Concur with Sleep paralysis (I believe it’s also called Isolated Sleep Paralysis). The general gist is you wake up (usually on your back) and the part of you brain during sleep that makes it so your body (typically) doesn’t knock things all around the room and act out your dreams when you sleep inhibits your movement, a side effect of this hormone also seems to be an uncanny feeling of complete, abject terror. It is oftentimes accompanied by a floating feeling, or pressure on your chest… as well as vivid hallucinations.
Many cases are what you describe, an old woman (often called the Old Hag) sitting on your chest. One common hallucination is the origin of “Nightmare” typically depicted as a sort of “hellhorse” either a horse with flaming hooves and mane, or a dark horse that is presided by an eerie fog or smoke.
It is often thought popular tales of the day inspire what you’ll see, or that these bouts of sleep paralysis fuel the legends, I’m guessing both. On a history channel show I saw, a very religious boy said he felt as if he were visited by demons. Something vaguely humanoid was behind his head “grasping” it with it’s long fingers. While small shadowy imp-like creatures danced around his room. He eventually began being “carried” down the hallway (and he actually saw the hallway), and ended up in his room somehow, in complete terror, but able to move again.
There’s some investigation into alien abduction being a sort of “advanced” sleep paralysis, all the symptoms are there, “floating” out your window, oddly shaped figures, feelings of terror. The “advanced” part comes in that you hallucinate to see a ship around you instead of just your house, but it’s not that hard of a leap (I mean the kid above thought he was moving throughout his house, that’s also a hallucination). You can see how these can perpetuate folk legends. The rumor mill spins out stories about aliens, people have vivid hallucinations involving being abducted, indistinguishable from reality, present these as fact (they don’t know any better), rumor mill picks up… makes more people have experiences, etc.
Apparently a good number of people (I believe 60%, but don’t quote me) experience some form of sleep paralysis once in their life, but whether they remember the experience or not is a different matter entirely. Only a handful of people (such as the boy above) experience it on a semi-regular basis though.
[QUOTE=aldiboronti]
The classic depiction is The Nightmare by Henry Fuseli.
Source
In Fuseli’s picture it’s an incubus on the victim’s chest. The equivalent female demon is a succubus. This would be ‘the woman with long black hair’ mentioned in the OP.
[/QUOTE]
Really? I always thought the Old Hag and the succubus/incubus were different hangups. Namely that the dream demons (succubus/incubus) were more sexually focused (i.e. they would try to kiss you or rape you).