DENISE STONER WAS 2½ years old the first time she remembers the alien taking her. She was at home in Hartford with her grandfather. Her mother was at the hospital giving birth to her younger sister. She remembers staring out a large picture window and seeing an egg-shaped object in the sky, hovering over some power lines. “What’s Humpty Dumpty doing up in the sky?” she asked. She remembers the fear in her grandfather’s face when he suggested it was time for bed.

Later that night, as she lay staring at her nursery rhyme-themed wallpaper, an entity walked through her wall. “He looked like a monk, he had a robe, and he was carrying a light. I wasn’t afraid of him,” she said. “He put out his other hand for me to take it, and I did. We walked out into the hallway.” The alien pointed his light at the wall, and they disappeared through it; she remembers being in a large, dome-shaped room with a lot of other children, and they seemed to be learning something. In the morning, she was back in her bed.

Since then, she says, she has been taken more than 50 times, from her home, from the street, from her car, the last time only three years ago, driving through the mountains in Colorado. Each time, it’s the same being responsible. “He looks like your typical gray [alien], but he’s one of the tall ones. It’s just the very subtle shape of his face, his chin is a little wider,” she explained. She calls him her escort. “There’s no friendship. . . . He comes to get me, and I know I’m going to be safe,” she said. “He’s also going to oversee whatever is done.”

Stoner, 68, lives in Florida with her husband. Now retired, she works with fellow “experiencers,” people who feel they have had contact with intelligent nonhuman entities. She also conducts investigations on behalf of the Mutual UFO Network, or MUFON. Being an experiencer is very much part of her identity. Her story is coherent, she doesn’t ramble or get lost in the telling.

Do you believe her?

If you said yes, then you might be among the 77 percent of Americans, according to a 2012 National Geographic poll, who believe that aliens have visited Earth, or the 30 percent of Americans who believe that the government has covered up evidence of alien visitation, according to a 2015 YouGov poll. Or maybe it’s happened to you: There are few hard numbers, however, a 2014 survey for a British talk show found that one in 25 respondents believed they’d been abducted by aliens.

Belief that alien life exists on other planets is persuasive, sensible; nearly 80 percent of Americans do believe it, according to a 2015 poll. But belief that the aliens are already here feels like something else, largely because it requires a leap of faith longer than agreeing that the universe is a vast, unknowable place. Abduction and contact stories aren’t quite the fodder for daytime talk show and New York Times bestsellers they were a few decades ago. The Weekly World News is no longer peddling stories about Hillary Clinton’s alien baby at the supermarket checkout line. Today, credulous stories of alien visitation rarely crack the mainstream media, however much they thrive on niche TV channels and Internet forums. But we also still want to believe in accounts that scientists, skeptics, and psychologists say there is no credible evidence to support.

The abduction phenomenon began with strange case of Betty and Barney Hill. On Sept. 19, 1961, the Hills were driving from Montreal to their home in Portsmouth, N.H. Betty spotted a UFO following them. Barney stopped the car on the highway, near Indian Head in the White Mountains, and got out to look at the craft through binoculars. Seeing humanoid figures in Nazi-like uniforms peering through its windows, he ran back to the car, screaming, “Oh my God, we’re going to be captured!” They drove off, but two hours later, they found themselves 35 miles from the spot where they’d first seen the craft (there is now a commemorative marker at the site), with little memory of how they’d gotten there. Soon after, Betty began having nightmares.

In 1964, the Hills underwent hypnotherapy. Under hypnotic regression — hypnosis with the intent to help a subject recall certain events with more clarity — the couple said that they had actually been pulled on board the vessel by aliens and subjected to invasive experiments. The Hills’ story, revealed to the public in 1965 with an article in the Boston Traveler and a year later in the book “The Interrupted Journey,” launched a flurry of public fascination with abductions.

Barney died of a cerebral hemorrhage in 1969, but Betty went on to become a kind of sage of paranormal experiences. Their story became the blueprint for alien abduction experiences in the years that followed, especially after the airing of the 1975 made-for-TV film “The UFO Incident,” starring James Earl Jones as Barney Hill. Subsequent experiencers would describe similar missing time or have bizarre dreams and flashbacks of things they couldn’t understand. Many would use hypnotic regression to recall their experiences.

