As Mary Shelley described it, the inspiration for Frankenstein came to her all at once in a nighttime apparition: “I saw—with shut eyes, but acute mental vision—I saw the pale student of unhallowed arts kneeling beside the thing he had put together,” she wrote in the preface to the novel’s 1831 edition. “I saw the hideous phantom of a man stretched out, and then, on the working of some powerful engine, show signs of life, and stir with an uneasy, half-vital motion.”

Shelley’s version of events has been largely disputed in the years since Frankenstein’s publication, with some scholars arguing she invented a dramatic moment of inspiration to please her readers. But regardless of the truth of its origin story, Frankenstein was as much a product of the science of the day as it was of any nightmare.

At the time she began to write it, Shelley was vacationing outside Geneva with a group of intellectuals that included Lord Byron, physician John Polidori, and her husband, the poet Percy Shelley. Often, as she noted in the preface, the group’s evening discussions would turn to galvanism, the contraction of muscles stimulated by electricity—a newly-discovered phenomenon that captivated the scientists of the early 19th century. It captivated Shelley, too: “Perhaps a corpse would be re-animated; galvanism had given token of such things,” she wrote. “Perhaps the component parts of a creature might be manufactured, brought together, and endued with vital warmth.”

Shelley’s work—with dozens of movie adaptations and who knows how many Halloween costumes—is one of the most well-known examples of the intersection of science and horror, but her Dr. Frankenstein is far from the only scientist created specifically to scare. In H.G. Wells’ 1896 horror novel The Island of Doctor Moreau (and the 1996 Hollywood flop starring Marlon Brando), the titular character lives alone on a private island where he surgically reshapes humans into animals. Robert Louis Stevenson’s The Strange Case of Dr. Jekyll and Mr. Hyde has a mild-mannered scientist create a potion to curb his darker urges, only to have the drink strengthen his homicidal alternate personality. And in the film The Fly, made in 1958 and then again in 1986, a botched lab experiment on matter transportation transforms a researcher into a man-fly hybrid.

Today, many of the things that would once have seemed like horror-story fodder are scientific reality: Animals have been cloned, for example, and human faces have been transplanted. Surgical robots are trusted with human lives. But still, as the boundaries of human knowledge are continually pushed, the trope of the mad scientist endures. What is it about the character that makes it so chilling? When so much of Halloween is based on the supernatural—the ghosts, the goblins, the vampires—why are scientists so often lumped in with the rest of the haunted-house cast?

“Science and reason are supposed to be the antidote to paranormal beliefs, and yet fictional scientists often appear as villains of paranormal horror films,” psychologist Stuart Vyse recently noted in Psychology Today, and mad-scientist-themed decorations abound in seasonal aisles as October 31 approaches. “Halloween is a kind of Rorschach test of our common fears,he wrote.

I spoke to Vyse, a professor at Connecticut College who specializes in the psychology of superstition, about why the mad scientist is one of them.

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Cari Romm: What are some of the differences between the mad scientist and the typical horror villain?

Stuart Vyse: The typical horror villains, like Michael Meyers in Halloween and [Freddy Kreuger in] Nightmare on Elm Street, those are just sort of homicidal maniacs. They are mentally ill, psychopathic. They often have an overblown or misguided revenge motive to them. And they often seem to be superhuman—they survive under circumstances when others would not, or they have superhuman strength. So you have great power, and you have behavior that’s frightening because it’s so unpredictable and beyond the realm of normal experience. And then, of course, the basic thing, which is that they’re out to kill people.

In the case of the mad scientist, it’s interesting—only in some cases the scientist is truly described as being mad. Sometimes they are, which means they’re not going to share the same predictable forms of behavior or the same goals as others.

But other times it’s not so much that they’re mentally ill or psychopathic or even evil, but simply that their goals are wrong according to the moral structure of the story. They are too driven by curiosity to know—almost in a Garden of Eden sort of way—certain knowledge that shouldn’t be theirs, and yet they want it. And so you have that same sort of scene that goes through the Garden of Eden with Adam and Eve. There’s also the Faust legend, where Faust wanted to know things and experience things that were not supposed to be within his realm, and actually sold his soul to the devil in order to experience them. They’re almost infatuated or intoxicated by motivations that get us all in trouble.

Romm: What’s so frightening about that sense of curiosity?

Vyse: It’s the unintended consequences. For example, the motives for making genetically modified foods may be very good, and they may have a good end, but people fear that there are unknown side effects—that the foods that are made this way will have some other effect on them. So many of the advances of science have been shown to have side effects. They’re a mixed bag, and people worry about the downside of these achievements.

