Understanding instead of memorising: spaced repetition and retrieval practice

Imagine reading through your notes for the third time the night before an exam. The pages feel familiar now, you can almost predict the sentences, and a feeling of “I know this” builds up. The next day, looking at the exam paper, you realise that some of that familiar information isn’t there. Almost everyone has had this experience, and it is no accident. Research in cognitive psychology shows that there is often a gulf between the feeling of learning and actual learning. In this article we look at the two best-supported methods for closing that gulf: retrieval practice and spaced repetition. The article is written for parents and teachers as much as for students.

Familiarity is a trap

Reading a text again and again makes it easier to recognise. But in exams, and in life, we usually need to recall information and use it, not just recognise it. Recognition and recall are different processes. You can spot a friend’s face in a crowd straight away, but you struggle when asked to draw the same face on paper.

Researchers call this the illusion of fluency: because information is easy to process, we assume we have learned it well. This is one reason why methods such as rereading and highlighting with coloured pens are so widespread. They are easy and they feel good. However, a comprehensive review published in 2013 by John Dunlosky and colleagues evaluated ten common learning techniques in the light of hundreds of studies, and rated rereading and highlighting as low utility techniques. The two techniques placed at the highest level of utility in the same review were practice testing and distributed practice.

This does not mean rereading is completely useless. But it does show that if you use the same time differently, much more lasting results are possible.

Retrieval practice: testing teaches

Most of us think of tests only as a measuring tool: learning happens somewhere, and the test measures how much we have learned. Yet research shows that trying to pull information out of memory is itself a powerful learning activity. This finding is called the testing effect, and the way of studying that relies on deliberately recalling information from memory is called retrieval practice.

A classic experiment

In a frequently cited study published in 2006 by Henry Roediger and Jeffrey Karpicke, university students studied short science texts. One group read the text repeatedly; the other read the text, then closed the book and tried to write down what they remembered. On a test a few minutes later, the rereading group did slightly better. But on tests a few days and a week later, the picture reversed: the group that had tried to recall had retained noticeably more.

Perhaps the most thought-provoking part of this study was the students’ own predictions. The students who reread tended to think they would remember more. In other words, our intuition about which method works can contradict the actual result.

Why does it work?

Recalling information from memory strengthens the route to it. Each successful recall makes the next one easier. Also, when you test yourself, you see clearly what you know and what you don’t; this directs your study to the places that really need it. The idea Robert Bjork called desirable difficulties is related: struggling a little while studying may seem to slow learning down, but in the long run it can make it last longer.

Spaced repetition: spreading it out over time

The second powerful finding is the spacing effect. When the same total study time is spread out over time instead of being squeezed into a single session, information stays in memory much longer. This effect was first observed in the late 19th century in memory experiments the German psychologist Hermann Ebbinghaus carried out on himself, and it has since been replicated in countless studies, across different age groups and different subjects. A large review published in 2006 by Nicholas Cepeda and colleagues, which brought together hundreds of experiments, showed that spaced study consistently gives better results than massed study.

Ebbinghaus’s observation known as the forgetting curve shows that newly learned information is forgotten quickly, especially in the first days, and then forgetting slows down. Spaced repetition is a strategic move against this curve: when you recall information just as you are about to forget it, the recall takes a little effort and the information becomes more resistant to the next round of forgetting.

How long should the gap be?

The general principle from the research is this: the longer you want to remember something, the longer the gaps between reviews can be. For an exam next week, spreading reviews over a few days may be enough, while for a topic you want to remember a year from now, the gaps can stretch to weeks and months. There is no single magic interval; but “leaving everything to the last night” is the worst option in almost every situation.

A practical approach is to use expanding intervals: after learning a new topic, test yourself the next day, a few days later, a week later and a few weeks later. Shorten the gap for things you struggle to recall, and lengthen it for things you recall easily.

Memorising or understanding?

Let’s correct an important misunderstanding here. The words “retrieval” and “repetition” can sound like rote learning. But these methods are not limited to remembering definitions and formulas.

