If you believe in ghosts, you are far from alone. Around 45% of Americans believe in ghosts and as many as 18% of people will go so far as to say they have had contact with a ghost. I will also admit to spooking myself out on occasion when my dog has refused to stop barking at what appears to be an empty corner of the house.

But what makes us feel like we are in the presence of a supernatural spirit? Are there possible scientific explanations for that tingling sensation you get on the back of your neck, or the sudden feeling of uneasiness with an origin you can’t quite place? Let’s investigate six possible explanations for that paranormal feeling that are rooted in science rather than the supernatural.

6 Possible Scientific Reasons for Ghosts

1. Low frequency sound
2. Mold
3. Carbon monoxide
4. The power of suggestion
5. Drafts
6. We enjoy being afraid

Here they are in more detail.

• 1. Low frequency sound

Just as the human eye can only see light at a range of frequencies—for example, we can’t see radio waves—the human ear can only hear sounds in a range of frequencies. Above ~20,000 Hertz, sounds are too high pitched for our ears to parse them, like the echolocation calls of most bats that fall in this ultrasonic range.

Similarly, human ears have trouble hearing low-frequency sounds below ~20 Hertz—known as infrasound—but such sounds do not go totally unnoticed. In a 2003 study, 22% of concert goers who were exposed to sounds at 17 Hertz reported feeling uneasy or sorrowful, getting chills, or “nervous feelings of revulsion and fear.”

So what are some of the more ordinary origins of such low frequency sounds? Weather events like earthquakes and volcanic activity or lightning, and communication between animals including elephants, whales, and hippos can all produce infrasound. And if you don’t live by any volcanoes or hippos but still think your house may be haunted? Humans also create low frequency sound via diesel engines, wind turbines, and some loud speakers or chemical explosions.

2. Mold

Breathing in toxic mold can be bad for your respiratory system, but it can also be bad for your brain. Exposure to mold is known to cause neurologic symptoms like delirium, dementia, or irrational fears. So is it a coincidence that the houses we suspect are haunted also tend to be in disrepair and so quite possibly full of toxic mold? Scientists have worked to draw a firm link between the presence of mold and reported ghost sightings, but so far the evidence is mostly anecdotal.

3. Carbon monoxide

Just as breathing in mold could lead us to see, hear, and feel things that aren’t really there, so too can breathing in too much carbon monoxide. We have carbon monoxide detectors in our homes to make sure we are not breathing in this odorless, colorless gas that slowly poisons us while going undetected by our senses.

But before a carbon monoxide gas leak poisons us, it can cause auditory hallucinations, a feeling of pressure on your chest, and an “unexplained feeling of dread.” An often-told ghost story from the 1920s about the H family who moved into a new house only to hear footsteps, see apparitions, and feel malicious paranormal presences, turned out to be the result of carbon monoxide poisoning from a broken furnace.

4. The power of suggestion

Studies suggest that we are more likely to believe in a paranormal experience if someone else who was there can back up our belief. So while we might be able to convince ourselves that we were somehow mistaken about what we saw or heard, we tend to put more stock into someone else’s eye witness account if it also backs our suspicions. So our belief in ghosts can be catching.

Similarly, I would like to extend an apology to anyone I ever played the game of Ouija with as a kid. The toy game board used to contact spirits always proved too tempting to resist so the one moving it was always me, and not a paranormal spirit, even though I was just as excited as everyone else.

5. Drafts

As the days get hotter and air conditioning becomes more and more expensive, I rely more on opening windows to cool my home. Opening windows on opposite ends of a room can create a nice breeze, but it can also create cold spots as air flow outside changes, causing cooler air to enter a warmer room. Drafts can also sneak in through chimneys and cause doors to slam or door knobs to rattle. So before you schedule a séance, try closing a few windows.

6. We enjoy being afraid.

Neurologists have found that our brains release dopamine, a chemical associated with pleasure, when we are afraid. Exactly how much dopamine and how many receptors we have for receiving it can influence whether you are a person that enjoys being frightened or someone who would rather avoid scary movies or rides altogether. So for some, letting our imaginations run wild with the possibilities of cohabitating with ghosts, athough scary, may also produce a bonus euphoric high.

Of course, believing in ghosts also allows us to believe in an existence after death, which ultimately can be comforting. That is, if you can get past the feeling that someone is standing just behind you as you read this.

ABOUT THE AUTHOR

Dr. Sabrina Stierwalt is an extragalactic astrophysicist at the California Institute of Technology and Adjunct Faculty at the University of Virginia. Stay in the science loop! Listen and subscribe to the Everyday Einstein show on Apple, Spotify, or wherever you get your podcasts.

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