Ask a room of students how they revise and most will describe the same routine: reread the notes, highlight the important parts, reread the highlights. In one survey of university students, 84% said they reread their notes or textbook, and more than half said it was their number one strategy. Only 11% mentioned testing themselves, and just 1% ranked it first (Karpicke, Butler & Roediger, 2009).
That is a problem, because decades of research point the other way. The single most reliable way to make something stick is to practise pulling it out of memory, not putting it back in. This is called active recall, or retrieval practice. This guide explains what it is, why it works, how strong the evidence is, and exactly how to use it.
What active recall actually is
Active recall means trying to produce information from memory without looking at it. Closing the book and writing down what you remember is active recall. So is answering a practice question, explaining a process out loud, or drawing a diagram from memory.
The opposite is passive review: rereading, highlighting, watching the lecture again, or looking over a summary. Passive review puts information in front of your eyes. Active recall makes your brain go and find it.
Psychologists call the benefit of retrieval the testing effect. The word "testing" is misleading, though. It has nothing to do with grades. A quiz you set yourself on the bus counts. What matters is the act of retrieval.
The experiment that changed how we think about studying
In a well-known study, Henry Roediger and Jeffrey Karpicke gave students short science passages to learn under three conditions (Roediger & Karpicke, 2006):
Read it four times (study, study, study, study)
Read it three times, then recall it once (study, study, study, test)
Read it once, then recall it three times (study, test, test, test)
"Recall" simply meant writing down as much of the passage as they could remember, with no feedback. Students were then tested either five minutes later or a week later.
Five minutes after studying, rereading won: the read-four-times group recalled 83% of the passage. A week later the picture had flipped. The rereaders were down to 40%, while the students who had spent most of their time recalling kept 61%.
The most revealing detail is what students predicted. The rereaders were the most confident they would remember the material. Rereading makes a text feel familiar, and familiarity is easy to mistake for knowledge. Psychologists call this an illusion of competence.
Why retrieval works
Researchers still debate the precise mechanisms, but three explanations are well supported.
1. Retrieval strengthens the route back to the memory
Every time you successfully find a piece of information, you make it easier to find next time. Rereading strengthens your ability to recognise something. Retrieval strengthens your ability to recall it, which is what exams, conversations and real work demand.
2. Effort is part of the benefit
Retrieval that takes some struggle tends to produce more durable learning than retrieval that is effortless. The psychologist Robert Bjork calls these desirable difficulties: challenges that slow you down now but pay off later. A little forgetting before you practise is not a failure. It is what makes the practice work.
3. It shows you what you don't know
When you reread, everything looks familiar. When you try to recall, gaps become obvious. That feedback lets you spend your time on the parts you actually need, instead of polishing what you already know.
How strong is the evidence?
Unusually strong, for education research. The testing effect has been replicated across hundreds of studies, with learners from primary school to medical school, and with materials from vocabulary to maths to complex science texts.
A major review of ten popular study techniques rated practice testing as one of only two with high utility. The other was spacing out your study. Highlighting and rereading were rated low (Dunlosky et al., 2013).
Two large meta-analyses found that practice tests reliably beat restudying the same material (Rowland, 2014; Adesope, Trevisan & Sundararajan, 2017).
A systematic review of studies run in real schools and classrooms, not labs, found benefits in the large majority of cases (Agarwal, Nunes & Blunt, 2021).
Retrieval even beat concept mapping, a technique designed to build deep understanding, on a test a week later. That held for questions that required making inferences, not just recalling facts (Karpicke & Blunt, 2011).
Retrieval practice is not magic. It works best when you can recall at least some of the material, and when you check your answers afterwards. But as general advice to "test yourself more and reread less", it is about as safe as learning science gets.
Seven ways to practise active recall
You don't need special apps or equipment. Pick the methods that suit your subject.
1. The blank page
After a lecture or a chapter, close everything. On a blank page, write down all you can remember: key ideas, definitions, examples, how things connect. Then open your notes and compare, and mark what you missed or got wrong in a different colour. Those marks are your to-do list for the next session.
It feels uncomfortable the first time, because you will remember less than you hoped. That discomfort is the point.
2. Turn your notes into questions
Rewrite headings as questions. Causes of the First World War becomes What were the four main long-term causes of the First World War? Osmosis becomes What is osmosis, and how does it differ from diffusion?
Now your notes double as a quiz. Cover the answers and work through the questions out loud or on paper. The Cornell note-taking method builds this in from the start.
3. Flashcards, done properly
Flashcards are recall in its most portable form, but they are easy to misuse. A few rules make a big difference:
One idea per card. "What are the three stages of mitosis and what happens in each?" is really several cards.
Answer before you flip. Say or write the answer in full. "Yeah, I knew that" doesn't count.
Don't drop a card after one correct answer. Recalling something correctly once is a start, not the finish line. In one set of experiments, recalling each item correctly about three times in a session, then relearning it in later sessions, produced strong long-term retention at a manageable time cost (Rawson & Dunlosky, 2011).
Write your own. Making the cards is itself useful processing, and you will phrase things in a way that makes sense to you.
4. Practice questions and past papers
Past papers are retrieval practice that also trains you in the format, timing and wording of the real exam. Do them under realistic conditions, mark them honestly with the mark scheme, and treat every lost mark as a lesson: what did you not know, and what did you know but fail to show?