Over the next two decades, the alien abduction narrative wound its way into the American consciousness, fed by science fiction films like “Close Encounters of the Third Kind” and breathless news reports of mysterious incidents. In 1966, a Gallup poll asked Americans if they’d ever seen a UFO; 5 percent said they had, but they meant it in the literal sense of an unidentified flying object — only 7 percent of Americans believed that the UFOs were from outer space. By 1986, a Public Opinion Laboratory poll found that 43 percent of respondents agreed with the statement: “It is likely that some of the UFOs that have been reported are really space vehicles from other civilizations.”

Some experiencers said the aliens were here to save us and study us, some said they were here to harvest our organs and enslave us. But by the late 1980s, people whose stories would have been dismissed as delusional a generation earlier were beinginterviewed by Oprah and “true stories” of alien experience, such as Whitley Strieber’s “Communion” and Budd Hopkins’s “Intruders,” were bestsellers. By the 1990s, those who believed in the literal truth of alien abduction stories gained an important ally in John Mack, a Harvard professor and psychiatrist who compiled his study of the phenomenon into a 1994 book titled “Abduction: Human Encounters with Aliens.” He later told the BBC, “I would never say there are aliens taking people away . . . but I would say there is a compelling, powerful phenomenon here that I can’t account for in any other way.”

“These books sold really, really well, they were on book racks in airports and railway stations. You couldn’t really avoid it,” said Dr. Chris French, head of the anomalistic psychology department at Goldsmiths College in London and author of a study on alien abductees. And it wasn’t just books — one of the most popular television shows of the 1990s was devoted almost entirely to alien conspiracy theory: “The X-Files.” “All of these things influence people’s beliefs about what might be true, what might be plausible,” said French.

Other social currents, some of them peculiarly American, informed these stories and our interest in them. Space exploration in the 1950s and ’60s forced the country to admit that a vast unknown lay beyond our atmosphere — at the same time, the Cold War inspired existential fear of invasion. The 1960s and ’70s were attended by horizon-broadening mysticism, publicized experimentation with drugs — people talked about out-of-body experiences. The 1980s saw an explosion of angst around “stranger danger,” with a near-constant reports of child abduction and sexual molestation, and then, recovered and repressed memory. Alien abduction stories absorbed those strains, re-inventing them as anal probes and sinister hybrid breeding programs.

Meanwhile, psychologists like French were examining alien abduction narratives from a more skeptical perspective. And what they found is that the truth wasn’t so much out there as it was in our heads. “People have weird experiences in all societies, given that our nervous systems are the same the world over,” explained French. “It’s the interpretations that might differ.”

A small but stubborn percentage of alien abduction experiences defy clear scientific explanation, but many of the rest can have a number of different physiological or psychological explanations, including epilepsy, which can be preceded by visual disruptions, narcolepsy, or sleep paralysis.

In normal sleep, your body is relaxed nearly to the point of paralysis, presumably to keep you from acting out your dreams. Sleep paralysis is a disruption of lucid dreaming in which the mind partially wakes but finds that the body has not. It can be terrifying: Individuals report sensing entities in the room with them and being unable to move, pressure on their chests, out-of-body-like sensations coupled with intense, heightened emotions. In the past and in other cultural contexts, this experience was attributed to demons or evil spirits or a religious phenomenon. In America, science fiction was increasingly part of mainstream entertainment, and stories about alien contact experiences were covered as news, so aliens seemed like a plausible explanation for these experiences.

Then there’s the slippery nature of memory itself. The richness of a remembered experience is no guarantee of its objective reality, even less so if that memory was “recalled” through hypnotic regression. Though now largely dismissed by mainstream psychology, hypnotic regression remains popular with experiencers. Psychologists say that discerning true memories of actual events from true memories of imagined events is impossible, especially if the individual was predisposed to believe in paranormal or alien experiences.

Additionally, there’s old-fashioned hallucination. A recent international survey of more than 30,000 people, none of who were diagnosed with schizophrenia or other mental health issues, found that 6 percent of them reported experiencing a hallucination unrelated to drugs, alcohol, or sleep. Finally, Michael Shermer, prominent American skeptic and columnist for Scientific American, notes, “Sometimes people just make stuff up.”

