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."