5. Explain it to someone (or something)
Explain a topic out loud as if teaching a friend who has missed the lesson. No notes. Wherever you hesitate, hand-wave or say "it just kind of happens", you have found a gap. No friend available? Explain it to a rubber duck, a pet or an empty chair. It works surprisingly well.
6. Draw it from memory
For processes, structures and relationships, draw instead of writing: the water cycle, a labelled heart, a timeline, a flowchart of a legal process, a free-body diagram. Then compare with the correct version. Diagrams force you to recall how the parts connect, not just what they are called.
7. Mix your questions up
Once you have a bank of questions, don't always quiz yourself in the same order or on one topic at a time. Mixing topics makes each question harder, because you first have to work out what kind of problem it is. That also happens to be what exams require.
A 20-minute recall session you can use today
If you are not sure where to start, use this template for any topic you studied in the past few days.
Time | What to do |
|---|---|
0–2 min | Choose one topic. Write its name at the top of a blank page. Put your notes out of reach. |
2–10 min | Blank-page recall: write or sketch everything you can remember. Keep going after the first rush of ideas. |
10–14 min | Check against your notes. Mark missing or wrong points in a second colour. |
14–18 min | Close the notes again and re-attempt only the parts you marked. |
18–20 min | Write three questions about the weakest parts to start your next session. |
Repeat the session two or three days later, then again the following week. Those growing gaps are where active recall meets spaced repetition, the second part of this series.
Common mistakes
Peeking too early
Looking at the answer after two seconds turns recall back into rereading. Give yourself a real attempt, even 20 or 30 seconds of effort, before you check.
Only using recognition
Multiple-choice quizzes are better than nothing, but producing an answer from scratch demands more than picking it from a list. Use free recall and short-answer questions for most of your practice.
Saving it for the week before the exam
Recall practice works best spread over weeks. A single burst of self-testing the night before is still better than rereading, but you lose most of the long-term benefit.
Mistaking struggle for failure
Recall practice will often feel worse than rereading, even while it works better. Judge your methods by what you remember a week later, not by how they feel in the moment.
Watch: active recall in practice
In this video, the doctor and YouTuber Ali Abdaal explains how he used active recall and spaced repetition to revise at medical school, with practical examples of each.
Frequently asked questions
Is active recall the same as spaced repetition?
No, but they work best together. Active recall is how you review: by retrieving from memory. Spaced repetition is when you review: at increasing intervals. Flashcard apps such as Anki combine both.
Does active recall work for understanding, or only for facts?
Both. Retrieval practice has been shown to help with inference questions and applying ideas to new problems, not just memorising definitions (Karpicke & Blunt, 2011; Agarwal, Nunes & Blunt, 2021). For conceptual subjects, focus on explaining, drawing and solving problems rather than recalling isolated facts.
What if I can't remember anything at all?
Then you need a little more initial learning first. Read the section once carefully, then try recalling it. Retrieval works best when there is something to retrieve. Aim for questions you get right roughly half to three-quarters of the time.
How long should a recall session be?
Short and frequent beats long and rare. Twenty to thirty focused minutes on one topic, repeated across several days, is more effective than a three-hour session once.
References
Adesope, O. O., Trevisan, D. A., & Sundararajan, N. (2017). Rethinking the use of tests: A meta-analysis of practice testing. Review of Educational Research, 87(3), 659–701. doi.org/10.3102/0034654316689306
Agarwal, P. K., Nunes, L. D., & Blunt, J. R. (2021). Retrieval practice consistently benefits student learning: A systematic review of applied research in schools and classrooms. Educational Psychology Review, 33(4), 1409–1453. doi.org/10.1007/s10648-021-09595-9
Dunlosky, J., Rawson, K. A., Marsh, E. J., Nathan, M. J., & Willingham, D. T. (2013). Improving students’ learning with effective learning techniques. Psychological Science in the Public Interest, 14(1), 4–58. doi.org/10.1177/1529100612453266
Karpicke, J. D., & Blunt, J. R. (2011). Retrieval practice produces more learning than elaborative studying with concept mapping. Science, 331(6018), 772–775. doi.org/10.1126/science.1199327
Karpicke, J. D., Butler, A. C., & Roediger, H. L. (2009). Metacognitive strategies in student learning: Do students practise retrieval when they study on their own? Memory, 17(4), 471–479. doi.org/10.1080/09658210802647009
Rawson, K. A., & Dunlosky, J. (2011). Optimizing schedules of retrieval practice for durable and efficient learning: How much is enough? Journal of Experimental Psychology: General, 140(3), 283–302. doi.org/10.1037/a0023956
Roediger, H. L., & Karpicke, J. D. (2006). Test-enhanced learning: Taking memory tests improves long-term retention. Psychological Science, 17(3), 249–255. doi.org/10.1111/j.1467-9280.2006.01693.x
Rowland, C. A. (2014). The effect of testing versus restudy on retention: A meta-analytic review of the testing effect. Psychological Bulletin, 140(6), 1432–1463. doi.org/10.1037/a0037559
Soderstrom, N. C., & Bjork, R. A. (2015). Learning versus performance: An integrative review. Perspectives on Psychological Science, 10(2), 176–199. doi.org/10.1177/1745691615569000
Discussion