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In the modern economy, efficiency is the name of the game. The drive to make the most of each minute of the day has incited tremendous interest in making sleep more productive. But the idea of learning during sleep is nothing new; in fact, a device known as the Psycho-Phone was patented in the 1930s and promised to boost confidence and prosperity by playing positive recorded messages while a person slept.

While the Psycho-Phone was marketed with dubious and over-the-top claims, recent research indicates that its basic idea of learning during sleep — known as hypnopaedia — may not be so far-fetched. In today’s society, hypnopaedia has received renewed focus in academic research that continues to refine our understanding of what happens in the brain during sleep.

This comprehensive guide reviews all that you need to know about hypnopaedia. It covers the basics, including the definition of hypnopaedia and a summary of the research that’s been conducted to date, and goes further in explaining how to apply that research to your own learning and how the field of hypnopaedia may continue to develop in the future.

What is Hypnopaedia?

Hypnopaedia has a straightforward definition: learning during sleep or hypnosis. According to the Merriam-Webster Medical Dictionary, it may also be written with the spelling hypnopedia or referred to as sleep-learning.

It is well-established that good sleep promotes better brain function, cognitive abilities, and memory. For this reason, sleeping itself is a way of encouraging better learning. However, hypnopaedia is more than just getting good sleep. Instead, it is an attempt to provide some type of instruction during sleep that empowers learning. In this way, it tries to expand upon the general cognitive benefits of sleep.


Is it Possible to Learn While You Sleep?

Researchers believe that one of the important functions of sleep is to promote the health of the brain. This includes consolidating and organizing information in memory, strengthening communication between brain cells, and purging both toxins and unnecessary information. All of these processes can contribute to better mental performance and learning.

Hypnopaedia tries to capitalize on this brain activity by stoking the brain with certain stimuli during sleep to promote even more learning. In the 1920s and 1930s, people reported positive results using devices like the Psycho-Phone. But sleep science has come a long way since that time, including the development of electroencephalography (EEG) in the 1950s. The EEG allows brain activity to be monitored during sleep, and it let researchers see that participants in hypnopaedia research who described learning new information had not actually been asleep during the studies. Though that early research was tossed aside, in the last 10-15 years a renewed focus on sleep research has taken new approaches and started to explain how hypnopaedia works.

One way that hypnopaedia can work is through conditioning. In one study, researchers in Israel found that people who were sleeping could be taught to associate specific sounds with pleasant or foul smells. The study participants were exposed to these sounds and smells while asleep but remembered the association upon waking up. The effect took place regardless of the sleep stage during which the conditioning occurred.

Researchers in Paris found that the brain can process words when sleeping. People in the study were taught to have a specific reaction upon hearing certain words, and those reactions were triggered upon hearing those words while asleep. In this study, the responses to the words were initially learned while awake, meaning that although the brain was able to conduct linguistic processing during sleep, it wasn’t actively learning new information.

At Northwestern University, cognitive research demonstrated that sleep could be deployed to help with problem solving. In their study, people worked on a puzzle while hearing specific sounds. During sleep, those same sounds were played, and when they woke up, the participants were more likely to be able to solve puzzles that they had been unable to solve before going to bed. The sound cues appear to have encouraged the brain to effectively process and reorganize information as a person was sleeping in order to facilitate more complex problem-solving later.

Other types of cues, such as the smell of roses, have been deployed to promote better learning from sleep as well. In addition to problem-solving tasks, cues have been found to improve memory and even process-oriented skills such as learning a melody to play on the piano. In one well-publicized study, this cue-based method of hypnopaedia was even effective in reinforcing lessons learned during prior training to combat race and gender bias.

In the majority of these studies and other similar hypnopaedia research, sleep has been used to reinforce information that has already been examined and digested while awake. In general, experiments been limited in permitting people to receive and remember completely new information while asleep.


How Can You Use Sleep to Enhance Learning?

