Is spaced repetition worth it for test prep? What the evidence shows, and when it doesn't help
Yes, for anything you need to remember on test day: vocabulary, formulas, rules, question-type tricks. Spreading study out over time and testing yourself are the two techniques that a major review of learning research rated high utility, ahead of rereading and highlighting. It helps less for skills that come from doing, like speed under a timer, where timed practice matters more.
What spaced repetition is
Spaced repetition combines two ideas that have been studied separately for decades.
- Spacing: studying the same material in several sessions spread out over days, instead of in one block.
- Retrieval practice: recalling the answer from memory (a flashcard, a practice question) instead of reading it again.
A spaced repetition system schedules reviews so each item comes back just as you are about to forget it: soon after you first learn it, then at growing gaps.
The evidence for spacing
The largest review of spacing is Cepeda and colleagues (2006). They pooled 839 assessments of distributed practice from 317 experiments in 184 articles, all on verbal recall.
Their main finding is about timing, not just spacing. The best gap between study sessions depended on how long you need to remember for: the longer the time until the test, the longer the best gap. Cramming the night before can work for a test the next morning; it works poorly for anything you need in a month.
The evidence for testing yourself
Roediger and Karpicke (2006) had students read prose passages and then either reread them or take recall tests without feedback. Then everyone took a final test, either 5 minutes, 2 days or a week later.
| Final test | Who did better |
|---|---|
| After 5 minutes | Those who restudied |
| After 2 days | Those who were tested |
| After 1 week | Those who were tested |
The detail that matters most: rereading made students more confident they would remember, even though they remembered less later. Rereading feels productive because the material looks familiar. Testing feels harder and works better.
How the techniques compare
Dunlosky and colleagues (2013) reviewed ten common study techniques and rated how widely each one's benefits hold up across learners, materials and kinds of test.
| Rating | Techniques |
|---|---|
| High utility | Practice testing, distributed practice |
| Moderate utility | Elaborative interrogation, self-explanation, interleaved practice |
| Low utility | Summarisation, highlighting, the keyword mnemonic, imagery for text, rereading |
The two highest-rated techniques are exactly the two that spaced repetition combines. The authors specifically suggest practice testing in place of rereading.
Where it fits in test prep
Spaced repetition is best for things that have a right answer you either remember or don't:
- Vocabulary for the SAT, GRE or a verbal reasoning test.
- Formulas and facts: area and volume formulas, percentage shortcuts, squares and fractions as decimals.
- Rules of a question type: the five rules in a matrix puzzle, the meaning of "cannot say" in a verbal test.
- Your own mistakes: a question you got wrong, brought back a few days later.
It is weaker for speed and for reasoning on new problems. Recognising a number pattern quickly comes from seeing many patterns, and keeping pace under a 15-minute clock comes from timed runs. For those, plan timed practice, spread over days for the same spacing reason.
A sample week
For someone with a test in three weeks and 30 minutes a day:
- 10 minutes of reviews from a spaced repetition deck: words, formulas and past mistakes that are due today.
- 15 minutes of new practice on one question type, with explanations.
- 5 minutes adding today's mistakes to the deck.
- Once or twice a week, a full timed test instead of the above.
preplaud's practice works this way: questions you get wrong come back for review on later days. Our number memory guide explains why memory is limited and how chunking gets around it, and the guide on what practice can and can't do covers the evidence on practice in general.
Our view, and the limits
Our opinion: the single change worth making for most people is to stop rereading notes and start answering questions from memory. Doing it on a schedule matters as much: what you got wrong should come back a few days later, and again after that. That is how review works in preplaud: your mistakes return on later days, with the explanation, so each session works on what you are most likely to forget.
The limitations: Cepeda's review covers verbal recall, and Roediger and Karpicke used prose passages; both are closer to vocabulary than to solving a new maths problem. Dunlosky and colleagues rated interleaved practice, which mixes problem types, as promising but with limited evidence at the time. And none of these studies were on aptitude tests used for hiring, where speed and unfamiliar problems matter most.
Questions people ask
Is spaced repetition better than cramming?
For a test more than a day or two away, yes. Cepeda and colleagues found the best gap between sessions grows with the time until the test, so one long session the night before suits only a test the next day.
How long should the gaps between reviews be?
Longer the further away your test is. Spaced repetition apps grow the gaps for you as you keep getting an item right.
Does spaced repetition work for maths?
It works for the facts and formulas maths needs. For solving new problems, timed practice on mixed question types matters more.
Why does rereading feel like it works?
Familiar text feels known. In Roediger and Karpicke's study, rereading raised students' confidence while giving worse recall after two days and a week.
Practise for it
preplaud has timed practice with worked explanations for the aptitude tests employers use, the SAT, GRE and GMAT, and quant interviews. Start free, with no account needed; Premium opens every level and the full mock tests, with a 7-day free trial.
Sources
- Cepeda et al. (2006), Distributed practice in verbal recall tasks: a review and quantitative synthesis, Psychological Bulletin
- Roediger and Karpicke (2006), Test-enhanced learning: taking memory tests improves long-term retention, Psychological Science
- Dunlosky et al. (2013), Improving students' learning with effective learning techniques, Psychological Science in the Public Interest