On the Saturday before Halloween I went on a haunted tour of the Merchant’s House Museum, where my roommate volunteers as a guide. The museum, a grand brick house on East 4th Street, is the oldest single-family home in New York City. It was built in 1832, and the family who lived there did so for nearly 100 years, until the daughter of the family, Gertrude, died in 1933 at 93 years old. It is at that point that she may or may not have turned into a ghost and started haunting her former home.

According to the tour guide—a co-volunteer of my roommate, who, during my visit, was on flashlight rather than speaking duty—Gertrude was seen in the street scolding a group of rowdy young boys just days after her death. Just days after! (I don’t know why this makes it seem extra weird and kind of funny. It just seems to me that hauntings, in an ideal world, would more logically take at least a few years after the death in question to kick in. Dead people should take a break first. To do it any other way is just rude, and, I would think, would be less effective in achieving shock value.)

But from that day on, people—visitors to the house, staff members, contractors doing repairs on the house—kept seeing her. Sometimes she looked like she did when she died, and sometimes she was young. People would say they saw a woman in period dress in the hall or at the top of the stairs and, later, when showed a picture of Gertrude Tredwell by someone affiliated with the museum, they’d say, “That’s her."

If you’re neither a believer nor feeling very generous, this manner of identifying a ghost seems like a clear example of fitting the evidence to the theory after the fact. There is no true side-by-side comparison to be had; people who believe they’ve just seen a ghost of a woman in an old dress are shown a picture of a woman in an old dress and, naturally, nine out of 10 of them will probably find that it’s a startling match. Either you’re the type of person who wants to make something of what she’s just seen, or you’re not.

"I have very wealthy people here. They think it's the coolest thing there is."

IN 1994, TWO ENGLISH psychologists, Susan Blackmore and Rachel Moore, published a study called “Seeing Things: Visual Recognition and Belief in the Paranormal.” People tend to believe a number of weird and ultimately wrong things that might contribute to a belief in the paranormal, they surmised: We tend to think we’re more in control than we really are, we think the likelihood that any event is due to chance is much lower than it really is, we never want to think any series of occurrences could be purely random. As a species, we like to attach meaning and form to the things around us. A spilled coffee plus a missed train plus a mild scolding from a supervisor turns into a bad luck streak we’re doomed to suffer through, rather than a set of three unrelated events that just happened to fall together on one day. Similarly, for a sizable portion of us, a thump plus a flash of light plus a curtain that moved a bit oddly turns into, maybe, a ghost.

For their study, Blackmore and Moore enlisted 30 undergraduates at the University of Bristol, all of whom were shown sets of black-and-white pictures that were distorted with varying levels of computer-generated noise. The students were told to examine the pictures and then asked whether they recognized anything and, if so, what it was they saw. But there wasn’t actually anything pictured in any of them.

The students took a separate questionnaire that gauged their belief in the paranormal, and the researchers used this to see whether that belief corresponded to an increased tendency to identify images and people where none existed. Perhaps unsurprisingly, it did—those participants who expressed a belief in the paranormal were more likely to claim they could identify images among the noise in the photographs they were shown. Less expected might be the researchers’ finding that the believers were even more likely to identify something specific from among the noisiest, darkest, least-clear photographs. (You have to feel a little embarrassed for the students, here. “It’s the face of a tiger.” “Are you sure?” asks the researcher, trying not to laugh. “Yes,” they reply, so misguidedly confident. “I’m certain.”)

This false sense of recognition—seeing significance in a random stimulus—is a phenomenon called pareidolia. It’s a term more typically associated with seeing faces and religious imagery, especially in ordinary objects (think Jesus Christ on a grilled cheese sandwich), but some, including Blackmore and Moore, suspect it might have a lot to do with why certain people see ghosts. Or hear them—the identification of electronic voice phenomenon (EVP) as paranormal has been called auditory pareidolia.

AT THE END OF most episodes of Ghost Hunters, the hosts would play one of the recordings they collected while filming overnight. The clarity of sound on these recordings varied dramatically. Sometimes you’d hear what they heard, and it was small but unsettling. Sometimes, though, they’d play a series of whiny scratches and come up with something hilariously specific that was allegedly being said—“It was Colonel Mustard in the library with the candlestick,” or similar—and you wouldn’t hear it at all. This never stopped me from watching the next episode that came on, so Blackmore and Moore would probably say I’ve got pareidolia. But I’ve always thought it silly to try to explain ghosts (or explain them away) with science. Whether it’s because I’m a little salty at the fact that Blackmore and Moore called ghost-believers “sheep” in their study or because I want to think more highly of myself than perhaps I deserve, I think what pareidolia (and even half-hearted belief in ghosts, for that matter) comes down to is whether or not you have an imagination you’re willing to indulge.

They played us an EVP recording at the Merchant’s House Museum that night—first you hear the ghost hunter introducing himself to whichever spirits might be there, telling them not to fear him. After that there’s a little creak. Then they play it back, cleaning up the background noise, and I’m sure that everyone in the room could hear it if they wanted: a little girl, answering, “I’m not afraid.”

“Is this the voice of a young Gertrude Tredwell, frozen here in time as a child?” the tour guides asked. I nodded. Why not?