Cramming vs spaced repetition: what actually works

What cramming is, and why everyone does it

Cramming means studying a lot of material in one long block, or a few blocks close together, just before a test. Psychologists call it massed practice. Its opposite is distributed or spaced practice: the same study, split into sessions with gaps between them.

Almost every student crams at some point. Deadlines pile up, the exam suddenly feels real, and a long session feels like the responsible thing to do. And it does work, a little: if the test is tomorrow morning, some of what you crammed tonight will still be there. The question is what you're paying for that, and what happens afterwards.

Why cramming feels like it works

After a few hours with the same pages, everything looks familiar. That familiarity feels like knowing, but it's mostly fluency: the material is easy to read because you've just read it. Recognising a page isn't the same as recalling its content under exam conditions, and it says little about next month.

Our sense of what's working is a poor guide here. In a 2009 study, Nate Kornell had students learn word pairs with flashcards, either in one large stack (each card comes back after a long gap) or in four small stacks studied one after another (each card comes back quickly). Across three experiments, spacing beat massing for 90% of the participants. Yet after the first session, 72% of them believed massing had worked better.

What happens after the exam

In the 1880s Hermann Ebbinghaus measured how quickly he forgot lists he had learned. After a day, he had lost about two thirds of the original learning effort; after a month, about four fifths. The curve is steep at first and then flattens, and material studied once, however intensely, sits on the steep part. More in the forgetting curve, explained.

For a one-off quiz, that may not matter. For courses that build on earlier topics, and for finals and licensing exams that cover a whole year, it matters a lot: crammed material has to be learned again, almost from the start, every time it's needed.

What the research says

Hundreds of experiments, one direction

The spacing effect is one of the most replicated findings in psychology. A 2006 review by Nicholas Cepeda and colleagues gathered more than 400 reports on spaced versus massed study of verbal material, and spaced study came out ahead across them. A 2013 review of study techniques led by John Dunlosky rated distributed practice as one of only two techniques with high utility for students, beside practice testing.

Flashcards in particular

Kornell's study above is the most direct test for flashcard users. One large stack beat four small ones, and it also beat cramming, meaning massed study on the last day before the test. If you study with paper cards, keeping them in one big shuffled stack is spacing for free.

Over years, not just weeks

In a nine-year study, Harry Bahrick and three members of his family learned and relearned 300 foreign-language word pairs in either 13 or 26 sessions, 14, 28 or 56 days apart, and were tested up to five years after training ended. The longer gaps slowed learning slightly at first, but retention was substantially higher: 13 sessions 56 days apart kept about as many words as 26 sessions 14 days apart. Half the sessions, the same result, simply by spacing them further.

How far apart should study sessions be?

In 2008, Cepeda's team taught more than 1,350 people a set of facts, gave them one review after a gap of up to three and a half months, and tested them up to a year later. The best gap depended on when the test was:

Compared with reviewing on the same day, the best gap improved recall on the final test by 64% on average. Two practical rules follow: a gap that's too short wastes most of the benefit, and the further away the test, the longer the gaps can be. Spaced repetition apps apply the same idea card by card, with gaps that grow each time you remember. See FSRS explained and our spaced repetition guide.

Cramming and spacing, side by side

Why spacing works

When you come back to a fact after a gap, recalling it takes effort, because the memory has started to fade. That effortful recall is exactly what strengthens it: the next drop is gentler, so the next gap can be longer. Massed study skips the effort, since the answer is still fresh, and so builds little lasting strength. Robert Bjork calls this kind of useful effort a desirable difficulty.

FSRS, the algorithm FlashCardz uses, puts a number on it: each card has a stability, the days until your chance of recalling it falls to 90%. A successful recall after a gap raises stability far more than one right after the last review. That's why a card you know can wait months between reviews, and why ten spread-out reviews keep a fact for over a year.

Cramming and sleep

Cramming often eats into sleep, which makes it worse twice over. Sleep after learning helps stabilise what you studied that day, as Susanne Diekelmann and Jan Born describe in their 2010 review. And sleep before learning matters too: in a 2007 study by Seung-Schik Yoo, Matthew Walker and colleagues, people kept awake for a night showed less activity in the hippocampus while learning new material and remembered markedly less of it later.

An all-nighter before an exam gives up the night that would have consolidated the last day's study, and walks into the exam on a brain that's worse at both learning and recalling. A short review and a full night's sleep beats it.

If the exam is next week

You can still space. Gaps of hours and a day are better than none.

1. Today: list the topics past exams ask most, and make flashcards for those first. Leave the rare topics for last.
2. Every day: two or three short sessions (morning, afternoon, evening) on the same cards, instead of one long one.
3. Test, don't reread: answer each card before you turn it, and put the ones you miss back in the pile.
4. From day three: add timed past questions, and turn each miss into a card.
5. The day before: only your weakest cards, then stop early.
6. The night before: sleep. The morning of: a ten-minute run through key facts.

If the exam is a month or more away

Start spacing now and most of the work is done before the last week. Make cards for each lecture within a day or two, review the due cards every day, and add past questions as the exam approaches. Our four-week exam plan lays it out week by week, and how many flashcards a day shows what each pace costs in daily reviews.

Successive relearning: cramming done right

There's a way to keep what cramming does well, practising until you get things right, without its cost. Katherine Rawson, John Dunlosky and Sharon Sciartelli call it successive relearning: practise each concept until you recall it correctly, then come back in later sessions and relearn it to the same standard. In their 2013 study with university students, it improved performance on course exams and long-term retention.

Spaced repetition is successive relearning with a schedule: each session brings back the cards you're about to forget, and a card you miss stays in the session until you get it.

Do both, in the right order

Cramming on top of spaced review is fine; cramming instead of it is the problem. Start spacing early, so the last days are a focused push on weak spots rather than a first meeting with the material.

FlashCardz is built for that order. Give a course its exam date and no card is scheduled for after the day before the exam, so everything has been reviewed in time. The course with the nearest exam comes first, and you can study extra cards whenever you want. After the exam, the normal schedule returns, so what you learned stays for the next course. See how it works.