Use expanding review intervals
Review soon after first learning, then at progressively longer gaps as memory strengthens.
Key takeaways
- What it is: Review soon after first learning, then at progressively longer gaps as memory strengthens.
- Why it works: A memory you can just barely retrieve gains the most from being retrieved. Expanding the gap keeps each review near that edge of difficulty: early reviews catch the fast initial forgetting, and later, wider gaps match the slower decay of a now-stronger trace.
- Evidence: Backed by randomized trials / meta-analyses.
- Avoid: Reviewing on a flat, frequent schedule forever, which wastes effort on items already well known and starves the ones near forgetting.
Why it works
A memory you can just barely retrieve gains the most from being retrieved. Expanding the gap keeps each review near that edge of difficulty: early reviews catch the fast initial forgetting, and later, wider gaps match the slower decay of a now-stronger trace.
How to do it
- 1Schedule the first review within a day of learning, while the trace is still fragile.
- 2Lengthen each subsequent interval (days, then weeks, then months) as recall succeeds.
- 3Shorten the interval again whenever a review fails — let difficulty steer the schedule.
What the evidence says
RCT / meta-analysisExpanding-interval schedules reliably outperform massed review for long-term retention. Whether expanding beats a fixed equal spacing is more mixed, but both beat cramming.
Honest caveat: The exact expanding schedule matters less than that gaps exist and grow roughly with mastery; do not over-tune the numbers.
Common mistake
Reviewing on a flat, frequent schedule forever, which wastes effort on items already well known and starves the ones near forgetting.
IX Coach tracks how solidly you hold each item and stretches or contracts the next review interval to match, instead of using one fixed cadence.
Practice this with IX Coach →