What Is Hypnagogia?

Hypnagogia describes that magical state just before you fall asleep. At this point you are not yet dreaming or completely unconscious, and yet you will often notice your thoughts start to drift as you slowly lose your grip on reality – as though your mind were ‘leading’ you in to sleep. In fact the term hypnagogia actually means ‘leading to sleep’ (hypnos meaning sleep – which is also the route of words like hypnosis). While the term is generally used to describe the moments before sleep however, it can also refer to the moments immediately following sleep as you come around from a dream and don’t quite yet have command of your full faculties.

During this state, it’s possible to note a range of interesting phenomena that give us some insight into the workings of the brain and of our body’s sleep/wake cycle. Here we will look at a couple of those.

The Tetris Effect

One interesting effect that can take place is called the ‘Tetris effect’. Named after the popular computer game, the Tetris effect is what happens when you close your eyes and ‘see’ yourself performing a repetitive task from your day in your mind’s eye. For instance, if you were to play the game Tetris long enough, then you might find that you see Tetris pieces falling in front of your eyes as you start to fall asleep.

The reason for this is that you will have formed new neuronal connections in your brain by repeating those repetitive tasks. This then causes them to fire and strengthen as you fall asleep, and from an evolutionary perspective this is what helps us to further cement abilities that we have learned during the day in order to improve our performance when we return to them.


One of the best documented aspects of hypnagogia is the presence of ‘phosphenes’. These are tiny speckles that we see as lines and random geometrical patterns. Ultimately we may start to interpret these as images, and it may be that it is in eventually giving these images narrative content that we ultimately form the experience of dreams as we know them. The transition may be phosphenes > fragmentary dreams > dreams.

These phosphenes in turn may be caused by a lack of visual stimulus that causes the brain to become oversensitive to visual stimuli and eventually end up ‘creating’ its own. A similar effect can be triggered through sensory deprivation.

Auditory Hallucinations

Less common are auditory hallucinations, though they can also occur during this stage. These can be faint, or loud enough to jolt you awake. Often they will include word play and made up words and names. Sometimes music will be heard (especially on waking) and sometimes the sound may manifest form the individual’s own ‘inner voice’. Again the cause is likely auditory deprivation leading to the ‘invention’ of sound by the brain. It would be interesting to see in a study whether a quieter environment could lead to a greater incidence of auditory hallucinations during hypnagogia.

Sleep Paralysis

One rare but rather disturbing experience that can occur during hypnagogia is sleep paralysis. Sleep paralysis is when the subject is awake, but cannot move, and may still continue to experience dream like hallucinations and feelings.

This occurs due to something called ‘REM atonia’ – which is the normal paralysis we experience during sleep that prevents us from acting out our dreams. In sleep paralysis, the atonia simply persists after the individual has woken up, or occurs before they have fallen asleep. Sometimes the experience will be joined by rushing noises in the ear, intense emotions, or the feeling of ‘other presence’ in the room. It has been suggested as a potential explanation for many reports of alien abductions and hauntings.

Threshold Consciousness

Threshold consciousness more precisely describes the state of our consciousness prior to sleep, and the thought processes that we experience in this state are of particular interest to researchers.

Generally, as we get closer to sleep, we will often find our thoughts change as we lose some of our ‘ego boundaries’ (our sense of self) leaving us to feel more open, sensitive and empathic. Meanwhile we find ourselves losing some of our logic as our thoughts become non-sequential and we might also find ourselves more suggestible to outside noises and influences (external stimuli are readily incorporated into our narrative and EEG recordings show increased responsiveness to external sounds at this time). Fluid association can occur between ideas without the usual restrictions leading to seeming random trains of thought, which occasionally can yield useful insight. Famously, August Kekulé reports realizing the structure of benzene was a closed ring while in a hypnagogic state. Many other writers and scientists also report similar experiences – which is likely the result of a combination free association and the Tetris effect. A study conducted by psychologist Deirdre Barrett shows that hypnagogia is actually more useful for problem solving than full-blown sleep.

The cause of these unusual thought processes is likely due to the shutting down of brain areas. As we rest, we stop using some of the portions of our brain responsible for particular roles. Our concept of ‘self’ for instance is closely tied to particular brain areas – when this closes down we can start to ‘lose’ that sense of self (this also occurs in drug use and during meditation).

So the hypnagogic state is not as mysterious as it may at first seem, and we can explain most of the phenomena that occur. However that makes it no less fascinating an insight into the workings of our own minds, and no less useful as a tool for introspection.

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