Sleeping Between Study Sessions Improves Memory Recall

New findings published in the journal Psychological Science from the Association for Psychological Science notes that sleeping in between study sessions may make recalling what you have studied easier, even up to six months later.

Stephanie Mazza, psychological scientist at the University of Lyon, notes that these results show sleeping in between study sessions has a twofold advantage, with the reduction of extra time that would need to be spent relearning the information while also ensuring better long-term retention.  This is more effective than repetitive practice alone.  Further, she notes that studies in the past have shown sleeping after studying is a good strategy, but these new findings suggest that sleeping in between two sessions improves the strategy.

There are separate studies that show both regular sleep schedules and practice repetition improves memory; however, very little in the way of combining the two has been reviewed.  Ms. Mazza and the other scientists in the study hypothesized that between-session sleeping may make relearning the information easier, which would reduce the effort and time needed to commit that information to long-term memory.

In this study, a total of 40 French adults participated.  Each person was randomly assigned to either the “wake” group or the “sleep” group.  The first study session included all participants, each of whom were shown 16 French-Swahili random word pairs.  They were allowed to study the words for 7 seconds, after which the words disappeared and only the Swahili word was shown to them.  They then had to recall which French word matched the Swahili term.  The correct word pair was shown for 4 more seconds, and any words that were not translated correctly were shown again until all word pairs were given back correctly by participants.

The participants repeated the recall task 12 hours later by practicing the entire list of words until all pairs were translated correctly.

Some of the people in the study completed both sessions within the same day, with the first session happening in the morning and the second session in the evening.  This was the wake group.  The others in the study, the sleep group, completed the first session in the evening, went to sleep, and then did the second session the next morning.

In the first session, both groups showed little difference in their ability to recall the words or the number of times they needed to see the words to retain the pairs in memory.  However, 12 hours later, the data showed something very different.  Those in the sleep group were able to recall an average of 10 of the 16 word pairs.  Those in the wake group recalled an average of 7.5 words.  Relearning data was different as well.  The sleep group participants only needed three trials to remember all 16 word pairs, while the wake group needed 6 trials.

In the end, all participants were able to recall all the word pairs; however, it is notable that the sleep group was able to do this in less time with less effort than those in the wake group.

Ms. Mazza notes that the sleep group participants seemed to have some sort of memory transformation.  This transformation made it possible for participants to re-encode the information more quickly during the relearning session, which saved them a good amount of time.

The sleep group’s retention and ability to recall words lasted over time.  A followup interview showed that those in this group were able to recall more words than those in the wake group a week later.  The sleep group participants did not have too much trouble with forgetfulness and were able to recall an average of 15 word pairs.  The wake group, on the other hand, could only recall about 11 word pairs.  This was still noticeable six months later.

It is notable that sleep benefits in this study could not be ascribed to quality or level of fatigue, or to their long- and short-term memory capacity.  Both groups showed equal measures in these components.

The importance of these findings is profound, especially for teens and college students.  Alternating study sessions and sleeping in between may be an effective way to better retain the information over a longer period and with less effort.



Rachael Herman is a professional writer with an extensive background in medical writing, research, and language development. Her hobbies include hiking in the Rockies, cooking, and reading.


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