Short answer
Sometimes, but mostly no. Healthy sleep is essential for memory! Whether memory can be influenced externally during sleep is a hot topic of research. There is no evidence that completely new information can be memorized during sleep. It may be possible however to reinforce the memory of something that was already learned before falling asleep. But beware: trying to memorize something as complex as an entire text during sleep might not be effective and can disturb your sleep.
Longer answer
Memory is the ability of our brain to store and retrieve information over time. It involves three processes: memory formation (encoding) – memory consolidation (stabilizing) and memory retrieval (remembering). Memory can be classified in various ways, depending on the focus of the research (see the answers to previous BrainHelpDesk questions: ‘Why do some people remember things better than other people’ and ‘What happens when you have a blackout during an exam’). In cognitive science we often divide memory into two different types: implicit and explicit memory. Implicit memory is a more automatic way of storing information, which doesn’t require conscious awareness. Think of habits and skills such as driving or playing the piano, which eventually require no voluntary effort to remember. Explicit memory involves information about facts or events that can be reported verbally, which is why it’s a lot easier to test: you just ask someone whether they remember something.
When you’re listening to information that you would like to learn while you’re sleeping, you are trying to influence explicit memory formation. Unfortunately, explicit memory formation and sleep turn out to be terrible bed partners. A review that analyses several articles that tested this found no evidence that new information heard during sleep can be remembered after waking up. A notable exception is when the information itself is what wakes you up (think of a loud voice from an audiobook)! But obviously that doesn’t count as sleep learning. What is interesting however, is that there is evidence for implicit memory formation during sleep. An example of this is a study where researchers presented the smell of cigarettes and the smell of rotten fish simultaneously to sleeping smokers. After this, a large proportion of smokers cut down their smoking for several days.
So explicit memory formation (the creation of new memories) doesn’t work when you’re asleep, but implicit memory formation does. What about explicit memory consolidation? What if you learn a text during the day and then play it again while you sleep? A review (in which researchers looked at many studies) found compelling evidence for explicit memory consolidation during sleep! This means that if you’ve been cramming a couple of French words as part of your homework before dozing off, you may actually benefit from hearing it again while you’re sleeping. Do note that this has only been shown to work for very simple associations (between single words and sounds or smells for example). It’s unlikely that we would be able to learn entire texts while sleeping, even if we’ve heard those texts before while we were awake. An open question is whether these memory-consolidation processes that happen in our brains while we sleep actually make it into our dreams. In other words: do we need to dream of something to remember it better later? Our laboratory at the Netherlands Institute for Neuroscience in Amsterdam, focuses on finding answers to questions like this one.
Benefits of sleep rehearsal across different tasks (explicit memory formation). When you’re listening to a complex text that you’ve been trying to memorize before, there is no improvement the next day. However, if you’re trying to learn a very simple task, such as the association between a specific cup and a sound. Replaying the sounds while you’re asleep will actually improve your performance the next day! This illustration was created by Inès Ben Haj Kacem.
A side note on memory tasks: In cognitive science, we often want to stick to scientific rigor. We need to simplify complex tasks that involve memory and creativity. For example, we test the number of word-image pairs or the number of round objects you can think of on the spot. Not the most engaging of tasks… These tasks are often quite different from the way we use memory and creativity in our natural and rich everyday lives. Scientists are increasingly trying to make their experiments more realistic (and fun!), to explore and comprehend these processes outside of the lab.
Read more?
Somayeh Ataei, Eni Simo, Mathijs Bergers, Sarah F. Schoch, Nikolai Axmacher, Martin Dresler. Learning during sleep in humans – A historical review. Sleep Medicine Reviews, Volume 72, 2023, 101852.
Hu X, Cheng LY, Chiu MH, Paller KA. Promoting memory consolidation during sleep: A meta-analysis of targeted memory reactivation. Psychol Bull. 2020 Mar;146(3):218-244.
Thomas Schreiner, Björn Rasch, Boosting Vocabulary Learning by Verbal Cueing During Sleep, Cerebral Cortex, Volume 25, Issue 11, November 2015, Pages 4169–4179, https://doi.org/10.1093/cercor/bhu139
Mutti C, Siclari F, Rosenzweig I. Dreaming conundrum. J Sleep Res. 2025 Apr;34(2):e14338. doi: 10.1111/jsr.14338. Epub 2024 Oct 3. PMID: 39360736; PMCID: PMC11911046.