Space retrieval attempts at expanding intervals

Test yourself on material at 1 day, 3 days, and 1 week — not all in the same session.

Why it works

Each successful retrieval slows the forgetting curve — but only if the retrieval is effortful. Retrieval attempted too soon (before any forgetting has occurred) requires little effort and produces minimal strengthening. Retrieval attempted just before complete forgetting — the sweet spot — produces the largest memory gain per unit of study time, and successive retrievals at expanding intervals push retention further than massed retrieval in a single session.

How to do it

1. After an initial study session, schedule your first retrieval test for 24 hours later — not the same day.
2. If you succeed at 24 hours, schedule the next test for 3–5 days after that.
3. If you fail, schedule the next test for only 1–2 days — shorter interval for weaker memories.
4. Continue expanding the interval for material you can reliably retrieve, until the interval matches how long you need to retain it.

Evidence

The combination of retrieval practice and spaced intervals (spaced retrieval) produces better long-term retention than either alone. Cepeda et al. (2006) quantified optimal study-to-test gaps across a range of retention intervals in a large-scale meta-analysis. (rct)

Optimal intervals depend on the desired retention horizon and initial learning strength; the intervals above are practical starting points rather than precisely calibrated prescriptions.

Sources

• Cepeda et al. (2006), distributed practice in verbal recall tasks: a review and quantitative synthesis, Psychological Bulletin
• Karpicke & Roediger (2008), the critical importance of retrieval for learning, Science

Common mistake

Doing all retrieval attempts in one session ("I quizzed myself 20 times tonight") — massed retrieval produces good immediate performance but poor week-later retention compared to the same attempts spread across days.