Spaced Repetition
Spread it out over days and weeks
What the Research Says
Your brain forgets things on a predictable curve. Hermann Ebbinghaus discovered this in 1885: without review, you lose about 70% of new information within 24 hours. But each time you revisit material at the right moment — just as you're about to forget — the memory becomes stronger and lasts longer. This is the spacing effect, and it's one of the most reliable findings in all of psychology.
Evidence Base
| Study | Finding | Impact |
|---|---|---|
| Ebbinghaus (1885) | Discovered the forgetting curve — memory decays exponentially without review | Foundation of all spacing research |
| Cepeda et al. (2006) | Meta-analysis of 254 studies confirmed spacing produces stronger long-term retention than massing | Effect holds across ages and subjects |
| Dunlosky et al. (2013) | Distributed (spaced) practice rated HIGH utility across all learning contexts | One of only two top-rated techniques |
| Bjork & Bjork (1992) | "Desirable difficulties" — spacing feels harder but produces deeper learning | Explains why cramming feels effective but isn't |
Step-by-Step Method
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1
List all your topics — Write out every lesson across Biology, Chemistry, and Physics. You have around 22 lessons — this is your master list.
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2
Build a 6-week timetable — Start at least 6 weeks before your exam. Schedule 2–3 topics per day, 30–45 minutes per session.
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3
Schedule at increasing intervals — After studying a topic, schedule it again at Day 1, Day 3, Day 7, Day 14, then Day 30. Each review gets shorter because you remember more.
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4
Traffic-light after each test — After each retrieval attempt, rate the topic: Green (confident), Amber (some gaps), Red (major gaps). Reds get shorter intervals; greens can be spaced further apart.
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5
Adjust your spacing — Move green topics to longer gaps (14–30 days). Keep red topics on short cycles (1–3 days) until they turn amber or green.
When and How Often
Plan once, then follow the schedule daily. Each review session uses retrieval practice (brain dumps or self-quizzing) — not re-reading. Start 6–8 weeks before your exam to give every topic at least 4 review cycles.
Monday: Study rates of reaction for 20 minutes. Brain dump key facts: rate increases with temperature (more particles have activation energy), concentration (more collisions per second), surface area (more particles exposed), and catalyst (provides alternative pathway with lower activation energy). PAG C3 used marble chips and HCl — measured CO₂ volume over time using a gas syringe.
Tuesday: 10-minute retrieval — write down everything from yesterday. Rate: Amber (forgot the catalyst mechanism and the PAG method details).
Thursday: 10-minute retrieval. Better recall of factors. Still fuzzy on why increasing temperature also increases the rate at which particles react (not just collision frequency). Rate: Amber.
Monday: 8-minute retrieval. Now confident on all four factors and the Maxwell–Boltzmann distribution link. Can describe the marble chips/HCl PAG and identify independent, dependent, and control variables. Rate: Green. Move to 14-day gap.
Monday: 5-minute retrieval. Still solid. Quick check confirms all key content intact. Rate: Green. Final review scheduled for exam week.
Total time spent on this one topic: about 53 minutes spread over 6 weeks — far more effective than cramming it all in one sitting the night before.
Common Mistakes
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Cramming the night before — Massed practice creates short-term familiarity that fades within days. Spacing the same time across weeks produces lasting memory.
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Revising the same topic every day — Daily repetition of the same material gives diminishing returns. Space it out and use the gaps to study other topics.
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Ignoring weaker topics — It's tempting to keep reviewing what you already know. Use the traffic-light system to force yourself back to red topics.
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Starting too late — Spacing only works if you start early enough to fit in multiple review cycles. Six weeks is the minimum; eight is better.