Romm: What would be an example of that?

Vyse: A contemporary example—it’s an old movie, but it’s been remade a number of times—is The Fly. He’s a scientist, he’s interested in learning how to transport objects from one place to another, but it goes awry. It’s a very sort of Faustian thing, where he ends up with knowledge that has an unintended consequence that’s scary. Even Frankenstein’s goals are not really evil. He may be sort of an egomaniac, taking on more power than he should be taking on. But he’s driven by an interest in science and wanting to see if he can do this—in some ways, it’s maybe even a positive goal, of wanting to cheat death.

But science is this powerful force that can produce unpredictable results. I grew up in the 50s and 60s, and back in that black-and-white horror film era, the great fear came from atomic energy. And Godzilla and all these sort of giant caterpillars and other things were supposed to have happened because of atomic energy. There was this fear, because of the bomb, of the power of science to create fearful creatures or to harm us in some way. That’s the equivalent of the typical villains, Halloween movie villains’ superhuman strength or unusual power. Science has that too. And so I think that’s part of the reason why scientists are sometimes placed in that fearful role.

Romm: Is there an equivalent modern fear? Something that’s taken the place of the giant radiation-infused monsters?

Vyse: I think that at the moment, the main fear is that science has an unholy alliance with profit motives—that with pharmaceutical companies and vaccines and GMOs, that science is being used in that way. There are a number of contemporary science-fiction films in which corporate interests [play a role]—for example, the first Alien movie, in which the corporation wants to keep the creature alive in order to see if there’s some commercial benefit to it. That’s the kind of thing that’s going on now.

Romm: In other realms, we don’t find the combination of genius and mental illness to be as threatening—there’s no “mad artist” trope, for example. Van Gogh isn’t scary. What is it about science in particular that makes the mad scientist frightening?

Vyse: It’s the idea that they have powerful knowledge. As an example, I’m an experimental psychologist. I’m a scientist. But if I’m traveling on an airplane and somebody asks me what I do for a living, if I say I’m a psychologist, they sort of become nervous and worried that I’m going to analyze them. There’s this sense that you have knowledge, that you’ll be able to find out things about me that I don’t want you to find out. And I think in the case of science, that’s exactly the case—that genius, combined with the power of science, is frightening, is potentially something that could be used against you in an evil way. If you think about it, there are a number of horror films in which the villain is a psychiatrist or a psychologist. It’s combining this idea of special knowledge that can be used powerfully to make that person frightening.

I would put Hannibal Lecter in a similar category. He’s not really a mad scientist, but part of what makes him so scary is that he’s so brilliant, and his great intelligence is in fact used against people.

Romm: You’ve done a lot of research on the psychology of superstition. How does the idea of the mad scientist fit in with that?

Vyse: Part of the fear of science comes from people who are not rational thinkers, who are motivated by emotion and fear and don’t have a good understanding of scientific processes. So for example, the evidence is there that the vaccines are safe, that there’s no great harm in taking them. There’s great benefit in taking them. In the scientific world, there’s no ambiguity about that. But people are just refusing to believe that and to accept that evidence, and instead are clinging to other ideas. And I do believe that one of the common threads in [superstition and fear of science] is a poor understanding of critical thinking, of the role of evidence in logic, in debate.

But here’s the irony: I know lots of people who are scientific thinkers who love those movies. And I grew up on them. So I’m not sure there’s any cause and effect relationship. It’s true that horror movies play upon aspects of science that are genuinely worthy of concern, and it’s easy to create a fearful character by mixing a little bit of unexpected scientific effect and maybe an unstable character who can’t be trusted. It makes for good drama. I would be hesitant to say that the real-life problem we have with acceptance of scientific thinking is encouraged or discouraged by movies, but it’s clear that the things people are afraid of in one domain also work in the movie domain.

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Sometimes, as was the case of Mary Shelley, science inspires art—and sometimes, art inspires science.

In Minnesota in 1931, a hundred years after Shelley described her inspiration for Frankenstein, Minnesota, a boy named Earl Bakken was captivated by actor Colin Clive’s portrayal of the mad scientist. “What intrigued me the most, as I sat through the movie again and again,” he later recalled, “was the creative spark of Dr. Frankenstein’s electricity. Through the power of his wildly flashing laboratory apparatus, the doctor restored life to the unliving.”

Decades later, Bakken—the founder of medical-device company Medtronic—would, through a creative spark of his own, invent the wearable, portable pacemaker.