Study Less, Remember More: Retrieval Practice and Spaced Repetition Explained

What the research says

In 2013, a team of psychologists led by John Dunlosky published a large review in the journal Psychological Science in the Public Interest. They looked at ten common study techniques and rated each one by how well the evidence supported it across different ages, subjects and situations.

Only two techniques earned their highest rating: practice testing and distributed practice. Three more, including interleaving and explaining ideas to yourself, were rated moderate. And five, including rereading, highlighting and summarising, were rated low utility.

That last group is uncomfortable reading, because it describes how many of us studied for years.

Technique 1: Retrieval practice (testing yourself)

Retrieval practice means pulling information out of your memory rather than putting it back in. Instead of rereading your notes on photosynthesis, you close them and try to write down everything you remember, then check what you missed.

Why it works

Every time you successfully recall something, you strengthen the memory and make it easier to find next time. Rereading feels familiar and comfortable, which tricks us into thinking we know the material. Testing reveals what we actually know, and the act of recalling is itself what builds the memory.

One of the best-known studies, by Henry Roediger and Jeffrey Karpicke, compared students who reread a passage with students who were tested on it. A week later, the tested students remembered considerably more, even though the rereading group had felt more confident.

How to use it

• Blank page recall: close your notes, write everything you remember about a topic, then check and fill the gaps in a different colour.
• Flashcards, used properly: say or write the answer before you turn the card. If you just flip and nod, it's rereading in disguise.
• Past papers and practice questions: exam-style questions are retrieval practice in its most useful form, because they also train you for the real exam.
• Teach it: explain a topic out loud to a friend, a parent or an empty room, without notes.
• Make your own questions: after a lesson, write five questions you think a teacher might ask. Answer them a few days later.

The key point

Retrieval practice should feel a bit hard. If you can answer everything easily, the questions are too easy or you're testing too soon. That feeling of effort is a sign the technique is working, not a sign you're failing.

Technique 2: Spaced repetition (distributed practice)

Spaced repetition means spreading your study of a topic over several sessions with gaps between them, instead of cramming it all at once.

Why it works

Memories fade over time, but each time you revisit information just as it starts to fade, the memory comes back stronger and lasts longer. Cramming can get you through a test tomorrow, but much of it is gone a week later. Spacing makes learning stick.

How to use it

A simple pattern works for most students:

• Learn something today.
• Review it the next day.
• Review it again about three days later.
• Then a week later.
• Then two to three weeks later.

Each review should be retrieval practice, not rereading: test yourself on it, then check.

Flashcard apps that use spaced repetition do this scheduling for you, showing cards you struggle with more often and easy ones less often. A paper version works too: sort cards into boxes for "every day", "every three days" and "every week", and move cards between boxes as they get easier or harder.

Planning with spacing

Spacing changes how you plan revision. Instead of studying one topic for a whole week and moving on, rotate through several topics, coming back to each one regularly. A revision timetable with topics repeating every few days is far more effective than one where each topic appears once.

Putting them together

The two techniques work best combined: test yourself, spaced out over time. Here's what a week of revision might look like for one subject:

• Monday: learn a new topic in class or from notes. In the evening, do a blank-page recall of it for ten minutes.
• Tuesday: answer five practice questions on Monday's topic.
• Thursday: flashcards on Monday's topic, plus last week's topic.
• Saturday: a short past-paper question that mixes several topics.
• The following week: Monday's topic comes back once more, in a mixed quiz.

None of these sessions is long. Fifteen to thirty minutes of focused retrieval usually beats two hours of rereading.

A third technique worth knowing: interleaving

Interleaving, rated "moderate" in the Dunlosky review, means mixing different types of problems in one practice session instead of doing twenty of the same kind in a row. In maths, for example, mix questions on fractions, percentages and ratios rather than doing a page of each.

It feels harder and messier, because you have to work out which method each question needs. That's exactly the skill exams test. It works especially well in maths, physics and other subjects where choosing the right method is half the challenge.

Why we keep using the techniques that don't work

If rereading and highlighting are so much less effective, why do so many students rely on them?

Because they feel good. Rereading makes material feel familiar, and familiarity feels like knowledge. Highlighting feels active. Testing yourself, on the other hand, is uncomfortable: you find out what you don't know. Psychologists sometimes call this kind of productive struggle a "desirable difficulty". It's harder in the moment and better in the long run.

Knowing this helps. When revision feels effortful and slightly frustrating, that's often a sign you're doing it right.

A four-week plan before an exam

If an exam is a month away, here's a simple way to use both techniques:

• Week 1: list every topic on the syllabus. Rate each one red, amber or green for how confident you feel. Make flashcards or question lists for the red and amber topics.
• Week 2: study two or three topics a day with blank-page recall and practice questions. Start reviewing week 1's cards on a spaced schedule.
• Week 3: begin timed past-paper questions, mixing topics. Every mistake goes on a new flashcard.
• Week 4: full past papers under exam conditions, plus quick daily flashcard reviews. Re-rate your topics; the reds should now be ambers or greens.

The night before, do a light review and sleep. Sleep is when memories consolidate, and an all-night cram undoes much of the work.

Common questions

"Is it bad to reread at all?" No. Reading your notes once to understand a topic is fine. The problem is relying on rereading as your main way to revise.

"How many flashcards should I make?" Fewer than you think. Focus on key facts, definitions and formulas. A small deck reviewed properly beats a huge one you never finish.

"Does this work for every subject?" It works for nearly everything that involves remembering and applying knowledge: sciences, languages, history, maths methods, vocabulary. For skills like essay writing, combine it with plenty of practice writing and feedback.

Tips for parents

You don't need to be an expert in your child's subjects to help:

• Ask questions instead of checking notes. "Tell me three things you learned about volcanoes" is retrieval practice.
• Encourage little and often. Twenty minutes a day across the week beats three hours on Sunday.
• Celebrate effort when it's hard. Remind them that struggling to remember is part of learning.
• Help them plan spaced revision with a simple calendar.

The bottom line

The most effective way to study isn't complicated or expensive. Test yourself instead of rereading, and spread your practice out over time instead of cramming. It feels harder, and it works much better.

Past papers are one of the best tools for both, and we've written a practical guide to revising with past papers. You'll also find free worksheets and papers on our study materials page.

Frequently asked questions