Every week of the year, in rural Summertown, Tennessee, not too far from Nashville, retired Navy man Russ McKamey terrorizes people. McKamey Manor is a haunted house, but it's nothing you'd send your kid to for Halloween. It's billed to interested parties as "live your own horror movie."

McKamey spends as much time talking people out of the haunt as he does allowing them to come in. "'You really don't want to do this'—that's my tagline," McKamey tells Mental Floss. With his gravel-throated voice and quickness to laugh, his professed love of Turner Classic Movies and musicals, it's hard to imagine this father of two dreaming up these horror shows. He combines what he says are mind control techniques from "MK Ultra"—a notorious CIA project—and general hypnosis techniques with harrowing, gruesome stunts to break people down physically and mentally. "You will hallucinate when you're here," he chuckles. "You will be putty in my hands."

Though McKamey keeps the full details of the haunt under wraps, he posts short movies on his website of participants in horrifying scenarios: A young woman pants and shivers in a tiny chamber, her face distorted by a plastic mouth guard that stretches her cheeks garishly apart. A person appears to be strangled by a boa constrictor. A young man lies bloody in a room of knives where a masked man eats raw intestines and comes at him with a drill.

McKamey insists "it's all smoke and mirrors" and "under control," and that no one is ever seriously injured other than "cuts, bruises, and strains." But, he says, the physical challenges and mental terror are real. He even keeps an EMT on hand. This is why his selection process is so rigorous: "After they contact me, I don't even take them seriously until they get a letter from their doctor saying they're mentally and physically cleared to participate."

He only does one haunt per week, limited to two people at a time—surely a disappointment to the more than 40,000 people who apply to visit every year. (For 19 years, McKamey Manor was located in San Diego, California; it's only been in Tennessee for four months.) If they pass the initial screening, he runs a criminal background check on them. The day of the haunt he does a drug screening of the participants, who then have to sign a 40-page legal waiver in which they agree to a laundry list of all the possible horrors that could happen to them and release McKamey and crew from any liability.

Participants start out in "Holly's Playhouse," where they undertake a series of physical challenges. If they make it through that potentially hours-long ordeal, McKamey drives them two hours to another location in Huntsville, Alabama, where, he says, "it gets very mental and very serious."

While the participants don't know explicitly which experiences will occur in any given haunt, they sign off on the possibility that any of them could, ranging from having to escape from a coffin buried under 12 feet of dirt to having a fingernail pulled out with a pair of pliers. (Yes, really, though it's very rare and only done at the request of the participants.) They have a safe word they can use at any time to stop the experience.

Because of all this preparation, McKamey insists that nobody who comes to his haunt is an unsuspecting victim: "You've got to jump through serious hoops to get here. You've got to really want to do this."

Every show is personalized to the people coming through. Participants give McKamey permission to contact family, friends, and coworkers to probe deep into their fears. "We go for the gut wrenching—what really scares somebody," McKamey says.

The "winner" of the haunt—anyone who makes it through to the end, which can take long as 10 hours—wins $1000.

In the nearly two decades that McKamey has been operating his house of horror, nobody has ever completed the haunt.

On September 30, Sean Morin, a former military paratrooper and "horror junkie," and his wife, Kinsey, who will graduate from the police academy on Halloween, were the chosen two that McKamey—with the help of his girlfriend, Holly, and several volunteer actors—deigned to terrorize. The Morins, of Rossville, Georgia, were determined that they would be the first ones to survive every horror at McKamey Manor and take home that $1000.

"I'm pretty confident in making it through," Kinsey told Mental Floss on the day of their haunt.

Sean was excited. "I like the thrill of being scared: the surprises, the jump scares, the whole atmosphere of being immersed in an alternate reality," he said. For him, the adrenaline release relieves stress, anxiety and clears his head: "It's an escape from the hoopla of everyday routines."

Sean and Kinsey aren't alone in their love of being scared. And while McKamey Manor may be the most extreme version of a haunted house around, it's far from the only one.

Why do we do this to ourselves?

THE NEUROCHEMISTRY OF FEAR

Taking pleasure in fear is actually quite normal, it turns out. According to Kate Brownlowe, neuropsychiatrist and section chief of neurobehavioral health in the department of neurology and psychology at The Ohio State University Wexner Medical Center, being afraid is essential to human survival. "On an evolutionary basis, people who had a good fear response to things that were dangerous were far more likely to survive in the wild," she tells Mental Floss.

