Spacing beats cramming: the classic review of 317 experiments
In short: Across 839 assessments in 317 experiments, spreading study over separate sessions beat doing it all at once, and in only 12 of 271 direct comparisons did spacing show no benefit or a cost. The best gap between sessions grows with how long you need to remember the material.
| Paper | Distributed practice in verbal recall tasks: A review and quantitative synthesis |
| Authors | Nicholas J. Cepeda, Harold Pashler, Edward Vul, John T. Wixted, Doug Rohrer |
| Published | 2006 · Psychological Bulletin 132(3), 354–380 |
| Study type | Review and meta-analysis (landmark classic) · Peer-reviewed |
| What we read | Full text read. We read the authors' manuscript version on eScholarship. |
| Summarized |
What they did
The authors pooled 839 assessments of distributed practice from 317 experiments in 184 articles on verbal memory tasks (such as word lists and paired associates). They analysed both spacing (one sitting versus separate sessions) and lag (how far apart the sessions are) against the retention interval, the time until the final test.
Who took part
Participants in 317 experiments, mostly lab studies of verbal recall.
What they found
- Spaced presentations led to markedly better final-test performance than massed ones.
- Only 12 of 271 massed-versus-spaced comparisons showed no effect or a negative effect of spacing.
- The gap between study sessions that gave the best retention increased as the retention interval increased.
- There was not enough evidence to say whether expanding gaps (short, then longer) beat equal gaps.
Effect size: Reported as differences in percent recalled for each combination of gap and retention interval; there is no single headline effect size.
Limitations
- Mostly lab studies of verbal memory (word lists, facts), not complex skills or classrooms.
- Older studies with varied methods.
- Gives direction, not an exact schedule; later work refined the best gaps.
What this means for learners and parents
- Two 20-minute sessions on different days beat one 40-minute session.
- The further away the exam, the further apart your review sessions can be.
- Start early enough to have several separate sessions before a test.
Put it into practice (free tools)
- Get a spaced revision plan from your exam date
- Flashcards with spaced review
- 7 short days instead of one long one
Citation
Nicholas J. Cepeda, Harold Pashler, Edward Vul, John T. Wixted, Doug Rohrer (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin 132(3), 354–380. https://doi.org/10.1037/0033-2909.132.3.354