I have read now several times as a "secret tip" that learning directly before going to sleep significantly increases the effectiveness of learning, probably the long-term memory when, for example, learning the vocabulary of a new language.

The Costa de Valencia Spanish language web site states:

Before going to sleep, you should repeat the new material again for 10-15 minutes, that brings success while sleeping. At night your subconsciousness especially deals with the final experience of the day. Thus the new knowledge will be strengthened without your influence.

The psychological explanation sounds a bit like amateur Freudian psychology ("subconsciousness") to me, but I don't find it convincing or consider it to be common knowledge (at least I'm not aware of a psychological law/study strengthening this method). Also, one could understand the statement as: It only works when you learned the words already once during the day and then repeat them again briefly before going to sleep.

So, is it the repetition in conjunction with sleeping, or generally learning briefly before going to sleep, that causes this increased effectiveness?

What evidence exists proving the effect of this learning method? And what is the exact rule/framework to use this method/law correctly, repetition, and duration (e.g., min/max. 10-15 min.)?

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    I have heard that sleep is required for learning because short term memory is converted into long term memory during sleep.
    – Sam I Am
    Nov 26, 2011 at 3:30
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    I have also heard the opposite claim: That one should study first thing in the morning so the material will be recalled throughout the day, rather than forgotten immediately upon sleeping. But I'd prefer if studying immediately before sleep is the actual preferred method, because I am not a morning person! :)
    – Flimzy
    Nov 26, 2011 at 18:45
  • @Sam I Am: yes, this is a commonly accepted theory. Nov 28, 2011 at 20:21
  • Back when I was required to learn poems by heart, I noticed that I can repeat it for hours during the day and still not remember it in the evening, but after I sleep I can suddenly remember most of it in the morning. For long poems this effect was obvious every day that I learned it.
    – RomanSt
    Nov 28, 2011 at 20:46

2 Answers 2


The website you quote makes it sound like the subconsciousness is a little man in your brain, with a book of knowledge, reviewing all the material during the night and "strengthening knowledge without your influence". Although the website doesn't properly support the idea about how post-training sleep might benefit memory consolidation, it does convey some "truth".

Gais et al. 1 studied the timing of learning, sleep and subsequent recall, and indeed found that when learning is immediately followed by sleep, this improves subsequent recall as compared to conditions in which learning was followed by wakefulness.

The task involved learning German words. In the picture below you can see the different conditions that were tested. In the first experiment (A) Gais tested whether sleep following learning or wakefulness following learning enhanced the consolidation of declarative memory (morning vs. evening). When comparing the different conditions, the evening-learning condition revealed a better performance than the morning condition.

To control for time-of-day effects a second experiment (B) was conducted, consisting of 2 evening conditions. One evening condition where learning was immediately followed by sleep and another evening condition where sleep was postponed until the morning hours. Again results favoured learning when it was immediately followed by sleep. Different learning-sleep-recall conditions
(source: cshlp.org)

Some mechanisms by which the role of sleep following learning (and the role of sleep in learning in general) might be explained are "memory replay" during sleep (neuronal activity reflecting the learning of a certain task during the day, re-occuring during the night), and/or synaptic downscaling (the synaptic homeostasis hypothesis).

The synaptic homeostasis hypothesis... predicts that sleep may enhance performance by global downscaling...

For more background information read the review of Tononi & Cirello 3, or a recent review by Ribeiro 4.

Now... what about these 15-20 minutes? Well I don't know where this advice comes from and don't know about scientific support for this claim. In the study of Gais the duration of learning (although not exactly mentioned) was "a few hours". I would say they are advantages and disadvantages to a learning period of 15-20 minutes as opposed to a longer learning period.

15-20 minutes rehearsal seems ideal in the sense that you'll be focusing on a limited amount of information. Strengthening this limited amount of information might increase their chances of being retained (I think this idea could be integrated with the synaptic downscaling hypothesis). When keeping study time or learning time shorter you might be able to increase focus. Keeping focus for a long time is more difficult and the efficiency by which one learns might decrease. However, you can also choose to learn for a longer time on a limited amount of information, thus increasing repetition and again increasing chances of the information being retained. It more or less depends on how you spend the time learning...

