Why do some people love to feel scared?

Who first said, "Boo!"?

Was it some Fred who knew that Wilma jumped when he growled like a saber-toothed tiger? An early Crusader who liked to surprise the kids upon his return home? A sly Juliet creeping up behind Romeo as he stared at the balcony?

No one knows, although it's safe to say that there always have been those who hate being scared, those who love being scared and those who do the scaring. At no time of year is this difference more dramatic than at Halloween, when one person's gore-bedecked party attire is another's worst nightmare.

Touring a haunted house can invoke eye-rolls or shrieks, depending on what people expect to encounter, or have grown used to encountering, or whether they were talked into coming along against their better instincts.

So why do some people seek out sensations that are spooky or creepy or outright horrific, while others will jaywalk to avoid a spider web?

It all has to do with — bwahahaha — their brains.

Justin Boseck is a clinical neuropsychologist who long ago became fascinated with how brains work, and how different each brain is from another.

Adrenaline, of course, is one of the hormones that prompt our fight-or-flight response when faced with a hazard. But that response also is affected by how we perceive our environment at the moment, said Jenna Bemis, a licensed psychologist in Minneapolis. That's based on what we've learned to expect from our environment.

"If that interpretation is, 'This is pretend, this is exciting,' then it's fun," Bemis said. "If you interpret that adrenaline rush as, 'This makes me feel afraid, this is unpleasant,' you want to avoid it."

That's why some people can sit through a horror flick gleefully flinching, because they know they're in safe surroundings. But traversing the dark parking ramp back to their car makes them break into a cold sweat.

Expectations are key.

Bemis described a study in which individual participants got an injection of adrenaline, then were told to sit in a waiting room. "Those who were in a waiting room with a person acting euphorically ended up also feeling and acting more euphoric themselves," she said. "But those who were in a waiting room with a person acting agitated ended up feeling more agitated themselves. Each got the same substance, but what was happening in their surrounding environment changed their interpretation of what they were feeling in their bodies."

"We all have a saying that humans' biggest worry, what provokes the most anxiety, is speaking in front of an audience," Boseck said. "Then it's death."

Boseck, who practices in Minot, N.D., specializing in brain injury, said that while it's not possible to avoid death, there are ways of becoming less frightened of public speaking — and of anything else that's scary.

He described a "scaffolding approach," a practice in which you construct psychological supports that make something feel safer and more accessible. For example, a person might start by just sitting in, say, a departmental meeting. "This may induce anxiety, but nothing comes of it," he said.

The next time, you stand longer before taking your seat. Again, you may feel anxious, but again, nothing comes of it.

The next time, you might speak a bit, noting that the walls didn't come crashing down. Each time, you say a little more, building a framework of security until you don't think twice about speaking up.

Some fears may never be overcome. Some never should, if they warn of an actual threat.

But some fears are best simply avoided if the emotional response they provoke is too harrowing. Bemis remembered working at a veterans' hospital where some patients loved the annual Halloween haunted house "and others thought the idea of doing something like this for hobby or sport or fun was the worst idea in the world."

Still, there will always be those who court thrills, who love to feel an adrenaline rush, which explains the popularity of action movies and suspense novels, but also "things like amusement parks, Canterbury Park, car racing — anything that gets the adrenaline up," Bemis said, adding that such experiences could be the foundation of a great date.

"The adrenaline rush from action-adventure movies or horror movies can get paired with the excitement of the date," she said. "If a guy is perceived as the protector at the haunted house, a feeling of closeness can come from a biochemical perspective.

"The person who brought you on the date is remembered as sort of exciting."