Why you can’t learn a language in your sleep

by Jakob Straub
January 27, 2021
woman in bed trying to study and prepare for sleep

It sounds like a language student’s literal dream: you put on headphones, go to sleep and in the morning, your language skills have improved. With advances in neuroscience and the way we understand the human brain, sleep learning surely must be just around the corner, right? Not so fast. We’ll explain how sleep and learning are connected, why some research results look promising, and why studying still yields the best results.

The science of learning and sleep

Sleep does play an important part in learning. Learning, memory and sleep are connected. Although the research is far from exhaustive, it shows that sleep affects your learning and memory in two ways. Most students will have experienced the first one: lack of sleep makes you lose focus and concentration so you’ll struggle with learning. The second way is more subtle: sleep also plays a role in memory consolidation.

In scientific terms, memory has three functions:

  1. Acquisition: introducing new information into the brain
  2. Consolidation: the process of forming stable memories
  3. Recall: conscious or unconscious access to stored information

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Sleep and memory

Acquisition and recall are commonly associated with wakefulness. Brainwave analysis indicates that memory consolidation happens as you sleep. While you’re catching Zzzs, your brain is talking to itself, strengthening neural connections to form stable memories. Your sleep exhibits different phases throughout the night, and scientists have reason to believe that these are connected to different types of memory as well.

Declarative memory is fact-based information, typically answering a “what” question such as “What is the capital of Germany?” Procedural memory is related to “how” to do something, a skill such as swimming or drawing. In tendency, the consolidation for declarative memory seems to happen during restorative slow-wave sleep, while REM or dream sleep is associated with procedural memory consolidation.

The important takeaway for learners is: sleep deprivation and low-quality sleep have a negative impact on your learning. Not only will it decrease your ability to receive new information, it also hinders memory consolidation.

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Is there learning without consciousness?

A lot of research focused on memory consolidation of knowledge acquired while being awake. But researchers at the University of Bern in Switzerland have shown successful vocabulary learning during slow-wave sleep. Test subjects were able to form new memories of words learned during sleep and to recall those unconsciously while awake. Their brains appeared to use the same structures for learning, whether they were awake or asleep.

The Interfaculty Research Cooperation “Decoding Sleep” demonstrated that a sleeping person is able to form new semantic associations between foreign words and their translation. During deep, slow-wave sleep, brain cells switch back and forth between an active and inactive state about every half-second. During the so-called up-state, brain cells are able to encode and store information.

These results show that the language areas of the brain and the hippocampus, which can be described as the essential memory hub, are able to manage memory formation, regardless of whether we’re unconscious or awake. In other words: memory formation does not require consciousness – you CAN learn new vocabulary in your sleep!

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Memories alone are not language learning

But before you throw away your course books and cancel your online language learning subscription, consider this: yes, this new evidence for sleep-learning has practical relevance. It’s a challenge to previous theories that memory formation was only possible during wakefulness. Sleep then appears to be a more fluid mental state than we might have thought in which we still have some possible connection to the wakeful world.

But keep in mind that these are experimental results. Only further research will show how deep sleep can be used to form new memories, and with what efficiency or possible side-effects. Rest assured there won’t be an app for you to download anytime soon, as disappointing as this might seem.

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Language learning is more than acquiring vocabulary

Besides, the “Decoding Sleep” research has only shown that you can acquire declarative memory during sleep, which lends itself to vocabulary learning but leaves out other aspects of language learning, the “how” of procedural memory.

  • Understanding and learning grammar is more complex than fact-based knowledge. You have to see things in context and understand the relationships of words in full sentences.
  • You need to experience pronunciation. Sleep learning could possibly teach you to recognise a word when it’s properly pronounced, but you have to speak it yourself again and again also.
  • So far, sleep learning experiments use audio cues for teaching new words. For now, this completely leaves out spelling.
  • Sleep learning is passive; you’re unconscious, after all! There’d be no way to experience the interactivity of a classroom where you learn from mistakes when an experienced teacher corrects you.
  • Sleep learning research demonstrated unconscious recall of memories and test-like recall. A vocabulary is different from your brain trying to find the right word as you construct a sentence. Further research will have to show how accessible sleep-acquired knowledge is in everyday situations.

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Tips for knowledge retention for language learners

There you have it: the truth is that despite promising results and new learning theories, sleep learning is far from being a technology that’s on its way to a mass market. However, we want to end on a positive note and leave you with tips on how you can harness the connection between sleep and learning for improved knowledge retention today! Improve your language learning with these simple steps:

  • Your learning will be more efficient when you’re well rested. Show up fresh for class or study sessions and schedule a short nap beforehand if you have to. Exhaustion and sleep deprivation will severely hamper your learning.
  • Make sure you get sufficient quality sleep every night and especially after days of learning to enhance memory consolidation. Most adults need seven to nine hours of sleep, so don’t skimp. Also, try to rest your brain for a bit after class or studying and don’t dive into another high mental activity or a distraction such as social media. You’ll literally push what you just learned out of your mind again!
  • The sooner you put the information into practice after learning, the more you’ll retain.
  • Recapitulation is key for knowledge retention, but even better is teaching: explain what you’ve learned to a fellow learner and you’ll remember it better.
  • When you re-expose yourself to what you’ve learned at just the right moment, you’ll maximise retention. The so-called “Forgetting Curve” is the principle of spaced repetition. Ensure that you revisit what you’ve learned at least five times over a couple of weeks after acquisition to boost retention.

Want to know how else you can improve your language learning skills? Here are five good habits to start when learning a language!

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