.
| Review | When |
|---|---|
| First | The day after the lecture |
| Second | About 3 days later |
| Third | About a week later |
| Fourth | About two weeks later |
| Then | About a month later, and before the exam |
The exact days matter less than the pattern: short gaps at first, longer ones as you keep getting it right, and a reset for anything you miss.
Fitting it into a real week
- Keep each session short: fifteen to twenty minutes of questions beats an hour of rereading.
- Start every session with what you got wrong last time.
- Mix classes in one session rather than finishing one class at a time; switching makes you choose the right idea, not just recall the last one.
- Work back from exam dates. Material for an exam in two weeks needs its first reviews this week.
Doing this with Operations Hub
Flash cards in the hub come back on a schedule like the one above, with the gap growing each time you get a card right and shrinking when you miss it. Quizzes start with your Mistake book, and your class calendar's exam dates show as countdowns so you can see what needs reviewing first. See how the parts link, with charts.
Sources
Ebbinghaus, H. (1885). Memory: A Contribution to Experimental Psychology.
Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., and Rohrer, D. (2006). Distributed practice in verbal recall tasks: a review and quantitative synthesis. Psychological Bulletin, 132(3), 354 to 380.