Your mommy and daddy might have told you there are no such things as ghosts.

But nearly half the country thinks otherwise.

A HuffPost/YouGov poll shows that 45 percent of Americans believe in ghosts, or that the spirits of dead people can come back in certain places and situations.

The idea of ghosts as hopeful evidence of life after death goes all the way back to ancient Egypt, where it was commonly believed that death was merely a transition to some mysterious netherworld of another existence.

While skeptics deny the existence of ghosts, claiming there's no real evidence, polls and surveys have shown the public strongly disagrees.

Of the 1,000 adults interviewed Dec. 17-18, the HuffPost/YouGov poll revealed 45 percent believe in ghosts, or that the spirits of dead people can come back in certain places and situations. When asked if they believe there's a life after death, 64 percent responded Yes. While 59 percent of adults don't believe they've ever actually seen a ghost, 43 percent also don't think that ghosts or spirits can harm or interact with living people.

Check out these ghost images through the years

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  • Ghost Dog At A Tea Party

    In 1916, retired Scotland Yard Inspector Arthur Springer took this picture in Tingewick, Buckingham, England. At the moment he captured the photograph, there was reportedly no dog in the frame at all.

  • Raynham Brown Lady

    One of the most famous ghost images ever taken, this is allegedly the ghost of Lady Dorothy Townshend, who lived in Raynham Hall in Norfolk, England during the 1700s. After her death, Townshend’s spirit was reportedly seen many times, and in 1936, a photograph of the interior of Raynham Hall revealed the ghostly form of a woman descending the stairs.

  • Graveyard Child Ghost

    In the mid-1940s, a Mrs. Andrews of Queensland, Australia, photographed the grave of her daughter, Joyce. When the film was developed, a small child appeared in the picture. Years later, two graves of young infant girls were found near Joyce’s grave.

  • Church Ghost

    In the early 1960s, the Rev. K.F. Lord photographed the interior of his church in Newby, North Yorkshire, U.K.. When the film was developed, a translucent hooded figure appeared to be standing to the right of the altar. See next slide for a close-up of the figure.

  • Church Ghost Enlarged

    This is an enlargement of the Newby, U.K. church ghost from the previous slide.

  • Printers Alley, Nashville, Ghosts

    This recent image, taken by Bret and Gina Oldham, shows two ghostly figures in an area of Nashville known as Printers Alley. In the foreground is a figure of a large woman in a long dress and her hair pulled back. And in front of this "spirit," the figure of a man appears to be standing against a building wall.

  • New Jersey Library Ghost

    Image photographed in 2011 by Frank Lazzaro of a strange figure peering through a doorway of the Old Bernardsville Library in New Jersey.

The results aren't far off from previous polls, including a CBS News 2009 study, which showed that "nearly half of Americans say they believe in ghosts, or that the dead can return in certain places and situations." That poll also revealed that 78 percent of Americans believe in life after death.

"After more than 60 years researching the paranormal, and nearly that many investigating haunted houses, I spend little time these days theorizing about what ghosts might be. I completely accept the existence of such phenomena," said Brad Steiger, author of "Real Ghosts, Restless Spirits and Haunted Places."

Steiger told The Huffington Post about a close encounter he had with a possible ghost. It was in the 1960s and he was with a skeptical police officer at a mansion in Iowa.

"This apparition first appeared in the stables, then it would walk across the lawn of the estate and enter the house. When it began to materialize, [the officer] said, 'What is that?' And I couldn't resist. I said, 'I don't see anything,' and the guy was actually reaching for his service revolver, to shoot at it. That's when I said, 'No, that's what we're here investigating. These things are real.' "

Steiger recalled the strange figure was about the height of a 5-foot, 11-inch man.

"It began first as sparkling lights swirling around, and then it solidly materialized into a hazy form of a man. To me, it was like seeing someone through a fog -- you could distinguish features. It was very dramatic."

Check out these ghostly images from around the world

Henry Bailey, an aerospace engineer, has investigated ghosts and paranormal subjects for 50 years. He told HuffPost of his encounter with a spirit in Germany in the early 1970s, when he was staying in an apartment above a local tavern.

"The room that I was in got extremely cold and it bothered me a great deal, and I woke up and looked at the bedroom door -- which I had left open and was now closed -- and leaning against the door was an apparition of a gentleman, in old German-European attire, propped up against the door," Bailey said.

"I just kind of shook my head and said, 'No, that can't be,' and I turned back around and it was still there and then the third time, he was gone.

"Now, I had no idea that this apartment was haunted, and [my friend] said he was staying out of the apartment for more than one reason -- the cabinets would open and the wine glasses would move from the cabinets to the table. What I learned after seeing this ghost was that one of the prior tenants -- a man -- was found dead, propped up against the bedroom door, and it was exactly what I had seen."

While Bailey said he believes enough anecdotal evidence points to the possibility of life after death, he's not optimistic that the whole world will finally accept this.

"Will there ever be any objective proof in my lifetime about paranormal phenomena or ghosts? Highly doubtful. You've got a better case for UFOs."

The idea of disembodied spirits can have a strong psychological hold on individuals.

"I think that people believe in ghosts or spirits because it provides comfort. There are so many things in life that are hard to explain, and that's why we tell stories and have myths," said New York City-based psychotherapist Jonathan Alpert.

"It can be inspiring for people who feel uncertainty, and this isn't too different from [the recent fears] about the world ending," Alpert told HuffPost. "When there's uncertainty, the brain craves information, to help calm down certain fears. If we're afraid of death or what happens after we die, we might create these stories or ideas about if there's an afterlife or ghosts. So, I think it helps to calm down people's fears and anxieties."

Even after so many years of personal investigation and reported close encounters, Steiger said he isn't surprised, with all of the available technology -- like paranormal phone apps that supposedly aid in detecting ghosts -- that there's a lot of doubt about the existence of ghosts.

"There are still many hardcore scientists who regard it as superstition and a residual fear of our past," said Steiger. "I put ghosts in what I call a psychic residue category. I think this explains the vast majority of hauntings where you cannot interact with the ghost any more than you can interact with the figures on a movie or television screen.

"In environments where human drama has taken place -- a murder, death, someone dying in pain, suffering -- those last moments of emotional energy are somehow impressed in the environment. Very rarely do you hear about a happy ghost."

Alpert suggested that a belief in ghosts may be potentially harmful. "It could be. I think if people are avoiding certain situations or are reckless in their lives because they think there's an afterlife and they can take such risks, that could be a problem," he said.

"But whether [it was] the world ending on December 21st or ghosts, any activity like that -- if it's taking over your life, occupying so much of your time, and if you're becoming obsessed with it, then it's certainly a problem."

The HuffPost/YouGov poll was conducted Dec. 17-18 among 1,000 U.S. adults. The poll used a sample selected from YouGov's opt-in online panel to match the demographics and other characteristics of the adult U.S. population. Factors considered include age, race, gender, education, employment, income, marital status, number of children, voter registration, time and location of Internet access, interest in politics, religion and church attendance.

The Huffington Post has teamed up with YouGov to conduct daily opinion polls. You can learn more about this project and take part in YouGov's nationally representative opinion polling.