9/101 The Sandman: Hypnagogic Hallucinations

Green, grey, blue and purple paisley pattern of repeating leaf-like shapes


You, some darkness, and a bed.


The Sandman, as you know, is a mythical being who come to you at bedtime and throws a little light dust in your eyes, to make your eyelids heavy and full of sleep.

When I was young (pre-teens and early teens) I used to see visions as I lay on the cusp between wakefulness and sleep. Behind closed eyes I saw a whole series of phantasmagorical hallucinations, every night.

These would usually consist of vividly coloured patterns of repeating motifs. I had considerable control over them; I could wait for a shape such as a square to spontaneously materialize out of the void, and then I could will it to grow or shrink, and to reduplicate itself at regular intervals, so it became like a frieze or a wallpaper; and to change its colour, and even move or pulsate. Sometimes I could even decide what I wanted to see and it would appear as though magicked into being. All the visions were of great beauty and I could (and did) prolong them for a long while until sleep overtook me. I always found them friendly and benevolent.

Often the motifs were geometrical, so what I saw was like tiling, but the most frequent illusion was a Paisley pattern like the one above.

I never told anyone else about this at the time (and in fact not until now). Neither adults or my contemporaries ever described anything like it and I never read or heard anything to suggest that other people might have similar experiences. I assumed I was alone in seeing what I saw and people would not understand and just laugh if I mentioned the matter. They would have said I was ‘imagining things’. (Which I was of course.)

As I grew up I seem to forget about these visions and now I don’t see them anymore.

Many years later I was to discover that these are called hypnagogic hallucinations and that at least half of us see them.

Oliver Sacks devotes a chapter to them in his fascinating book Hallucinations. Because people fear reporting to others that they have seen any kind of hallucination these phenomena go under-reported and only careful modern studies reveal just how common they are.

For all I know you may see these vision regularly. If so the experiment may not interest you so much, but I’d be extremely interested to hear what you see.


Close your eyes tightly, put your hands over your eyes for greater darkness, and concentrate hard on what you see. It’s probably like looking at a swarm of little insects of light. These are phosphenes – the sensation of light without light being present. It’s possible you may see more elaborate patterns or shapes, and even faces. If you see only the random phosphenes then wait until bedtime and try the experiment again. Be prepared to try on two or three successive nights: I think there may be an ability that comes with practice and I lost it through lack of practice.


The hypnagogic hallucinations I remember were similar in many ways to the hallucinations I experienced when I had Charles Bonnet Syndrome (CBS). I saw many of the same shapes and patterns. So we might speculate that in both cases neurons deprived of visual input are constructing random images, but the neurons concerned are specialized for seeing shapes, patterns, faces etc. (we know such neurons exist).

One notable difference, for me, is that I could have an element of control over the hypnagogic illusions – I could manipulate and change them, and even conjure them up, although I believe all this is unusual and most people just witness hypnagogic hallucinations.

However I had little or no control over the hallucinations caused by CBS. I read that they can sometimes be driven off by staring directly at them (which has a kind of intuitive appeal), and that seemed to work for me on occasion. But I never heard of anyone being able to do the opposite and summon or modify CBS hallucinations.

It’s interesting to note that – rather like migraine aura, thought to have been the source of visions of St Hildegard of Bingen – hypnagogic visions seem to have influenced Swedenborg, another impressive religious mystic.

I believe these mystical experiences are at bottom only neurological, but understand very well why people can be profoundly affected by them.

Next experiment

The next in the series, 10/101 will be ‘The Scrying Glass”.


Paisley pattern: http://commons.m.wikimedia.org/wiki/File:Paisleymuster1.jpg



About partialinsight

One evening I had a stroke. Half my sight vanished overnight. Adapting made me grasp how amazing the visual system and brain are. It also taught me to understand disability completely differently and I'm grateful for the lesson.
This entry was posted in 101 experiments in seeing, Art and vision, The brain and visual perception and tagged , , , , , , , , , , . Bookmark the permalink.

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