Active recall

What is active recall?

Active recall is bringing information back to mind without looking at it: you read a question, such as “What is the capital of Australia?”, and produce the answer before you check it. Psychologists usually call it retrieval practice; “active recall” is the name students and flashcard apps use.

The opposite is passive review: rereading notes, highlighting or watching a lecture again. There the information is in front of you, so you only need to recognise it. In active recall you have to rebuild it yourself.

Why does active recall work?

Active recall works because retrieving a memory changes it: what you have recalled is easier to recall later than what you have only reread. This is the testing effect, and two meta-analyses, which pool the results of many studies, found it to be reliable.^[1][2] For more depth, see retrieval practice and the testing effect.

In a well-known 2006 study, students read a short science passage, then either reread it or wrote down everything they remembered.^[3] Rereading did slightly better on a test 5 minutes later. A week later, the recall group remembered more: 56% of the passage's ideas against 42%.^[3]

Researchers do not yet agree on exactly why retrieval strengthens memory. The effort seems to matter: recalling an answer helped more than recognising it, as in multiple choice.^[1] A test also shows you what you do not know, while rereading hides it.

Is active recall better than rereading?

Yes: for remembering over days and weeks, active recall beats rereading and highlighting. A 2013 review of ten common study techniques rated practice testing as one of only two “high utility” techniques, along with distributed practice, and rated rereading, highlighting and summarising as “low utility”.^[5] In a 2011 study, recall also beat concept mapping, drawing a diagram of the ideas while reading, including on questions that required inferences.^[4]

Most students still reread. In a 2009 survey, 84% listed rereading as a study strategy and only 11% said they practised recall.^[6] Rereading feels more effective because familiar text is easy to mistake for knowledge, and students in these experiments expected recall to work less well than it did.^[3][4] But recognising an answer is not the same as producing it.

How is active recall different from spaced repetition?

Active recall is how you review, by answering from memory; spaced repetition is when you review, at intervals that grow over days, weeks and months. They are separate techniques, and they work best together.

Spaced repetition relies on the spacing effect: study spread over time is remembered longer than the same amount of study in one block.^[5] Flashcard apps such as Anki combine the two. Each review is a recall test, and an algorithm such as SM-2 or FSRS uses your answer to decide when the card comes back. For example intervals, see the spaced repetition schedule.

How do you practise active recall?

Hide the source, try to produce the answer, then check it. Four methods cover most needs:

• Flashcards. Say or write your answer before you turn the card. Cards that ask for one idea each are easier to answer and grade.
• Free recall. After a chapter or lecture, close your notes, write down everything you remember, then compare with the source. This is the method used in the studies above.^[3][4]
• Practice questions. Answer past exam papers, end-of-chapter questions or your own questions without looking at your notes.
• Explaining from memory. Explain a topic aloud or in writing as if teaching it, then check what you missed.

Prefer formats where you produce the answer over formats where you choose it: recall helped more than multiple choice, although multiple choice still helped.^[1]

What are common mistakes with active recall?

The most common mistakes turn active recall back into passive review, or stop it too early.

1. Turning the card too soon. If you look before making a real attempt, you recognise instead of recall. Commit to an answer, even when unsure.
2. Skipping the check. Testing helps even without feedback, but the benefit was larger in studies that showed learners the material again after the test.^[1]
3. Stopping after the first correct answer. In a 2008 study, students who kept being tested on word pairs they already knew recalled about 80% a week later; when those pairs were dropped from testing, they recalled about a third.^[7] This is why flashcard apps keep showing cards you know, at longer intervals.
4. Doing all the recall in one session. Spreading it over several days adds the spacing effect to the testing effect.^[5]
5. Trusting how easy studying feels. Students' predictions of how much they would remember were unrelated to how much they actually remembered.^[7]