On any gloomy day, Michele Sinesky asks her husband to find a good monster movie on television -- "The Thing" or "The Tingler."
"You name it, I've seen it twice," said the 63-year-old grandmother of four from Charlottesville, Va. "For one thing, it's an old-time memory back to my childhood when we kids would tell each other spooky stories late at night at sleepovers -- the sense of someone saying 'boo' to you."
"But I also get an adrenaline rush when the monster jumps out at me," said Sinesky. "It's really fun when you can sit there and grab someone's arm or thigh."
For those who like the genre, a good horror movie arouses a cocktail of chemistry in the cerebral cortex -- the part of the brain that controls memory, perception and consciousness.
And it's not just movies, but amusement park rides and even books and fairy tales that can elicit simultaneously both pleasure and gripping fear.
As Oct. 31 approaches, businesses are capitalizing on the psychology of fear -- the spine-tingling sensation and the joy that goes with it.
This year, Americans will spend $6.9 billion on Halloween horror -- costumes, haunted houses and fright fests -- according to the National Retail Federation.
"We don't have many other holidays that are really directly connected to a strong emotion that is almost universal -- fear and the dark side," said Frank Farley, a professor of psychology at Temple University who specializes in thrill-seeking and extreme behavior.
"The fear business is institutionalized and I wonder if the positive or negative reliving of horror -- setting aside a day -- does that take the sting out of fear?"
The third film in the low-budget "Paranormal Activity" series grossed $54 million over the weekend, making it the highest ever for a film released in October, according to The Wall Street Journal.
One 2007 study published in Science Daily dispelled earlier assumptions that humans respond to pleasure and avoid pain: "It certainly seems counterintuitive that so many people would voluntarily immerse themselves in almost two hours of fear, disgust and terror. Why do people pay for this? How is this enjoyable?"
Researchers from the University of California and University of Florida concluded what most thrill-seekers know: People can experience both fear and euphoria at the same time.
"Pleasant moments of a particular event may also be the most fearful," it concluded, comparing horror movies to the thrill and fear of extreme sports.
But not everyone likes being scared, according to psychologist Farley, and how a person responds to fear is wired in their personality.
Those who thrive on fear are so-called T-types -- they are thrill-seekers, according to Farley, who coined the term in the 1980s.
"They like uncertainty, suspense, unpredictability, the unknown," he said. "Uncertainty is the prime source of fear. You don't know what's going to happen."
Movie makers and amusement park ride creators know how to induce fear. "There is intensity of stimulation," he said. "It can be the sound of screams or the visual -- something comes out of nowhere into the face, like a house of horror."
Music is also important, like the pulsating theme of the movie, "Jaws," as the white shark leaps out of the water.
Sometimes the sensation is tactile, when walking through an unstable platform in a fun house.
Roller coasters are the ultimate thrill ride. "Where else are you expected to throw your hands in the air and scream at the top of your lungs?" Farley asked.
"The intensity factor is important," he said. "On thrill rides, they really jerk a person around. They rotate the body and change the G force and people are screaming. You don't know what's going to happen next."
Novelty and contradiction is also a factor in fear -- a clown who kills or a child who is a monster.
Movies and books that exploit the most basic of human fears come dangerously close to reality. And experiencing that horror as a child can be a dress rehearsal for facing fear in the adult world.
"We have a lot of reason to be fearful in the world," said Farley.
"How could Jeffrey Dahmer kill and eat those boys and store their body parts in the refrigerator?" he asked. "Gadhafi is dead today, but in the early days of his dictatorship he hung protesters from lampposts."
Children have an uncanny attraction to frightening stories and psychologists say they project their fears and come to terms with them through stories.
Some of the most popular children's fiction involves ghost, vampires and skeletons. Harry Potter enthralls readers with witches and warlocks. R.L. Stine's original "Goosebumps" series -- "Welcome to Camp Nightmare" and the Abominable Snowman of Pasadena" has entertained teens for decades.
Some of the original Grimm Brothers' fairy tales, culled from folk stories that had been recited over generations, were gruesome, including rapes, incest, child murder and incessant bullying, according to the trivia website, The List Universe.
In "Snow White," the queen asks for the young maiden's liver and lungs, which she intends to serve up for dinner. In the end the wicked queen dances in red hot iron shoes.
The original "Sleeping Beauty" is bitten and then raped by the king (not kissed by a prince), and she gives birth to his two children in her sleep. One of them sucks off the flax that has kept the princess asleep for 100 years, waking her up.
The "Pied Piper" actually entices the village children to follow him to a river, where they all drown. And the step-sisters of "Cinderella" cut off parts of their own feet to fit into the glass slipper.
"Fairytales are a path to dealing with fear, to figure out how it works, what it is and recognizing it," he said. "Pulling your head out of the sand when you are surrounded by horror or fearsome things has a high survival value."
The same may be said of horror movies -- the terror that reflects life's real fears is the worst. One filmgoer said the 2011 film "Contagion," about a lethal pandemic, was particularly frightening.
"It's not the horror movies that scare me," she said. "It's movies about things that seem like they actually could happen. As a germ-a-phone, that was terrifying."
Others have given up the genre forever.
"I have a theory," said Wheeze Carlson, a 59-year-old from Michigan who was raped as a girl. "Only people that have never experienced true fear and terror like that stuff. The rest of us never want to ever revisit that emotion again."
And even those like Michele Sinesky who crave horror movies, have their limits.
"I avoid human monsters at all costs," she said. "And I hate slasher movies."