© Shutterstock

Paranormal beliefs - A study found that about three in four Americans have at least one paranormal belief.

© iStock

Survey - A survey commissioned by Grupon in October 2018 found that over 60% of the people surveyed have seen a ghost.

© Shutterstock

Power of suggestion -

Some people believe they see ghosts because they’re expecting to see ghosts. If they’re told that they’re in a haunted house, they’re much more susceptible to a paranormal experience.  

© Shutterstock

Power of suggestion - A study conducted in 1997 put 22 people in a creepy theater. Half of the people were told that the place was haunted, and the other half was told the place was under construction. Can you guess which half saw or sensed something paranormal?

© Shutterstock

Power of suggestion - Half of these people were led to believe that something otherworldly might happen, so the group that was told they were in a haunted theater experienced it.

© Shutterstock

Brain problem - It's possible that some of the people who see ghosts have a brain malfunction. While investigating a woman’s epileptic seizures, a neurologist found that applying current to a certain part of her brain made her feel like there was a presence behind her, mimicking her.

© Shutterstock

The God Helmet - Originally called the "Koren Helmet," it's a device that sends magnetic signals to one's brain. Built to study religious and mystical experiences, it can apparently trigger paranormal experiences.

© Shutterstock

The God Helmet - Supposedly, some people claimed to have had visions of God during the experiment, while others felt a presence, among other paranormal experiences.

© Shutterstock

Stress - A study concluded that stress can cause women to report paranormal experiences. Traumatic stress was linked to experiences such as possession and extra-sensory perception.

© Shutterstock

Frequencies -

Maybe ghosts are just really low sound frequencies. More specifically, infrasounds, which are sounds below the normal range humans can hear.

© Shutterstock

Infrasounds -

These frequencies can actually trigger physical and emotional responses akin to paranormal experiences.

© Shutterstock

Mold - What is a haunted spooky place without a bit of mold, right? Well, the truth is that certain types of mold can actually make you hallucinate, and affect balance and coordination.

© Shutterstock

Coping mechanism - People who've lost loved ones have reported being visited by them. The ghostly visits could be a coping mechanism used by the grieving brain.

© Shutterstock

Maybe it’s just a draft - Cold spots in a house, for instance, are believed to be a sign of paranormal activity. But a sudden change in temperature in a specific spot doesn’t necessarily mean you’ve encountered a ghost.

© Shutterstock

Maybe it’s just a draft - Changes in humidity levels, a drafty window, or a chimney might be responsible for the cold sensation at a specific spot.

© Shutterstock

Maybe it’s just a draft - A study found that ghostly activity was more consistently reported in known "haunted" locations. But environmental factors such as magnetic fields and lighting levels could be to blame.

© Shutterstock

Carbon monoxide poisoning - In the 1920s, the Journal of Ophthalmology documented a case study about a couple who reported paranormal experiences at home.

© Shutterstock

Carbon monoxide poisoning - It turns out that they were in fact having hallucinations, triggered by a CO leak in the furnace.

© Shutterstock

Exploding head syndrome - Exploding head syndrome happens when you experience a loud noise, usually when falling asleep or waking up. It’s like a phantom loud explosion.

© Shutterstock

Exploding head syndrome - This likely happens because the part of your brain responsible for shutting down your body to put you into a sleep state gets a bit confused, and does the opposite instead, putting you in a state of alert.

© Shutterstock

Exploding head syndrome - So that loud explosion you heard was not a ghost trying to blow up your house, but actually your brain being a bit out of sync.

© Shutterstock

Sleep paralysis - Paranormal experiences are common during sleep paralysis. This phenomenon occurs when you’re in a dream state, but you're half-awake and unable to move. This is usually a confusing and sometimes terrifying experience.

© Shutterstock

Sleep paralysis - Paranormal experiences are sometimes reported during this state of semi-consciousness. But the truth is, you’re likely dreaming.

© Shutterstock

Orbs - Those little balls of light that so many people claim to be spirits, can actually be explained by science.

© Shutterstock

Orb photography - If not photographic evidence of spirits, what are these orbs then? Well, they can be a number of things, including dust, pollen, insects, moisture, or even just a dirty camera lens.

© Shutterstock

Sometimes, we just want to believe -

Believing in ghosts does help us cope with our own mortality, and like any other belief system, helps us make sense of our place in the world.

© Shutterstock

Did you know - That these celebrities also had paranormal experiences?

© Shutterstock