Hypnagogia comes from the Greek words for “sleep” and “guide,” describing the transition period between wakefulness and sleep. Many people experience hallucinations as they fall asleep which may give them creative insights, leading artists like Salvador Dali to nickname it “the slumber with a key.”

Have you ever experienced hypnagogia? What causes these hallucinations? Keep reading to learn more about hypnagogia, its relation to REM sleep, and how to induce it.

What is hypnagogia?
Hypnagogia is the dream-like state that occurs in the transition between wakefulness and sleep. It usually lasts a few minutes at most and occurs as the individual is falling asleep (as opposed to hypnopompia, which occurs as the individual is waking up and is less common). Many people with hypnagogia experience visual or auditory hallucinations or disturbances, or a feeling of falling or floating.

In hypnagogia, both alpha and theta brain waves are present. Typically these brain waves present separately, during waking or sleeping states, respectively, but their coexistence during hypnagogia may account for the bizarre imagery and auditory experience. Auditory hallucinations may include random words, noises, music, or phrases. Visual hallucinations may include random images, phosphenes, or the Tetris Effect.

Phosphenes are tiny specks the brain interprets as lines and geometrical patterns during the hypnagogic state. This abstract imagery can also occur when an individual has experienced sensory deprivation and the brain goes into overdrive trying to recreate it.

The Tetris Effect
The Tetris Effect is one such interesting visual experience that can occur during hypnagogia. You dream yourself reporting a repetitive task from your daily life, much like the repetitive falling of the blocks in a game of Tetris. During sleep, your mind processes cognitive information from your day and consolidates memories. Experts assume the Tetris Effect is a visual representation of your brain cementing these new tasks and learnings.

How common is hypnagogia?
Hypnagogia is fairly common, although many individuals don’t even realize they’ve experienced it. For comparison, only about 5 percent of people experience hallucinations when they’re fully awake, but sleep hallucinations affect between one-fourth and one-third of people.

Hypnagogic hallucinations are more common in adolescents and slightly more common in women. Hypnagogia is also more common with sleep disorders like narcolepsy and insomnia, shift work sleep disorder (from the havoc it wreaks on the body’s natural circadian rhythms) and mental illnesses like schizophrenia.

Is hypnagogia dangerous?
There is a difference between the harmlessness of hypnagogia and the more serious hallucinations characteristics of narcolepsy. Overly vivid or disturbing imagery could be indicative of narcolepsy or another sleep disorder. This is especially true if the hypnagogic hallucinations or sleep paralysis occur during the daytime. These hallucinations cause the individual to see things that are not there, due to the brain not fully catching up to wakefulness.

Hypnagogia vs REM dreams
Hypnagogic imagery often seems random and disconnected, which is what differentiates it from “normal” dreams. Normal dreams occur during the REM part of the sleep cycle and are more likely to follow a narrative structure.

In 2013, researchers documented the differences in perceived activity during REM dreams and hypnagogia. REM dreams feel more “real,” in that an individual perceives themselves to be walking through and actively engaging in the dream environment. Hypnagogia, on the other hand, is more of a passive experience where the person feels like an observer.

Hypnagogia and creativity
During hypnagogia, the brain is more fluid and open to making connections between seemingly unrelated ideas, which is what makes it so conducive to creative problem-solving. While the field of research is still young, multiple studies have established a link between dreams and improved creativity and problem-solving.

Anecdotally, some artists and inventors have attributed hypnagogia for helping them create their greatest work. Inventor Thomas Edison and surrealist artist Salvador Dali often induced hypnagogia using a similar technique. Both men held something metal in their hands while they fell asleep. As their hand relaxed, the item would clang onto the floor and wake them up.

How to induce hypnagogia
Because of its associations with enhanced creativity, many people wish to induce a hypnagogic state. These techniques are not necessarily backed by research but may prove helpful nonetheless.

Before you fall asleep, think about the problem you are trying to solve or the creative project you are working on. Consuming your thoughts with information about the subject may make you more likely to dream about it.
Copy the technique used by Salvador Dali and Thomas Edison. Hold something in your hand that will make a noise when it hits the floor. As you drift off to sleep, your hand will relax and the object will bang against the floor. Keep repeating this exercise until you start to enter a hypnagogic state.
Keep a notebook by you, so when you wake up you can immediately jot down ideas or sensations from your dream. Alternately, there are many lucid dreaming and dream journal smartphone apps that help you enter a hypnagogic state and provide audio and text recording capabilities for you to capture your notes.