The forgetting curve
Over a century ago, Hermann Ebbinghaus showed that memory decays predictably: without review, we lose a large share of newly learned information within a day or two, and most of it within a week. This is the forgetting curve, and it's why last-minute cramming fades so fast.
The good news is that each time you review something just as you're about to forget it, the curve resets and flattens - you forget more slowly next time. Spaced repetition is simply doing this on purpose.
What spaced repetition is
Spaced repetition means revisiting material at growing intervals rather than all at once. Instead of studying a topic five times today, you study it today, again tomorrow, then in three days, then a week later, then a few weeks after that.
Each successful review tells your brain the information is worth keeping and pushes the next review further out. Difficult items come back more often; easy ones fade into the background. Over time you spend less effort remembering more.
How to schedule your reviews
You don't need software, though it helps. A simple, effective schedule for a new topic:
- ✓Review 1: the same day you first learn it.
- ✓Review 2: the next day.
- ✓Review 3: about three days later.
- ✓Review 4: about a week later.
- ✓Review 5: two to three weeks later, then monthly.
- ✓Bring an item back sooner whenever you get it wrong, and push it further out when you get it right.
Spaced repetition + active recall
Spacing works best when each review is an act of retrieval, not re-reading. So at every scheduled review, test yourself - answer questions, do a quiz, recall from a blank page - rather than passively skimming your notes.
This pairing is the engine behind flashcard apps and every serious revision plan: retrieve (active recall), wait (spaced repetition), retrieve again. Done consistently, it's the most reliable way to remember large amounts of material for months.
Common mistakes to avoid
- ✓Cramming everything the night before instead of spacing it over days and weeks.
- ✓Reviewing by re-reading rather than testing yourself at each interval.
- ✓Reviewing everything at the same frequency instead of spacing easy items further out.
- ✓Giving up on the schedule after a few days - the payoff comes from consistency.