We’ve all had those stomach-drops-to-the-floor moments and swear we will never, ever watch another scary movie.

Then we do it again.

What it is about bone-chilling screams that people find so addictive?

Fear can be an “adrenaline rush,” said Craig Dominey, founder of The Moonlit Road, a website (http://themoonlitroad.com/) and podcast of Southern ghost stories and other folk tales. “It makes you feel alive.”

As a boy, Dominey remembers camping trips in the woods and hearing stories about a maniac lurking nearby. You know the type: An escapee from the asylum who somehow got his hands on a hockey mask and a machete and then headed straight for the summer camp.

“There’s the sound of the fire and branches snapping,” he said. ”You try to sleep at night, but you can’t.”

Whether it’s watching a scary movie, reading a horror book, riding a roller coaster or cave diving, there’s a certain level of excitement associated with a fear of the unknown.

Fear and excitement go together like those creepy twins in “The Shining.”

“When you’re excited your heart races and your breathing picks up,” said Stanley Hibbs, a Dunwoody psychologist and author of “Anxiety Gone: The Three C’s of Anxiety Recovery.” “Your body does the same thing when you’re scared. Some people really like the physical sensation.”

It’s also emotional.

“The idea of being able to say ‘I made it, though’ provides a great euphoric sense of relief at the end,” Atlanta psychologist Jennifer Kelly said.

Ben Armstrong is sort of a merchant of fright. As a co-owner of the Netherworld Haunted House, he draws crowds willing to pay to be spooked. This year, Netherworld is expecting 50,000 visitors to its Norcross location through Nov. 3.

Armstrong points out that Netherworld serves a positive purpose because the fear can provide relief from the stress of work, traffic or everyday life.

“You just want to scream or you can laugh,” which is a related reaction, said Armstrong, who might turn up some days as a deranged old man in Netherworld. “When you’re in danger, just for moment, there’s an adrenaline surge. It’s just like being on a roller coaster that is plunging.”

It helps to remember that it’s all in the name of fun.

“There’s a lot of excitement, but you know it’s safe,” Armstrong said. “You know in the end you’ll be OK.”

What leaves some people feeling ill, provides chills and thrills for people like Chip Sieczko.

If Sieczko is in a roller coaster, the whiter his knuckles get, the more he likes it.

“I’m not necessarily looking to get scared, but I know if I get scared it will get my heart racing and my adrenaline going,” said Sieczko, a tech support worker and a regional assistant for American Coaster Enthusiasts.

Sieczko, though, gets a bigger scare from visiting places like Netherworld and Atlanta Zombie Apocalypse.

“There’s a lot of power in a pitch black room filled with fog and the unknown around every corner,” he said.

Fear even has tourism value, with Atlanta taking advantage of its newfound position as the center of the zombie universe.

The Big Zombie Tour is the most popular attraction at Atlanta Movie Tours, drawing the type of people who think real living involves rubbing elbows with the undead. The $45 tour travels to sites where scenes from“The Walking Dead,” “Zombieland” and “Teen Wolf” were shot.

“People have this fascination with Halloween and things that go bump in the night,” Atlanta Movie Tours President Patti Davis said. “I think it stems from being a kid and your parents threw you up in the air. That was pretty darn scary, but you wanted to do it again. People love to be scared.”