Why We See "Ghosts," According To Science
Cavan Images/Cavan/Getty Images

Although I am endlessly fascinated by the supernatural, I haven’t yet decided whether or not I believe in ghosts. As much as my ghost story-loving soul wants to believe in them, though, I’m leaning towards a big ‘ol “nope” — and the many scientific explanations for why we see ghosts are a big part of the reason why. A recent video produced by Vox breaks down a bunch of these explanations, and, well… they’re hard to argue with. This might be one case where Occam’s razor isn’t necessarily the way to go.

For the video, Vox spoke with Joe Nickell, the senior research fellow for the Committee for Skeptical Inquiry — or, as Nickell puts it, “the world’s only full-time, salaried, professional, science-based paranormal investigator.” Nickell’s methods are notable: He doesn’t go into any given case planning either to promote or debunk it; he just goes in planning to explain it. The difference matters, because it means he doesn’t have a specific agenda or any preconceived notions about what he may or may not find when he begins an investigation — so, instead of trying to make the evidence he finds fit a theory he already has (either unconsciously or as a deliberate choice), he just looks at what the evidence is trying to tell him on its own.

His conclusions, though, might disappoint some: Nickell says that he has never once seen anything he thought was actually proof of a ghost or haunting — nor, he notes, has science ever authenticated a ghost or haunting. So: If we honestly have no evidence that ghosts exist, why do we believe in them anyway? What do we really see or experience when we think we’ve seen or experienced a ghost or ghostly presence? According to a 2009 study from the Pew Research Center, 18 percent of American adults—that’s one in five, a not-insignificant number — said they’ve either seen or been in the presence of a ghost, while a whopping 29 percent said they’d felt in touch with someone who had died. If ghosts don’t exist, then what, exactly, are all these people experiencing?

A lot of what we experience as “ghosts” has to do with ambiguity, argues the video: When we see something occur, but we can’t see how or why it occurred, the ambiguity of the situation often prompts us to fill in the gaps ourselves — and often, we fill it in with something “supernatural.” In fact, though, there are plenty of real-life phenomena that provide perfectly logical explanations for what we perceive to be “ghosts.” Here are five of them:

Check out the entire 'What's Up, Boo?' series and other videos on Facebook and the Bustle app across Apple TV, Roku, and Amazon Fire TV.


You’ve Been Exposed To Infrasound

The range of human hearing is generally between 20 Hz and 20kHz. We’re still sensitive to sounds that are outside that range, though — and infrasound, which covers sounds below 20 Hz, can often make us feel really uneasy, even if we don’t know why we’re feeling that way. The Vox video notes that infra sound can induce feelings of depression, chills, a weird sense that there’s someone else in the room with you, and even visual hallucinations.

Here’s the key: A whole lot of normal, everyday things can produce noises at infrasound levels. Severe weather? Infrasound. Humpback whales? Infrasound. Machinery? Infrasound. Indeed, in one study conducted in 2003, researchers played four pieces of contemporary live music, some of which included infrasound, for listeners at a concert hall in London and found that 22 percent of the participants reported feelings of unease or sorrow, getting chills down their spines, or feeling revulsion or fear when they listened to the music with infrasound. Said Professor Richard Wiseman, a psychologist at the University of Hertfordshire, “These results suggest that low frequency sound can cause people to have unusual experiences even though they cannot consciously detect infrasound.”

(If you listen to The Black Tapes Podcast, here’s a theory for you: Maybe the Unsound is actually just infrasound. Thoughts?)


You’ve Experienced “Misperceived Self-Representation”

In 2014, researchers in Switzerland were able to induce “OMG I’ve just been touched by a ghost” feelings in participants in a lab setting. For the experiment, participants used a robotic device controlled by their fingers that let them manipulate how a mechanical arm moved. Another robot positioned behind the participants received these movements and used them to touch the participants’ backs. The participants said that when they both manipulated the robot in front of them and felt the other robot touch their backs at the same time, it felt kind of like they were touching their own backs. But, when the back-touching robot was set up to delay the movement by about 500 milliseconds, causing the back-touching to occur out of sync with their finger movements, the volunteers said that they felt like they were being watched and touched by at least one “ghostly presence.”

Now, yes, it’s unlikely that most people will find themselves in this sort of situation in their everyday lives. But the concept to note here is what’s called “misperceived self-representation,” and it can be caused by more than just robots. Said study co-author Dr. Giulio Rognini to the Telegraph, “Our brain possesses several representations of our body in space. Under normal conditions, it is able to assemble a unified self-perception of the self from these representations. But when the system malfunctions because of disease — or, in this case, a robot — this can sometimes create a second representation of one’s own body, which is no longer perceived as ‘me,’ but as someone else, a ‘presence.’”


You’ve Had An Episode Of Sleep Paralysis

Said Joe Nickell to Vox, “We can actually have people see ghosts, and those tend to be waking dreams that occurred in the twilight between being fully asleep and fully awake.” There’s a scientific name for this state, as well, Vox's video reminds us: We call it sleep paralysis.

As Bustle’s Claire Warner described it in 2016:

Sleep paralysis is the result of a mismatch between your brain and your body during transitions from REM sleep. During this stage, your body's voluntary movements are temporarily paralyzed to prevent you from acting out your dreams. This is actually a good thing (no one wants to wake up having accidentally punched a lamp because you thought you were punching something in your dream), but when your mind wakes up before your body is capable of moving again, the result is pretty terrifying.

Sleep paralysis is often accompanied by a feeling of dread, and you can experience hallucinations during an episode. If you don’t totally know what’s going on — or if you’re not aware you were even asleep — what you experience during these episodes could very well feel supernatural.


You’re Grieving

If you’ve lost a loved one recently, you might be more likely to “see” a ghost; according to research out of the University of Milan and published in 2016, six in 10 people report seeing the “ghost” of a loved one after their death. Another earlier study out of the University of Goteberg found that when elderly people lose their partners, 80 percent of them experience hallucinations associated with these partners a month after their passing. Seeing "ghosts" can be part of our grieving process — something that helps us cope with loss.


You’re Surrounded By Toxic Mold

This one isn’t covered by the Vox video, but I think it’s worth bringing up while we’re on the subject: In 2015, researchers at Clarkson University began a study assessing a theory of whether “ghost sightings” might actually be hallucinations brought on by the presence of toxic mold. “[Hauntings] are often reported in older-built structures that may also suffer poor air quality,” said study lead Shane Rogers, then Associate Professor of Civil and Environmental Engineering, in a press release. “Similarly, some people have reported depression, anxiety, and other effects from exposure to biological pollutants in indoor air. We are trying to determine whether some reported hauntings maybe linked to specific pollutants found in indoor air.” The results of the study haven’t yet been published, but it’s a plausible theory; I’m keeping my ear to the ground for whatever the researchers do (or don’t) find.

But whether or not ghosts exist, I think the idea of ghosts is an important one—even,perhaps, part of what makes us human. And although they’re sometimes thought of as scary or frightening, Joe Nickell notes that often, “the paranormal promotes something very positive.” He adds, “[They] all have to do with our hopes and our fears. We’re hopeful that ghosts exist, because then we don’t really die. Our loved ones are not gone from us.”

So, I mean, hey. If you believe in ghosts, then by all means, keep your belief alive. If it helps you in some way, shape, or form, then that’s really all that matters.