If you’re a student hoping to ace your next test, an employee preparing for a big meeting, a traveler studying a new language, or a musician learning a song, you may be looking for ways to maximize your time. One way of trying to do so is by optimizing your sleep to promote learning.

Hypnopaedia isn’t a shortcut. It’s not a way to gain new knowledge or skills immediately and without effort. However, when properly deployed, it may give a boost to your studying and learning. If you’re looking for concrete steps to use sleep to enhance learning, try the following approaches.

Start With Good Sleep

Getting enough quantity and quality of sleep is a key building block to learning. Even without other hypnopaedia techniques, sufficient sleep facilitates the brain’s ability to learn, remember, and analyze information. On top of that, meaningful sleep is necessary to allow hypnopaedia to work in the first place. Don’t cut your sleep short in order to cram for a test or pull an all-nighter on a project; it’s just not worth it.

Adults should aim for 7-9 hours of sleep every night, and younger people need even more than this. Ideally, this sleep should be uninterrupted and consistent. This means that you go to bed and wake up at the same time. Building good sleep habits, known as sleep hygiene, makes it easier to get the rest that you need so that your brain is primed for learning. Read more about how to set yourself up for better sleep in our list of 15 Tips to Improve Sleep Hygiene.

Right on Cue

Many of the most promising studies of hypnopaedia have been based on the idea of using special cues before, during, and after sleep. Associating a specific stimulus with a specific idea allows you to draw on that connection with hypnopaedia. Researchers have referred to this effect as Targeted Memory Reactivation (TMR).

In research studies, cues have been effective with both smells and sounds. For example, you could try sitting next to a fragrant plant like rosemary or lavender while studying a specific set of information. Then, you can use that same smell, in the form of a plant or essential oil, near your bed when you sleep. In the morning, take another whiff of that smell (in one of the prior forms or, for instance, with a scented soap or shampoo). This process may help your brain reflect on and process the associated information while you sleep, making it easier to recall it when you’re awake.

TMR can be set up with sounds as well by playing a specific sound during your learning and then repeating that sound during sleep. If you try sound-based TMR, some steps that may help make it successful include:

  • Using an easily recognizable sound such as that of an animal, mode of transportation, or musical instrument
  • Keeping the sound short, generally three seconds or less
  • Embedding that sound within background white noise during the night to reduce the risk of sleep disruption
  • Playing the sound consistently for a period after you have started to sleep soundly and as you are moving through the sleep cycle
  • Creating a custom recording that you can play using a stereo or mobile phone
  • Considering a nap since some studies have found TMR to be effective during a short afternoon nap. As a result, if you’re going to take a siesta, it may be worthwhile to play your sound cues during that time

Keep in mind that the setup of hypnopaedia experiments can be hard to replicate at home. In studies, researchers are present to monitor patients and play sounds, and just having a separate person to do this makes effective cueing much easier. In addition, conducting the experiments in sleep labs allows researchers to monitor a patient’s brain activity to know when they’re actually asleep and to optimize the timing of sounds.

It simply won’t be possible to self-administer sound-based TMR in your bedroom in the same way, so be patient and ready to do some trial-and-error to figure out what works best for you.

Put It on Repeat

There are some indications that repeated exposure to information that you’ve already learned can help you retain that knowledge. For example, you could play a recording of the language vocabulary words that you’ve recently studied or could play a melody of a song that you’re trying to learn.

Putting a recording of this information on repeat may be helpful, and as with TMR, may require creating a custom recording. You want the sounds to start after you’ve already started to sleep soundly, and you also want to make sure that the sounds won’t cause you to wake up in the night and have fragmented sleep.

Prime Your Brain Before Bed

If you want to improve the retention of something in your memory, you want to have that information be relatively fresh in your mind before going to bed. This doesn’t have to be immediately before going to sleep, though, as studies have found that reviewing information within the three hours before bed can improve memory consolidation.

Review When You Wake Up

If you’ve used any of these techniques to try to strengthen and consolidate memory while you’re sleeping, it may be beneficial to do another review when you wake up. It need not be an intense morning study session but rather just enough time for your brain to recall the information. If you used a TMR approach, you can again involve any established cues when doing your morning review.


