Spooky footsteps, faint figures, the feeling of being watched — these unsettling signs of a ghost are as familiar to us as goose bumps on the back of our arm or neck.
Are there physiological explanations for those things that go bump in the night?
Absolutely, said Joe Nickell, a senior research fellow for the Committee for Skeptical Inquiry, an organization that promotes scientific inquiry and critical investigation of paranormal and other extraordinary claims.
“I’ve investigated haunted houses, inns, theaters, graveyards, lighthouses, castles, old jails, and even office buildings,” said Nickell, who’s researched stories of ghosts, vampires, werewolves, sea monsters, psychic phenomenon and other unusual phenomenon for 40 years. “And I’ve never found a paranormal explanation.”
“Ghosts” are often the result of pranks, environmental phenomenon, or physiological conditions such as sleep paralysis and the hypnogogic and hypnopompic hallucinations that accompany it, Nickell said.
Sleep paralysis occurs when there’s a disconnect between mind and body while people are going in or coming out of REM sleep, said Dr. Priyanka Yadav, a sleep specialist at the Somerset Medical Sleep for Life Center in Hillsborough, N.J.
“It can last from a few seconds to a minute or two and is often associated with hypnagogic hallucinations, things you might see when trying to fall asleep or hypnopompic hallucinations, things you see when you’re trying to wake up,” said Yadav.
These “waking dreams” can involve serpents, spiders, intruders, and yes, even ghosts and are often associated with feelings of dread.
“Some people have visions where they feel something is trying to strangle or choke them or they have a sense of impending doom,” said Yadav. “They’ll often see someone coming into their room and they’re not able to move or talk or scream or do anything.”
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The phenomenon, which has been suffered by humans for centuries, also explains both the demonic visitations people reported during the Middle Ages — as well as modern reports of alien abductions, said Nickell.
People who report hauntings will often experience them just as they go to bed or in the middle of the night.
“They’ll tell you they couldn’t move,” said Nickell. “That’s enough to diagnose it right there. It’s extremely common and very, very often the simplest and best explanation for a ghost.”
A ‘trick of the eye’
But it’s not the only explanation. Ghostly sightings can also be brought on as a result of a psychotic state, drug use, sleep deprivation or temporal lobe epilepsy. A “ghost” can also be an illusion produced by the brain, particularly when a person is tired.
“Someone will be doing some routine chore like polishing the furniture — they’ll be in a near-reverie or daydream state — and they’ll see something out of the corner of their eye,” said Nickell. “They’ll turn and their mind will fill in the blank — they’ll see a Civil War soldier or a ‘gray lady’ — and then it will promptly vanish.”
Studies have shown that people who are tired or are performing mindless tasks are more susceptible to these visions and, again, it’s a body thing, not a disembodied thing.
“It’s a trick of the eye,” said Nickell. “Your eyelid will twitch or an insect will fly by and this will trigger a momentary welling up of a mental image. It’s like a camera’s double exposure for just a brief moment.”
Carbon monoxide poisoning — and the hallucinations that can occur with it — is another possible explanation.
In 1921, the American Journal of Ophthalmology published a case study involving a couple who moved into a house and promptly began to suffer headaches, listlessness and strange auditory and visual hallucinations: footsteps, mysterious figures and strange sensations. Their symptoms were finally traced to a faulty furnace.
More recently, in 2005 a woman was found delirious and hyperventilating after seeing a “ghost” while taking a shower. It was discovered that a new gas water heater had been improperly installed, flooding her house with carbon monoxide.
Other environmental explanations for ghostly phenomenon include:
- Low-frequency sound waves (infrasound), said to cause feelings of nervousness and discomfort and vibrations in the eye which can produce illusions.
- Fluctuations in the electromagnetic field, which can purportedly interact with the brain, causing dizziness, hallucinations.
- Other neurological symptoms. Paranormal buffs often point to these fluctuations as proof of a ghost’s existence.
- Inconsistent lighting and temperature, which in certain circumstances can unconsciously “spook” human beings.
Can a person build their own “haunted” house by incorporating these elements?
In a May 2009 paper in the journal Cortex, psychologists from Goldsmiths College in London wrote about their attempt to do just that. They asked 79 participants to spend 50 minutes inside their “haunted” chamber.
No one died or was driven hopelessly insane, although “many participants reported anomalous sensations of various kinds.” The researchers attributed it not so much to the experimental conditions but to one other common explanation for ghostly experiences: “suggestibility.”
This spooky story was originally published in 2009