Ask a professor why people think "paranormal activity" really exists, you'll get one answer. Ask a psychic who de-haunts houses, you'll get another.
The found-footage "Paranormal Activity" horror movies—the third installment, a prequel, opened on Friday—are popular not just because people like to be scared, academics who have researched the field say, but because belief in supernatural forces is deep-rooted in all cultures.
Carson Mencken, professor of sociology at Baylor University in Texas, who co-authored the book "Paranormal America," did his research by meeting people across the country who spend their weekends at ghost hunts, psychic fairs, Bigfoot hunts or UFO searches.
"People are looking for enlightenment and they're looking for discovery," Mencken said. "There are hard-core committed believers. For other people it's just a cool thing to do." The enthusiasts are not crackpots, he said. "They are people who come from all professional walks of life."
"Paranormal beliefs are for the most part substitutes for religious beliefs," said Michael Persinger, professor of neuroscience at Laurentian University in Ontario, Canada. "People have to believe in something—it's either one or the other."
The most common paranormal experience, he said, is the feeling of a sensed presence—which people may call a ghost, an alien, or a spirit.
The reality of those ghosts is uncontestable to Lorraine Warren and her son-in-law Tony Spera, who run the New England Society of Psychic Research, started by Warren and her late husband Ed. "We don't have to prove to you that ghosts exist," said Spira, 60. "Do you believe in God? He created spirits and there are spirits among us."
He and Warren, 84, help terrified people who believe their houses are haunted.
"People say, 'There's a shadow walking by me, or 'I hear footsteps and there's no one home,'" said Spera. "They may hear people talking in another room or behind a wall." They may smell a whiff of perfume of a loved one who's deceased.
They quiz the people who contact them to make sure they're not on medication, abusing alcohol or drugs.
If they think the callers are legitimate, Spira said, they will usually suggest having the house blessed by a member of the clergy.
"A lot of the big religions have the rite of exorcism within their teachings. It often works," he said.
If that doesn't help, he and Warren pay a house call. "Lorraine is a clairvoyant, she's a psychic too. As soon as she comes into a house, she would know," Spira said. "She can tell if that entity is a human spirit or from another world."
"When I go into a house where there's infestation taking place, I discern," says Warren.
She recalled a visit to a home in New York State last week where the owner was hearing knockings.
They sat at the dining room table near a big cabinet.
"It was as if somebody took their fist and hit it very hard," she said of the sounds she heard. Things have been peaceful for the last couple of nights since her investigation, she added.
On a trip to England, she said, she visited Borley church in Essex, famous for its White Lady ghost.
"I could feel the energy and I could see this beam of light go right across. It was beautiful to see the spirit of this woman."
Stewart Guthrie, professor emeritus of anthropology at Fordham University, has studied such phenomena.
"What is a ghost? A ghost is the disembodied spirit of a deceased person," he said. "Why do we see them? We see them because .. the world is infinitely complex and our means of understanding it are limited. It's a good bet to assume there is something there, some sort of agent, when there's a thud in the night."
"Everybody in every culture has a default label for the unknown," said Persinger.