What Are the Limits of Hypnopaedia?

While hypnopaedia offers intriguing potential benefits, it is important to understand its limitations, at least based on our present-day understanding. Some examples of the limits on hypnopaedia include:

  • It works with the information you’ve already learned: anyone hoping that they can put on a recording of another language and wake up fluent will be sorely disappointed. For TMR and other hypnopaedia strategies to work, it is almost always necessary to have already acquired the information.
  • It’s not made for multi-tasking: during sleep, the prefrontal cortex, the part of the brain most involved in executive function and task-switching, is less active. This makes it hard to use hypnopaedia to review multiple concepts.
  • It can be hard to carry out at home: implementing TMR and other methods of hypnopaedia is much easier for researchers in a controlled sleep lab. A home set-up may be impossible in some cases or may create disturbances for a partner who shares the same bedroom.
  • It may not help people who have underlying sleep problems: if your sleep is fragmented or disturbed because of a pre-existing sleep disorder like insomnia, obstructive sleep apnea, or Restless Leg Syndrome, you may not be able to take advantage of hypnopaedia.
  • It won’t work for everyone: even though hypnopaedia has had positive results reported in research studies, it’s important to remember that those results are an aggregate of data from all the study participants. Not everyone experiences the benefits of this approach, and it’s far from a foolproof method.

Over time, it’s possible that researchers will continue to reveal more about how to harness the power of hypnopaedia. This could include developing new techniques, devising ways to promote learning brand new information, or making it easier to follow hypnopaedia methods at home. As a result, our understanding of the benefits and limitations of hypnopaedia may very well change over time.

Are There Downsides to Hypnopaedia?

There are few concrete downsides to hypnopaedia, although there are some concerns. One potential problem is that hypnopaedia techniques may interfere with a person’s sleep and cause them to wake up in the night. Having a quiet bedroom environment makes it easier to fall asleep and stay asleep, and sound-based cueing with TMR may startle a person awake. To combat this, researchers have usually exposed a person to consistent white noise during the night to reduce the risk of a sudden disruption when the sound cues are played.

Another potential concern is that hypnopaedia could have unanticipated effects on overall learning or brain function. For instance, if the brain is normally reorganizing, purging, and processing information at night, it might be possible that hypnopaedia, when used over an extended period, could prevent the brain from carrying out those functions as it normally would. It is possible that this could tax the brain or affect the way the brain clears out toxins, manages long-term memory, or regulates key bodily systems, like the endocrine (hormone) and immune systems, during sleep. To date, long-term use of hypnopaedia has not been studied, so there is no evidence to state whether these are actual risks or if they are purely hypothetical.

A final concern about hypnopaedia comes from the field of ethics as concerns about manipulation or mind control during sleep trace back at least as far as Alduous Huxley’s novel  Brave New World. While this becomes more worrisome if and when hypnopaedia can implant totally new information, even certain types of contemporary TMR may create the potential for abuse in certain situations. The risk may be low, but from an ethicist’s perspective, it is important to consider in advance when and with which types of information hypnopaedia is morally appropriate.


What Are Future Directions in Hypnopaedia Research?

Hypnopaedia research has come a long way even in just the last decade. Researchers continue to unravel the mysteries of sleep and the brain, opening up the possibility that new advances will be made to boost sleep-based learning and instruction.

Obviously, an area of intense interest is in facilitating learning brand-new information during sleep. This type of hypnopaedia would unlock potentially enormous gains in knowledge without having to dedicate significant waking time studying.

Researchers are also investigating tools or software that could make it easier for people to take advantage of hypnopaedia. Wearable devices, like headbands, may also be invented to pulsate at specific times to increase slow-wave sleep and stimulate brain waves that can improve learning.

Health professionals are likely to look for other applications of hypnopaedia beyond retaining memories. For example, in the future, hypnopaedia may be a way of assisting people in rebuilding and retraining motor skills after injuries to the central nervous system.


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