When your brain senses a threat of danger, often before your conscious mind has even had time to process it, a little almond-shaped structure in each lobe of the brain called the amygdala sends out excitatory signals that trigger your sympathetic nervous system into a fight-or-flight response. Corticotrophin releasing hormone (CRH), cortisol, and adrenaline surge into your blood, your heart rate increases, your pupils dilate, and you begin to sweat, creating a strong state of arousal, or alertness, to prepare you for action. New research has even recently identified neural pathways that process fear, involving the hippocampus, actively involved in memory, which may shed light on how to intervene upon trauma and PTSD.

However, once your brain has determined that you will not die from this threat, or that the threat is largely over, your frontal lobes take over. "The experience of your brain calming itself down is actually very pleasurable," Brownlowe says, which may be why people come back for more. The parasympathetic nervous system kicks into "rest-and-digest" mode, which releases the feel good neurotransmitter dopamine. There's also psychological benefit—surviving a scare can "reset the thermostat for people" so that things which had seemed intimidating may be easier to deal with in the future. "It's easier for the frontal lobe to calm down the fear response because you already have that belief: that expectation that you're going to be OK," Brownlowe says.

Belief may play a big part in how scared we get, in fact. "There's no fear without belief," Craig April, Ph.D., therapist and founder of the April Center for Anxiety Attack Management in Los Angeles, tells Mental Floss. In his treatment of people with anxiety disorders, April devotes much of the work to challenging people's beliefs about what evokes their fear, and helping them change those beliefs through cognitive behavioral therapy.

"Life is so uncertain, and uncertainty always brings some measure of fear," he says. He believes that people may be drawn to horror and fear-inducing events as a way of trying to gain mastery over that which scares us in our own lives: "When going to a haunted house or movie, our brains have a sense that this is a controlled environment, so even though there's a lot of uncertainty, if we faced those fears, it can be empowering."

Unless, of course, you have damage to your amygdala, in which case it is possible for your fear center to go down like a power line in a storm. In one rare case documented in 2010, a woman with lesions on her amygdala, identified only as "SM," lost her ability to feel fear. She might be McKamey Manor's ideal candidate, for when researchers at the University of Iowa exposed her to live snakes and spiders (to which SM expressed a lifelong hatred), took her on a haunted tour of Waverly Hills Sanatorium, and showed her a series of horror films, she remained unmoved and unafraid. She was actually drawn to the most poisonous of the snakes and spiders. Moreover, she was also still able to "exhibit other basic emotions and experience the respective feelings."

THE CONNECTION BETWEEN HORROR AND IMAGINATION

While fear is a deeply intrinsic part of every mammal's ability to stay alive, horror may be a strictly human phenomenon, as McKamey Manor makes sure to play upon. In a 2014 paper published in the journal Social Research, philosopher and author of the book On Monsters: An Unnatural History of Our Worst Fears, Stephen Asma looks to horror master H.P. Lovecraft to delineate the difference between horror and fear. "Lovecraft argues, in his 1927 Supernatural Horror in Literature, that good horror evokes a unique subjective emotion, which he refers to as ‘cosmic fear,'" Asma writes. "There is something in the horror experience, Lovecraft claims, that resonates a deep instinctual awe of the unknown."

Most mammals experience fear in relationship to "specific enemies," he says, namely other creatures and forces that can kill them. But in humans, with our comparatively larger neocortexes, "we can take our memories, ideas, goals, and emotions offline, so to speak, and entertain them in a parallel universe of mental space." In other words, our ability to imagine increases our ability to feel horror.

This might explain why researchers from Indiana University Media School found that the brains and emotions of people who play horror games like Resident Evil or Amnesia: The Dark Descent can't distinguish between "fake" fear and real fear. In keeping with April's theory, the researchers suggest that people seek out fear in controlled experiences, such as playing video games. When you know an experience can't harm you, there's a temporary rush, and then a period of relief when the thrill is over. While the experience itself might be fake, the fear is real.

And not only is it real in your mind, it's real in your blood. If you've ever described your experience of a scary movie as "bloodcurdling," you are more correct than you know. The term dates back to medieval times and is based on the concept that fear or horror would ‘run the blood cold' or ‘curdle' blood," according to a 2015 study out of Leiden University Medical Centre in Germany, published in the medical journal BMJ.

Researchers set out to test the truth of this by studying the effects of fear on markers of blood coagulation in participants watching movies. The researchers took blood samples before and after the subjects watched two 90-minute movies, one educational and the other horror. They also had participants answer a questionnaire to determine if they were scared by the horror movie. They found that coagulant factor VIII levels before and after watching the horror movies were higher than for the educational movie.

