Al Cheyne, a retired professor of psychology at the University of Toronto and the University of Waterloo has been researching sleep paralysis for 10 years.
"It's a dream hallucination," Cheyne
said."It's an intrusion of dream-like imagery into your waking life.That's why it tends to occur around times of falling asleep or waking up and waking up in the middle of the night in this state where you can't move."
People report a sense of something or someone in the room, and a sense of terror is common, he
Some people will wake up and not be able to move for a few seconds, he
"For others, more elaborate types of hallucinations happen," he
said."Some are extraordinarily elaborate like full-fledged dreams.For others there's a sense of something there."
Sleep paralysis happens most often in the bedroom because that's where people do the majority of their sleeping, Cheyne
"But people have reported it happening to them in libraries when they've dozed off, or in their cars when they've pulled over on the side of the road for a rest," he
said."It can happen in various situations when people are tired.It's usually when they're about to fall asleep or just waking up."
Some can have a once-in-a-lifetime brief episode or it can be an elaborate experience, he
has a website (http://watarts.uwaterloo.ca/~acheyne/) where people can get information about sleep paralysis and are also invited to e-mail him with their experiences.He
has collected more than 28,000 tales of sleep paralysis from all over the world. SEVERAL TIMES
"In my sample I have a large number of people who have it quite regularly night after night for weeks on end," he
research has led to three types of sleep paralysis: the intruder, the incubus and bodily experiences.
"It feels like you're floating off the bed," Cheyne
said."You might even feel like you're leaving your body so it's an out-of-body experience." Cheyne
recalls a case in which a woman thought she
had come out of a dream and tried to turn on the light switch and found it wouldn't work.
"Suddenly they find themselves back in bed," he
said."This can repeat itself several times.It's called a false awakening."
Although the out-of-body experience can be quite disturbing, Cheyne
said people are attracted to idea of floating and flying out of the room or over houses.
"Some people who experience sleep paralysis associate it to astral travel, which is the belief that people leave their bodies during the night to visit friends," he
said."Some might contact me asking how they might produce these experiences."
But, most people who contact Cheyne
ask him how to make episodes of sleep paralysis stop.
"I offer advice on how to cope and possibly prevent them," he
said."For many people it's simply avoiding lying on their backs when they're falling asleep because that's the most common position." He
said some people will have the experiences no matter how they're lying.
"For a lot of people it exclusively happens when they're lying on their backs," he
said."I have no idea why that is.It's one of the most intriguing things about it.We have ideas and theories of why, but nothing particularly convincing." Cheyne
stumbled into his
sleep paralysis research project when talking with a university student who was writing an article on alien abductions.
was trying to come up with some psychological explanations for why people thought they were being abducted by extraterrestrial aliens," he
said descriptions of people's so-called abductions sounded a lot like sleep paralysis.
Thoughts on dreams or hallucinations depend on how they are interpreted.
"People have different kinds of world views," he
was told vivid details of a man's experience with aliens he
encountered during sleep paralysis.
"The man woke up paralyzed and felt himself floating and being levitated up to some sort of space ship," Cheyne
recounted."There were alien creatures that came in and did various kinds of experiments on him.He
described all the feelings of pain very vividly.He
was quite adamant throughout his
recollection that he
didn't believe it for a moment.He
had a most elaborate kind of experience and he
didn't know what it was when it happening, but he
was convinced it must have been some kind of dream or hallucination." Cheyne
said other people who share their stories with him had nothing more than a brief period of paralysis and they're convinced they were abducted by aliens.
"It's interesting that some people would take almost nothing and give it a very vivid and what most people would think is very far-fetched interpretation," he
said."Other people can have the most vivid, compelling kinds of experiences and just think it's a bit weird and that's the end of it for them."
It's the diversity in people's reactions to sleep paralysis that interests Cheyne
"What people do with those experiences depends a lot on their belief systems and also the culture that they live," he
said, adding personality characteristics play a part as well.
A fantasy-prone personality, which is related to the ease a person can be hypnotized, has a direct affect on how they interpret their experience.
"I've looked most at a fantasy-prone personality," he
"They might think it's a stroke, a neurological disorder and maybe they're going crazy," Cheyne
Over time people have reported that their hallucinations can become less, Cheyne
"Some say even after seeing his
website and reading about it the experience becomes less vivid," he
The majority of emails he
receives are from people who are grateful that he's
doing the research and has put up a web page, he
"They've been suffering from this for years and years and have not told anyone or maybe they did and the person thought it was very weird it didn't happen to them and it was very strange so they shut up about it," he
said."People will often say they've got tears in their eyes when they're writing me because they've had this horrible experience for years and years and had no idea what was happening to them," he
Most people who find his
website find it reassuring that they're not the only one, he
"It's remarkable how often people will say that," Cheyne