By the end of the 1990s, the alien abduction bubble had burst. Ratings fell for the “The X-Files.” In April 2001, reports (later denied) circulated that the British Flying Saucer Bureau, 1,500 members strong at its peak, was shutting down after a long dry spell of no sightings. Five months later, two planes crashed into the Twin Towers and no one cared about little green men anymore. “X-Files” director Chris Carter, at the 2008 San Diego Comic Con, declared that after 9/11, the mood just wasn’t right anymore. In 2006, Ben Macintyre, columnist for The Times, declared that the Internet had undermined belief in UFOs and alien visitation: “The unidentified flying object has been identified, and cannot fly any more. ET has gone home.” Skepticism, it seemed, had killed the UFO.

Except that it hadn’t. Not really.

David Clarke is a UFO researcher who investigated the British government’s UFO files — a former believer, he’s now a skeptic and author of several books, including “How UFOs Conquered the World.” In his view, the Internet didn’t kill alien belief so much as offer up hundreds of echo chambers for it to thrive in. “I think there are just as many people who believe that these things happen, but I think that they’ve retreated from public view and they just talk to themselves,” said Clarke. “In order for you to be a party to that, you need to buy into that reality.”

Skeptics want to believe that fewer people believe, that more people are aware of explanations like sleep paralysis or false memories. “People are capable of these fantastic experiences without them being real outside of the brain,” said Shermer, adding, too, that the camera-phone age is increasing the burden of evidence on experiencers.

Experiencers want to believe that public skepticism is subsiding. Rosemary Ellen Guiley, a prolific American writer about paranormal and mystical experiences, explained, “More people are willing to talk about their experiences because media has opened the door, because there has been a lot of media attention on all kinds of experiences, positive and negative. . . . This is validating, that they can talk about it and not be ridiculed.”

Yet if periodic polls are any indication, Americans have remained consistent on the subject of aliens for the last three decades. At any given moment, roughly 10 percent of Americans believe they’ve seen a UFO. A Gallup poll from 1990 found that 47 percent of respondents believed UFOs were “real,” as in alien. A 2015 Ipsos poll found that 56 percent of Americans believed in UFOs. American disbelief of the government line on UFOs has also remained steady. In 1996, 71 percent thought the government was hiding something; it was 79 percent in 2012, according to a National Geographic Survey. In other words, more people believe that the US government is covering up evidence of alien life than believe that Jesus is the son of God (a 2013 Harris Poll survey found that 68 percent of respondents believed Christianity’s central tenet). That makes Hillary Clinton’s campaign promise to open up files on Area 51 look all the more canny.

It also points to a strange moment for us humans, for how our understanding of our place in the universe has changed over the last 50 years. “We’ve become more materialistic, scientific, secular, and yet we are exactly the same human beings . . . with the same physiological and psychological makeup. Our brains are hard-wired to believe in something other than ourselves,” said Clarke. “People will carry on believing it because I think it’s just a natural part of what we are.”

On that point, some skeptics and some believers agree. There’s a long history of anomalous experiences attributed to angels, fairies, gods, and monsters — nonhuman contact experiences made to fit a cultural context. Those experiences point to something common in human consciousness. “We have had experiences throughout history that demonstrate that we are connected to something greater than ourselves,” Guiley said.

Or maybe not. In 1979, Pulitzer Prize-winning poet James Merrill published “Mirabell: Books of Number,” a work transcribing the poet’s conversations with spirits using a Ouija board. “If the spirits aren’t external, how astonishing the mediums become!” he said in an interview. The implication is perhaps disappointing — it’s not spirits, it’s not aliens, it’s just us — but also beautiful. And useful. “Investing time and money into why people have these kinds of extraordinary experiences might help us to answer fundamental questions that we don’t have answers for, like why do we have consciousness? I don’t believe in aliens, but I do believe that something unusual is happening to these people and it ought to be studied,” said Clarke.

Solving those riddles takes a lot of serious work, leads to a lot of dead ends, and might not prove satisfying even if we arrive at answers. Which is why, in the end, it may just be easier to attribute to aliens all the many wonderful things that we simply do not understand about the condition of being human.

Linda Rodriguez McRobbie is an American freelance writer living in London.