Testing yourself beats re-reading

In one line: trying to remember something you’ve read does more to help you keep it than reading it again, even though reading again feels better at the time.

What they did

Henry Roediger and Jeffrey Karpicke are memory researchers in the USA. They asked a simple question: after you’ve read something once, what should you do next? Read it again, or close the book and try to write down what you remember?

They ran two experiments with university students. Each student read short passages of factual writing.

• In the first experiment, after reading a passage, some students read it again. Others spent the same time writing down all they could recall, with no help and no answers given. Students were then tested after 5 minutes, 2 days or a week.
• In the second experiment, there were four short sessions. One group read the passage four times. Another read it three times and tried to recall it once. A third read it once and tried to recall it three times. They were tested after 5 minutes or after a week.

What they found

• Re-reading won in the short term. Tested after 5 minutes, the students who had re-read did better.
• Recall won after a delay. By 2 days, and again at a week, the students who had practised recalling remembered more. The lines crossed.
• More recall beat more reading. In the second experiment, after a week, the group who read once and recalled three times remembered about 61% of the passage. The group who read four times remembered about 40%.
• People guessed wrong. The students who read four times felt the most sure they’d remember it. They remembered least a week later. Feeling that you know something is not a good guide to whether you’ll keep it.

How much should you trust it?

Strong, well-repeated evidence in the lab and the classroom; less tested at work.

• These were careful, controlled experiments. The finding has since been repeated many times, by other teams, with other materials.
• The students learned short passages of facts. That’s not the same as learning a hands-on skill, or applying knowledge to a new patient. The wider research is more mixed on those.
• No answers were given after the recall attempts. Later research shows the benefit is larger when people get the right answer afterwards.
• There is little direct testing with healthcare staff learning at work.

If you need to convince someone

In our words (a paraphrase, not a quotation): trying to remember helps people keep more than going over it again does, and the benefit shows up most when you test them after a delay.

What it means for you

1. Open with “What do you remember from last time?” Let people try, then go through the right answer together. Use it in place of a recap slide.
2. Swap some re-reading for recall. If people review notes before a shift or a session, suggest they close the notes and try to recall the key points first, then check.
3. Follow up with a question, not the slides. A single question a day or two after a session, such as “Without looking, what are the three checks?”, is likely to do more for remembering it next week than sending the slides round.
4. Don’t trust the nodding. People who feel sure they’ve got it may not keep it. A quick check of what they can recall tells you more.

How it appears in Teaching That Lands

Session 2 opens with people showing what they did with their Session 1 ask. Then comes a quick quiz on Session 1, a week after they learned it, before anyone names why. Only then is it called retrieval practice.

Next, half the room re-reads a sheet of made-up words and half test themselves on it. A surprise retest later in the session often shows little difference, or even a win for re-reading, just as this study found at 5 minutes. Session 3 opens with the same retest, a week on.

The small print

• The first experiment’s delays were 5 minutes, 2 days and 1 week; the second, 5 minutes and 1 week. The 61% and 40% figures come from the second.
• Recall tests here were “free recall”: write down all you can, with no cues. Multiple-choice quizzes also help, but the size of the benefit varies with the type of test.
• Later work by Kornell, Hays and Bjork (2009) found that even a failed attempt to recall helped, as long as the learner was then shown the right answer.
• Why it works is still debated. One idea is that each time you dig something out, it gets easier to find next time. Researchers have several competing explanations.
• Reviews that pool many studies of this kind may overestimate the benefit, because studies that find nothing are less often published.
• A related paper in Science (Karpicke & Roediger, 2008) found that, for learning foreign-language word pairs, practising recall was what helped people keep them a week later. Extra studying added little.