To retain information in the long term, we know that it is important to test our knowledge and repeat it. But what is the ideal frequency of revision to avoid memory lapses on exam day? Psychological research gives us some keys to better organize ourselves.

The proverb “Practice makes perfect” reflects the importance of repeating the same activity in order to master the skills. This principle also applies to the vocabulary or lessons we must assimilate. To counter our natural tendency to forget information, it is essential to reactivate it in memory.

But, precisely, how often should we organize these reactivations to anchor knowledge in our memories as effectively and sustainably as possible?

Research in cognitive psychology provides some answers to this question. Beyond ready-made recipes, it is important to understand the principles underlying sustainable learning in order to appropriate them and be able to use them personally.

Relying on the “spacing effect” in revisions

There are two main principles that are fundamental to memorizing information over the long term .

The first is to use tests to learn and revise  : it is much more effective to self-test on content, for example using question-answer cards, than to reread it . And, after each attempt at memory retrieval, the information not recalled must be re-studied .

The second principle is to distribute reactivations well over time. This is the “spacing effect”  : if you can only dedicate three sessions to a content, it is better to schedule them at relatively long intervals (for example, every three days) rather than short ones (every day).

Revisions spaced out over long intervals will require more effort: it will be a little more difficult to retrieve the information from memory after three days than the next day. However, it is precisely these efforts that will strengthen memories , promoting long-term retention.

In learning, we must be wary of ease. Easily remembering a lesson today is not a good indicator of the likelihood of remembering it in a month. However, such a feeling of ease can lead us to consider (wrongly) that it is useless to revise it.

Robert Bjork of the University of California called “desirable difficulty” the idea of ​​an optimal level of difficulty, located between two extremes. The first extreme corresponds to very easy learning (but ineffective in the long run) while the other extreme corresponds to learning that is too difficult (both ineffective and discouraging).

Finding the right study rhythm

There is therefore a limit to the spacing between reactivations: after a long delay (for example a year), learned information will have strongly declined in memory and will be very difficult, if not impossible, to recover. In addition to generating a negative emotion, this situation will force us, in a way, to start learning again from the beginning and the previous efforts will have been in vain.

It is therefore a question of finding the right interval between reactivations , neither too long nor too short. But this right interval is not a universal value because, in reality, it depends on several factors (related to the individual, the information to be learned and the history of this learning). Some learning software implements algorithms that take these factors into account, which allows them to test each piece of information at the “ideal” moment .

There are also paper and pencil methods. The simplest is to follow an “expansive” program, that is, using increasingly longer intervals between successive sessions . This technique is implemented in the “J method”, known to some students. Its effectiveness lies in the progressive strengthening of memory.

At the beginning of learning, a memory is fragile and requires rapid reactivation in order not to be forgotten. With each new reactivation, the memory is strengthened, which allows the next reactivation to be delayed, and so on. The other consequence is that each reactivation is then moderately difficult, and therefore located at the “desirable” level of difficulty.

Here is an example of an expansive schedule for a given content: D1, D2, D5, D15, D44, D145, D415, etc. Here the duration of the interval is tripled from one session to the next (24 hours between D1 and D2, then 3 days between D2 and D3, etc.).

Gradually integrate new knowledge

There is no scientific consensus on the best series of intervals. However, it seems particularly beneficial to perform the first reactivation the day after (D2) of the initial learning because the night’s sleep will have allowed the brain to restructure and/or reinforce the knowledge learned the day before (D1). The following intervals can be adjusted according to each person’s constraints.

Finally, the method is flexible: if necessary, a session can be postponed a few days before or after the scheduled date without impacting the overall effectiveness in the long term. The important thing is the principle of regular reactivation.

The expansive program also has a considerable practical advantage: it allows new information to be integrated gradually. For example, a new content can be started on D3 of the above program, since that day does not contain a session. By adding content gradually in this way, it is possible to memorize a very large amount of information in a lasting way without increasing the time spent studying it tenfold.

The other method is based on the principle of “Leitner boxes” . This time, the duration of the interval before the next reactivation is not planned in advance but depends on the result of the memory search. If the answer was easily retrieved, the next reactivation will be in a week. If the answer was found, but with difficulty, we will wait three days before testing ourselves again. If we have not managed to find the answer, the next test will take place the next day. Everyone, with experience, will be able to adjust these intervals and develop their own system.

In short, for effective and lasting learning, you must make the effort to retrieve the information from your memory and repeat this process regularly, at suitable intervals to prevent forgetting.

Author Bio: Emilie Gerbier is a Lecturer in Psychology at Côte d’Azur University