Spaced repetition is a learning technique where you review material at increasing intervals over time, rather than all at once. It's based on Hermann Ebbinghaus's forgetting curve — a 19th-century discovery that still holds up under modern neuroscience — which shows that memory decays predictably after learning, and each review resets and extends the decay curve.
The result: you review material just before you're about to forget it. This is the most efficient use of revision time — and it produces dramatically better long-term retention than any amount of re-reading or cramming.
The Forgetting Curve
Ebbinghaus studied his own memory by learning lists of nonsense syllables and testing recall at different intervals. He found that without review, people forget roughly 50% of new information within a day, and up to 90% within a week.
% of information retained after a single learning session.
How Spaced Repetition Fights Forgetting
Each time you review material, the forgetting curve resets — but the new curve is shallower. The information is retained for longer before it starts to decay. Review it again, and the interval extends further. After 4–5 well-spaced reviews, most students can retain information for months or years.
Spaced Repetition vs Cramming
Cramming (massed practice) produces strong short-term recall. Students who cram the night before often feel well-prepared — and they might perform adequately if the exam is the next morning. But the information fades rapidly. In subjects that build on prior knowledge (mathematics, sciences, languages), this is catastrophic.
Spaced practice produces slower initial learning — it feels less efficient — but delivers dramatically stronger long-term retention. The research is consistent: distributed practice over time outperforms massed practice in almost every study that has measured it.
How to Use Spaced Repetition Without Complex Software
You don't need a complex algorithm to benefit from spaced repetition. The simplest system that works:
Make flashcards for every key fact or concept. Review the full deck after 1 day, then 3 days, then 1 week. Study Buddy's flashcard tool is built for this.
Enter your exam date into Study Buddy. The planner auto-generates revision sessions using spaced intervals, working backwards from your exam.
Sort flashcards into: 'Know it', 'Shaky', 'Don't know'. Review 'Don't know' daily, 'Shaky' every 3 days, 'Know it' once a week.
Don't study one subject all week. Rotate between subjects so each one gets reviewed at spaced intervals naturally.