Learning Asleep
The nuanced relationship between language-learning and sleep
Image by: Aleksandar Cvetanovic
By Hanyu Tales (20th March 2025)
Learning a language while you sleep sounds like the ultimate productivity hack, but the relationship between sleep and language-learning is a nuanced yet well-researched topic within the fields of linguistics and neuroscience. In this article, we will take a look at multiple studies to determine exactly how sleep affects language learning, whether we can learn a language in our sleep, and which strategies we can employ to gain the maximum benefit from these findings.
Deep sleep and Grammar
Research and intuition has consistently shown that deep sleep aids in memory consolidation. This is discussed in an article in the Brain and Language journal, which also added that language cues are replayed during sleep as part of this process. Given that repetition is vital for cementing grammatical structures, this could explain why a different study found that deep sleep was crucial for consolidating new grammar. This idea was expressed in an article found in the scientific journal Neuropsychologia, which shared these findings from an experiment looking at sleep’s effects on learning new language rules:
“Greater [SWS⁎REM] durations predicted increased post-sleep sensitivity to the rule. […] Slow-wave and REM sleep contributed to stabilization of new linguistic knowledge.”
In other words, the more time someone spent in deep sleep after studying a new language rule, the better they did at remembering that rule after waking up. Naps and Vocabulary
The same experiment mentioned in Neuropsychologia also found that while deep sleep is vital for consolidating new rules, short naps were great for remembering new words. Another study looking at how sleep affected learning new words in a made-up language found that for the brain to make arbitrary mappings (such as memorising words from a vocabulary list), students taking a nap after learning performed better than those who did not. 
Meanwhile, a study on infants found that those who napped after learning remembered new words better than those who stayed awake. However, remembering new words is not the only thing a nap may support, as this paper revealed that naps also help with understanding where phonemes appear in syllables, meaning speech improvements. It seems that the carb-induced afternoon nap you look forward to everyday may be productive after all, as it could be helping you to both remember and produce new vocabulary.
Image by: Oladimeji Ajegbile
Sleep Disorders
While this article is not a sleep hygiene guide, it is worth remembering that for some people, naps make it difficult for them to fall asleep later on. While naps may benefit vocabulary acquisition, this certainly does not outweigh the benefits of good sleep to every single aspect of life. Furthermore, in Abby Eagle’s book: How to Put Insomnia to Sleep, one of the potential causes for insomnia she gives is “an overactive mind”. This suggests that if you are aiming to benefit from the aforementioned memory consolidation power of sleep by studying before bed, it is crucial to take it easy and ensure it is a somewhat relaxed study session. It goes without saying, but poor sleep not only worsens your health, but also makes language learning tougher, as stated in this article:
“Both children and adults with sleep disorders were at a higher risk for language problems than heathy sleepers.”
Learning During Sleep
This sub-topic was saved for last for the simple reason that focusing on high-quality sleep so you are energized for the study sessions taking place while you are awake is what matters most. However, there is some research suggesting that bold claims about having learned a language while sleeping may not be completely false. This study found that your brain can still process sounds and language-related input during sleep, especially in the lighter stages of sleep (non-REM). This suggests that the reported benefits people receive by falling asleep listening to content in their target language may not be placebo. Furthermore, this paper claimed:
“Our results indicate that verbal cues presented during NonREM sleep reactivate associated memories, and facilitate later recall of foreign vocabulary without impairing ongoing consolidation processes.”
This is in line with earlier research suggesting light sleep (like that experienced during naps) helps with learning new words, but it also adds that hearing previously learned words during sleep may make them easier to recall later. Yet, despite these two papers offering interesting insights, as well as the existence of further research on this topic, we struggle to recommend potentially disrupting your sleep by recreating these conditions for yourself. Practical Tips
So what can we take from all this? Here is a quick summary:
- Review content before sleeping: Reviewing words or vocabulary before bed may prime your brain to strengthen the connections needed for you to recall them when you wake up.
- Short naps may help: Napping certainly carries benefits for language learners, especially when it comes to remembering new words. However, make sure your napping habit it is not at the expense of a good night’s sleep.
- Do not study difficult content right before bed: An overactive mind may contribute to insomnia—stick to reviews and comprehensible input close to bedtime.
- Be careful with “learning while you sleep”: While there is some research suggesting there could be something to it, it goes against what most sleep experts recommend for a good night’s sleep.