Why do we have the same nightmare of a ghostly intruder?

The Hat Man is usually tall. He wears a broad-brimmed hat and a trench coat. And people  across the world have reported sleeping encounters with him.

For about as long as we’ve had records, people have described a terrifying nightmare vision that paralyzes them with fear and a crushing feeling on their chest.

Recently, the Hat Man has been making night calls. In the past, it’s been an old hag, a witch, or souls of unbaptized babies who come to strangle victims in their sleep.

A recent article by Quartz describes the terror the Hat Man instills:

“The shape of the frightening figure occasionally varies, but the way he makes his victims feel never does: utterly paralyzed with terror, and breathless, as if fear had frozen them from the inside out.”

Compare this to an account by 17th century Dutch physician Isbrand Van Diembroeck:

“[W]hen she was composing her self to sleep…sometimes she believed the devil lay upon her and held her down, sometimes that she was [choked] by a great dog or thief lying upon her breast, so that she could hardly speak or [breathe], and when she endeavored to throw off the [burden], she was not able to stir her members.”

By the late 20th century, science offered a new explanation: Sleep Paralysis.

Imagine being conscious but unable to move. It’s possible that our brain paralyses our body to ensure we don’t act out intense REM dreams.

But we start to wake up mentally..

During this transition between stages of wakefulness and sleep, you may be unable to move or speak for a few seconds up to a few minutes. Some people also feel pressure or a sense of choking.

This hybrid state is often accompanied by hallucinations, the most common of which being a sensed presence. 

Stress, caffeine, and sleep deprivation can all make these episodes more frequent and intense.


The ‘mare’ of the word ‘nightmare’ is derived from the Norse word ‘mara’. This refers to a supernatural – usually female – being that lies on people’s chests at night suffocating them.

By 1500, at least in Europe, this sleep paralysis was frequently interpreted as witch attacks.

Writing in 2003, Davies quotes examples of sleep paralysis found in evidence used at the Salem Witch Trials of 1692. Accused witch Susan Martin had reportedly told Robert Downer that “some She-Devil would shortly fetch him away”. That night, Downer claimed

“as he lay in his bed, there came in at the window, the likeness of a cat, which flew upon him, took fast hold of his throat, lay on him a considerable while, and almost killed him.”

Another accuser, Bernard Peach, gave ‘evidence’, testifying that “he heard a scrabbling at the window, whereat he then saw Susanna Martin come in, and jump down upon the floor. She took hold of this deponent’s feet, and drawing his body up into an heap, she lay upon him near two hours; in all which time he could neither speak nor stir.” When the paralysis began to wear off he bit Martin’s fingers and she “went from the chamber, down the stairs, out at the door.”


In the Middle Ages this type of nightmare was so common that had it a name: incubus (‘the crusher’ in Latin).

The medieval medical writers all note that the patients believe that some sort of creature was attacking them at night. Bernard de Gordon notes that “the common people say that it is little old woman stomping and pressing on their bodies”.

Medieval doctors offer various explanations on what can trigger incubus : one blamed eating raw foods before going to sleep. Others found that the position of the sleeper, how warm the bedroom was, or even a superfluity of phlegm could result in incubus. Many writers connected it with epilepsy, and even find it to be a minor form of that disease.

The medieval solution? Avoid stress.

Bernard de Gordon states that “he should live in joy and happiness and avoid all sadness,” and suggests making the patient feel better by having music played or conversations with friends.

Hat Man

Christopher French, a psychology professor at Goldsmiths, University of London, thinks there’s a connection between Freddy Kruger and the Hat Man. We interpret our nightmares depending on our cultural norms.

In Medieval times, an evil spirit sitting on your chest was the most obvious explanation. To people interested in aliens, alien encounters make sense of a terrifying experience.

Whatever you do… DON’T… FALL… ASLEEP…

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