neur.ro

Spacing and retrieval practice

method · origin: study · evidence: strong

In short

Two of the best-documented findings in the psychology of learning go together:

Both share the same trap: in the moment, the weaker option feels better. Rereading and cramming give a feeling of knowing, but the memory lasts less.

What it says

Testing beats rereading, but not right away. Roediger and Karpicke (2006) gave students short texts to read, about the sun or about sea otters. After a first reading, some of them reread the text, and the others wrote down everything they remembered from it, without being given any correct answers. The final test came after 5 minutes, 2 days or a week.

In the first experiment, after 5 minutes, those who had reread remembered slightly more: 81% versus 75%. After 2 days, the situation reversed: 68% for those who had been tested, versus 54%. After a week: 56% versus 42%. After a week, the tested students remembered about as much as those who had reread remembered after only 2 days.

The second experiment went further, with four 5-minute sessions:

After 5 minutes, those who read the text 4 times recalled 83%, versus 71% for those who read it once and tested themselves 3 times. After a week, the order reversed: 40% versus 61%. How much of the text they recalled after four 5-minute sessions Test after 5 minutes read 4 times 83% read 3, test 1 78% read 1, test 3 71% Test after a week read 4 times 40% read 3, test 1 56% read 1, test 3 61% Rereading wins today; testing wins a week later.
Data from Roediger and Karpicke (2006), Experiment 2: 180 students, 30 in each condition. The percentages show the share of the text's ideas they recalled.

One important detail: those who had read the text four times were the most confident that they would remember it a week later. They were exactly the ones who remembered the least after a week.

The result is not isolated. The meta-analysis by Adesope, Trevisan and Sundararajan (2017) compared practice tests with other ways of learning and found that tests produced better results than rereading and than every other option compared. The size of the effect varied with the type of test, the participants and how the studies were run.

Spacing: it depends how long you want to remember. Cepeda and colleagues (2006) gathered 839 measurements from 317 experiments, published in 184 articles. They found that the optimal gap between sessions grows the longer you want to remember the material.

A later study by the same team (Cepeda et al., 2008) measured this directly, with more than 1,350 participants. They learned a set of facts, got a review after a gap of up to 3.5 months, and took a final test up to a year after that. The optimal gap was about 20–40% of the time until the test when the test was a week away, and 5–10% when it was a year away. Our own arithmetic from these proportions: for a test in a week, the ideal review comes after about 1.5–3 days. For something you want to remember for a year, after about 2.5–5 weeks.

The overall assessment. Dunlosky and colleagues (2013) evaluated ten learning techniques used by students. Only two received a high-utility rating: practice testing and distributed practice, because they help people of different ages and abilities, on many kinds of assessment, including in school. Rereading and highlighting, though among the most used, received low utility.

Example

An example built for this text: you have to learn 40 new terms for an exam in two weeks. The usual approach is to read the list a few times the night before the exam. The approach the studies support: today you learn them and cover the definitions to try to recall them. A few days later, you again try to recall each definition before looking. You repeat once more a few days before the exam. The total time can be the same. The difference is how and when you use it.

How to apply it

The steps below are a practical approach we propose, based on the studies cited.

  1. Close the book and try to recall. Write down or say out loud everything you know about the topic, then check. In Roediger and Karpicke, testing helped even without the correct answers, but checking keeps you from remembering mistakes.
  2. Split your studying into several sessions. The same number of hours spread over several days gives better results than one long session.
  3. Match the gap to the deadline. The longer you need to remember, the longer the gaps between reviews can be. As a starting point, use the proportions from Cepeda et al. (2008).
  4. Don’t trust the feeling. Rereading feels more effective. Kornell and Bjork’s (2008) participants rated cramming as more effective even after their own results had shown the opposite.
  5. Use flashcards or spaced-repetition apps. They combine both ideas: they ask you to recall the answer and schedule reviews at growing intervals. The specific apps were not tested in the studies here.

Limits and nuances

Sources

See also: Implementation intentions