Spacing or massing, what the meta-analysis says
Massing means studying an idea several times in a row in the same session. Spacing means letting time pass between sessions. Cepeda and colleagues gathered 839 measures, taken from 317 experiments and 184 articles. Their conclusion is clear, spacing beats massing. They also note that the best gap between two sessions grows when the test is further away (Cepeda et al., 2006).
This idea holds a good place in Dunlosky and colleagues’ review of ten techniques. Distributing your study and practice testing are the two techniques rated high utility, while summarizing, highlighting and rereading are rated low utility (Dunlosky et al., 2013). A synthesis by Kang points the same way, spacing can be used in real classes, not only in a lab (Kang, 2016). For you, this means one thing. Several small sessions spread out beat one big one the week of your finals.
The best gap depends on how far away the exam is
Cepeda and colleagues’ 2008 study is the most precise on this point. More than 1,350 people did two sessions separated by a gap of up to 3.5 months, then a final test up to a year later (Cepeda et al., 2008). The result reads as a share of the time before the test.
If the test is in a week, the best gap is about 20 to 40% of that time. If it is in a year, it falls to about 5 to 10% (Cepeda et al., 2008). The further away the exam, the smaller the relative gap, even though the gap in days gets longer. Example with an exam in 10 days, you go back over the idea 2 to 4 days after the first session. You do not need to be exact to the day. These are benchmarks, not rules.
Why we get it wrong about what works
Spacing feels less effective in the moment, and that is the trap. Kornell had people learn GRE-style vocabulary with flashcards, either in one big spaced deck or in four small massed decks. Spacing was more effective for 90% of the participants. Yet after the first session, 72% thought massing worked better (Kornell, 2009).
The reason is simple. When you go back to an idea quickly, it comes back without effort, and that ease looks like learning. When you go back later, you have to dig for it, and it feels harder. Bjork and colleagues call this desirable difficulties, an effort that gets in the way now but helps later (Bjork et al., 2013). If a spaced review feels less smooth than rereading the night before, that is not a sign that it works less well. It is more likely the opposite.
How to space in practice
Rawson and Dunlosky followed 533 students across three experiments, with more than 100,000 responses scored by hand. Their advice is specific. Recall an idea correctly 3 times in the first session, then relearn it 3 times at widely spaced intervals, which they call successive relearning (Rawson and Dunlosky, 2011).
In practice, for a study sheet, you first quiz yourself without looking at the sheet, until you get every question right. You note what failed, you go back to it, then you put the sheet aside. A few days later you quiz yourself again. If you get stuck, you look at the answer and try again. Prepare your finals, AP exams or SAT this way, chapter by chapter. What matters is not a perfect calendar. It is never doing all your passes in the same evening.
| Exam in | Best gap between two sessions |
|---|---|
| One week | about 20 to 40% of the delay |
| One year | about 5 to 10% of the delay |
| 10 days (worked example) | go back 2 to 4 days after the first session |
Sources · Cepeda et al., 2008
Frequently asked questions
- How many days should I leave between two reviews?
- It depends on how far away the exam is. For an exam in 10 days, going back over the idea 2 to 4 days after the first session follows Cepeda’s benchmarks (Cepeda et al., 2008).
- Why does spacing feel less effective than cramming it all at once?
- Because ease in the moment looks like learning. In Kornell’s study, 72% thought massing worked better, yet spacing won for 90% of them (Kornell, 2009).
- How many times do I need to recall an idea to keep it?
- Rawson and Dunlosky advise 3 correct recalls in the first session, then 3 relearnings at widely spaced intervals (Rawson and Dunlosky, 2011).
Lumi forgets over time like a real brain, and he comes back to an idea at the right moment instead of handing it to you several times in a row. A star lights up in the sky of knowledge when an idea has been retained three times, on different days, and it fades when it needs another look. The night before an exam, the Mist rises over the sky, and each right answer pushes it back. Lumi puts spacing into practice.
Sources
- Cepeda, Vul, Rohrer, Wixted, Pashler (2008). Spacing effects in learning. A temporal ridgeline of optimal retention. Psychological Science, 19(11). doi.org/10.1111/j.1467-9280.2008.02209.x
- Cepeda, Pashler, Vul, Wixted, Rohrer (2006). Distributed practice in verbal recall tasks. A review and quantitative synthesis. Psychological Bulletin, 132(3). doi.org/10.1037/0033-2909.132.3.354
- Kornell (2009). Optimising learning using flashcards. Spacing is more effective than cramming. Applied Cognitive Psychology, 23(9). doi.org/10.1002/acp.1537
- Kang (2016). Spaced repetition promotes efficient and effective learning. Policy Insights from the Behavioral and Brain Sciences, 3(1). doi.org/10.1177/2372732215624708
- Rawson, Dunlosky (2011). Optimizing schedules of retrieval practice for durable and efficient learning. How much is enough?. Journal of Experimental Psychology. General, 140(3). doi.org/10.1037/a0023956
- Dunlosky, Rawson, Marsh, Nathan, Willingham (2013). Improving students' learning with effective learning techniques. Psychological Science in the Public Interest, 14(1). doi.org/10.1177/1529100612453266
- Bjork, Dunlosky, Kornell (2013). Self-regulated learning. Beliefs, techniques, and illusions. Annual Review of Psychology, 64. doi.org/10.1146/annurev-psych-113011-143823