Researchers from the Aarhus University School of Communication and Culture in Denmark who presented at the 29th Human Behavior and Evolution Society conference in 2017 suggest that there's an evolutionary explanation for these responses, in that "horror may be analyzed as a simulation technology that allows users to attain adaptive experience with perceived threat and negative emotion in a safe environment," they write.

GORE, DISGUST, AND RISK

Not all fear is created equal, of course. McKamey Manor capitalizes on blood and gore—no matter how fake—as a big sell to horror junkies. Gore is a key component of contemporary horror movies, ranging from the grotesque assaults of the Nightmare on Elm Street films featuring the terrifying Freddy Krueger to the popular guts-and-gore Saw slasher films of today.

While it might seem unlikely for the average person to take pleasure in viscera and violence, a 2014 study in the Journal of Communication found that movies and shows with gory and disgusting scenes have a higher likelihood of holding an audience's attention than those without. Researchers at University of Central Florida exposed 120 participants to images that fell into three categories of disgust: body envelope violations (a "core disgust," in which an individual's skin has been penetrated or harmed in such a way that leads to injury or death); body products (another core disgust, dealing with fluids and wastes produced by a body, such as vomit and feces); and sociomoral disgust (which occurs when watching people engaged in hate speech or sexual abuse).

When the researchers introduced stimuli via TV or movies that elicited one of these forms of disgust, it turned on the sympathetic nervous system, creating a state of readiness much like that involved in fight-or-flight. The core disgusts are especially effective at flipping the switch on.

The authors theorize that there is an evolutionary bias toward disgust, because it "would better equip humans to avoid harmful substances. Disgust-related contaminants are often tied to survival opportunities like food and sex, providing even more motivation for one to correctly identify potential threats."

On a primal level, gore tells the animal part of our brains that there is something serious that requires our attention.

With all this evidence for the functions of fear, why do some people actively seek out being afraid while others do not? According to Frank Farley, Ph.D., a psychologist and professor at Temple University in Philadelphia, and the former president of the American Psychological Association, tolerance or avoidance of fear-inducing events is shaped by "a recipe of ingredients" that includes brain processes, genetics, social experiences and influences, childhood upbringing, and the culture or community in which a person lives.

Farley has spent 40 years identifying what he calls "T Type" personalities (T is for "thrill"). All of us exist on a spectrum of "sensation seeking," a well-understood psychological principle, he tells Mental Floss. Those with high sensation–seeking needs are your horror junkies and thrill seekers: "T types thrive in the realm of uncertainty." These are the people who climb Mount Everest, despite high risk of death. Who like to throw themselves out of planes or slackline over canyons. While these types undertake a high degree of personal risk, Farley credits them with being highly "inventive, creative and innovative."

"You're never going to do great creative things in this world unless you're a risk taker," he says. These are Big T types, which he calls "the change agents, adventurers, pushing the envelope all the time."

On the other end of the spectrum are the Small T types—those of us who are risk averse or avoidant—who are "holding onto the handrails of life."

The people who fly from all over the country to partake in McKamey Manor's horrors are likely Big T types.

HAUNT, INTERRUPTED

After nearly two decades, McKamey still finds himself fascinated by people's draw to his haunt. The local community thinks of him as "evil," he says—and he claims to have gotten death threats. "People think in order to do this I must be some psychopath. If you actually knew me, you just say, 'You're actually just a good guy.'"

This good guy managed to absolutely terrify former paratrooper Sean and cop-to-be Kinsey. Despite their confidence before crossing the threshold of McKamey Manor, the couple did not make it through the haunt. In fact, they only held up through one entire stunt out of hundreds.

While McKamey won't disclose the full details of the experience that did them in, he describes it as a "height stunt." Sean and Kinsey were blindfolded, their ears were covered with noise-canceling headphones, and their mouths were plugged with an uncomfortable plastic mouth guard. For Sean, the deprivation of his senses combined with the uncertainty of how far he might fall added up to a complete loss of control. "There was no way I was going to be able to gain control of myself with my senses being taken away," Sean says.

Of the experience, McKamey says, "Physically it's not that tough, but your mind will always be your worst enemy."

There were also points at which Sean was scared he would have to stop "for an emergency reason, like water going into my lungs." (Water is a constant in almost all the experiences for its power to wear down one's mental and physical resources, McKamey says.)

During the transition between the height stunt and the next one, Sean ran into a tree with such force, he nearly knocked himself out. It was at that point that he felt he couldn't go on.

"I was disappointed in myself," Sean admits.

He calls McKamey Manor a "a great experience"—and he wants to do it again. Undaunted by their failure, he and Kinsey plan to return in the future to try to survive their fears.