In addition, the above mentioned claims might depend on what type of information you want to retain. Studies might report contradicting results, depending on what type of material is to be learned. E.g. complex material requires more investment. Also learning requires time... one has to invest in understanding the material and there are different strategies by which one can try to learn material that aren't covered in the studies.

Personally I believe studies related to learning and sleep are really interesting to decipher what happens to the information we collect during the day. What happens during the part of the day where we are the least conscious of what's happening around us? When it comes to learning in itself however... I think it's more important to think about "how" you learn the material and how often you repeat learning the material, than the timing of learning in relation to sleep (e.g. paper on memory retrieval by Karpicke and Blunt 4).

  1. Gais, S. (2006). Sleep after learning aids memory recall. Learning & Memory, 13(3), 259–262. doi:10.1101/lm.132106 http://learnmem.cshlp.org/content/13/3/259.abstract (open access)
  2. Tononi, G., & Cirelli, C. (2006). Sleep function and synaptic homeostasis. Sleep Medicine Reviews, 10(1), 49–62. doi:10.1016/j.smrv.2005.05.002 http://www.maths.tcd.ie/~mnl/store/TononiCirelli2006a.pdf
  3. Ribeiro, S. (2012). Sleep and plasticity. Pflugers Archiv : European journal of physiology, 463(1), 111–120. doi:10.1007/s00424-011-1031-5 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256318/ (open access)
  4. Karpicke, J. D., & Blunt, J. R. (2011). Retrieval practice produces more learning than elaborative studying with concept mapping. Science (New York, NY), 331(6018), 772–775. doi:10.1126/science.1199327
  • I would say recalling and learning are very different things. Would the subjects who slept recall the German words better after a month?
    – nico
    Oct 13, 2012 at 18:12
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    Hi Nico, how are learning and recall different things? There are different ways of measuring learning, e.g. amount of forgetting, amount of remembering, you can compute it relative to the total amount of to be learned material... E.g. in machine learning, learning is defined by Tom Mitchell as "a computer program is said to learn from experience E with respect to some class of tasks T and performance measure P, if its performance at tasks in T, as measured by P, improves with experience E". This performance measure P could be considered as recall here.
    – smoens
    Oct 14, 2012 at 8:50
  • With regard to your comment about recall after a month. That's a valid comment. Maybe the difference between the two groups disappears after a month. This might depend on the forgetting curve, if the forgetting curve is the same for the two groups, you would still expect the group who remembered more in the first place, to also remember more at the later time point, unless forgetting is so high that they have both reached a minimum. If the forgetting curve of the group without sleep after learning is less steep, than the differences might disappear as well.
    – smoens
    Oct 14, 2012 at 8:53
  • I meant that remembering a word after a day is not the same thing as having permanently learnt it. I am not really an expert in the field, but -from what I recall (no pun intended)- the molecular/cellular processes of "fixation" of short and long term memories are different.
    – nico
    Oct 14, 2012 at 10:34
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    I think it's a good question whether the neural substrates of long term versus short term memory are different, a question I can't answer. It might come down to synaptic strength. So perhaps it's a matter if so-called long-term potentiation ("long-lasting enhancement in signal transmission between two neurons" en.wikipedia.org/wiki/Long-term_potentiation) is obtained or not. If the synaptic homeostasis theory is true (which is currently being investigated), this might favour sleeping after learning, but thus this is all speculative, and thus I can't really answer your question/concern.
    – smoens
    Oct 14, 2012 at 12:22

This paper (PDF) seems to indicate a "post-training" nap has beneficial effects on adults learning a new skill - Sleep Dependent Learning: A Nap is as Good as a Night, Mednick, S., Nakayama, K., Stickgold, R.

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    This paper argues that sleep sometime after learning something is helpful, and in fact a short sleep is effective as a long sleep. It does NOT address the question though: is the timing of the learning prior to sleep important? (Also, you might like to mention a full citation of this paper, given it isn't just some report from a bunch of uni students, but a paper published in Nature Neuroscience, a prestigious journal.)
    – Oddthinking
    Nov 29, 2011 at 4:11

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