Retrieval can be done with questions like “Why is this formula the way it is?”, “Can I explain this with another example?” and “How does this idea relate to the one I learned last week?” just as much as “What is this formula?”. In a study published in 2011 by Karpicke and Blunt, students who did retrieval practice outperformed students who studied by making concept maps, not only in remembering information from the text but also on questions that required inference.

So the right question is not “memorising or understanding?” but “am I reinforcing what I understand by recalling it from memory, or am I just rereading?”. When you truly understand an idea, it becomes easier to remember; when you recall it regularly, you begin to understand it more deeply. The two are not rivals but partners.

Mixing it up

Interleaved practice, rated as moderately useful in the review by Dunlosky and colleagues, is also worth mentioning here. In maths, mixing different types of problem instead of solving ten of the same type in a row makes the student ask, for each problem, “Which method does this need?”. That is exactly the skill we need in exams and in real life.

Common mistakes when using these methods

Even a good method may not give the expected result if it is applied badly. Here are a few traps students often fall into:

• Looking at the answer straight away: When testing yourself, revealing the answer after a few seconds of struggle removes the main benefit of retrieval. First really try to remember, then check.
• Skipping feedback: Testing yourself and never checking the right answer can reinforce wrong information. After each attempt, compare your answer with the source.
• Picking only easy questions: Answering questions you already know over and over feels good, but the real gain is in the questions you struggle with.
• Closing the gap too early: Recalling something correctly once does not mean you have learned it for good. Try again a few days later.
• Squeezing reviews into the days before the exam: The benefit of spaced repetition comes from reviews being genuinely spread out over time. Five reviews crammed into the last two days do not have the same effect.

A simple but effective way to avoid these mistakes is to make a short plan before you start studying and to mark review days on a calendar.

Putting it into practice: a sample one-week plan

Say a student learned about photosynthesis on Monday. A simple plan that combines spaced repetition and retrieval might look like this:

1. Monday (first learning): Study the topic carefully. When you finish, close the book and write down everything you remember on a blank sheet, or draw a diagram. Then compare with the book and mark what you missed.
2. Tuesday (1 day later): Without looking at the book, ask yourself three questions: “What does photosynthesis need? What does it produce? Why does it matter to the plant?” After answering, check.
3. Thursday (3 days later): Try explaining the topic to a friend or family member. The points where you get stuck are the places you need to look at again.
4. The following Monday (1 week later): Solve a few practice questions on the topic, mixed in with questions from other topics.
5. A few weeks later: Do a short general review test.

The total time for this plan is not much more than one long session. The difference lies in how the time is spread out, and in doing each review by “recalling” rather than “reading”.

Studying with cards

Flashcards are the classic way to combine retrieval and spaced repetition. A question goes on one side of the card and the answer on the other. In the system proposed by Sebastian Leitner in the 1970s, cards are sorted into several boxes: a card you get right moves to the next box, which is reviewed less often; a card you get wrong goes back to the first box. This way, things you struggle with come up more often and things you know well come up less often. Writing not only definitions but also “why” and “how” questions on the cards moves the method from memorising to understanding.

Notes for teachers and parents

• Low-stakes tests: Short in-class questions that don’t cause anxiety about marks, and recall activities at the start of a lesson, are an easy way to benefit from the testing effect. The aim is not to give marks but to prompt recall.
• Going back to earlier topics: Asking a few questions on old topics in new units builds spaced repetition into the curriculum naturally.
• Normalising mistakes: Not being able to recall something during retrieval is not failure; it is part of the process. Seeing the right answer after a mistake strengthens learning.
• Offering an alternative to last-night cramming: Planning short review sessions with your child spread over the two weeks before an exam is often more productive than a long session on the last night.

These principles are also at the heart of Kuazara’s design: when we say “Don’t memorise. Understand.”, we mean using information, questioning it and recalling it again over time, rather than rereading it. For more, have a look at our learning science articles and our topics page. In Kuazara’s interactive lessons you will find short retrieval questions at the end of every topic, so you can reinforce what you have learned by trying things out and recalling them.