Active recall vs rereading: what the research shows

What is active recall?

Active recall is any study activity where you have to produce the answer before you see it. Answering a flashcard, writing everything you remember about a lecture on a blank page, doing a practice problem without the worked solution open, explaining a process to a friend: all of these are recall. Rereading notes, highlighting a textbook and watching the lecture again are not, because the information is in front of you the whole time.

Researchers call this retrieval practice, and its benefit the testing effect. The idea is not that tests are good for grading. It is that the act of retrieving a memory changes it, making it easier to retrieve again later.

What the research shows

Three studies are worth knowing, partly because they are clear and partly because they are often misquoted.

Roediger and Karpicke (2006). University students read short science passages. In one experiment, some read a passage four times (study, study, study, study), some read it three times and took one recall test, and some read it once and took three recall tests. On a test five minutes later, the rereaders did best (83% vs 71% for the mostly-testing group). One week later the order flipped: the group that tested three times recalled 61% of the ideas, the group that reread four times recalled 40%. Rereading wins in the short term and loses when it counts.

Karpicke and Blunt (2011). Students studied a science text either by building a concept map with the text open or by practising retrieval (reading, then writing down what they could recall). On a later test that included inference questions, retrieval practice produced more learning, even when the final test asked students to draw a concept map.

Dunlosky and colleagues (2013). This review in Psychological Science in the Public Interest rated ten common techniques. Practice testing and distributed practice were rated high utility. Elaborative interrogation, self-explanation and interleaved practice were rated moderate. Summarization, highlighting and underlining, the keyword mnemonic, imagery for text learning, and rereading were rated low.

Why rereading feels like it works

When you reread a chapter, the words feel familiar. Familiarity is easy to confuse with knowing. You recognize the material when you see it; that does not mean you could produce it on a blank exam page. Highlighting has the same trap: it feels productive, it leaves a visible trace, and it requires very little memory work.

Recall feels worse. You get things wrong, you stall, you realize there are gaps. In the Roediger and Karpicke study, students who reread predicted they would remember more than the students who tested themselves. They were wrong. Treat the discomfort of recall as a sign you are doing the useful kind of work.

Active recall methods you can use tonight

Pick one or two and use them every week. None of them need special software.

• Blank page review. After a lecture, close your notes and write everything you remember for ten minutes. Then open the notes and fill gaps in a different colour. The gaps are tomorrow's study list.
• Flashcards with a real answer step. Say or type the answer before flipping. The StudyBrix flashcard decks have a Learn mode with typed answers and a Test mode with multiple choice, true or false and written questions.
• Question-first notes. Turn each heading in your notes into a question in the margin ("What are the three conditions for equilibrium?"). Cover the notes and answer the margin.
• Do problems closed-book. In math and science, attempt the problem with the solution hidden. Only check once you have committed to an answer or are truly stuck for several minutes.
• Explain it out loud. Teach the idea to a roommate, a pet or an empty room, without notes. Wherever you say "and then it sort of..." is where to look again.
• Practice tests under exam conditions. Old exams, end-of-chapter questions, or printable worksheets with the answer key set aside until you finish.

How to combine active recall with spacing

Recall works best when it is spread out. Testing yourself five times in one evening helps less than testing yourself once on five different days. A simple rule: the first recall the same day you learn something, the next one a day or two later, then a week, then two weeks. Our article on spaced repetition flashcards gives a concrete schedule.

One more finding to keep in mind: in Karpicke and Roediger (2008), students who kept testing themselves on items they had already recalled once remembered about 80% a week later. Students who stopped testing those items remembered about a third. Getting a card right once is the start, not the finish.

What about highlighting, summaries and mind maps?

You do not have to give them up. Use them as a step on the way to recall rather than as the study itself.

If you teach or tutor, the same principle works for younger students; see how to use worksheets for retrieval practice.

Does active recall work for every subject?

The testing effect has been found with word lists, science passages, foreign vocabulary and conceptual questions, and for learners of many ages. It is not limited to memorizing facts. That said, recall needs something to recall. If you do not understand a proof or a reaction mechanism yet, start by working through it carefully with the explanation open. Then close it and try to reproduce it.

For a short structured introduction, the retrieval practice lesson in our research and study skills course walks through these methods with exercises.