Transcript for What Happens to Our Brains When We Get Scared
Test Halloween -- what leaps to mind? For me, candy. Hershey kisses, Reese's cup, zero candy bar fella, just saying. If you chose trick or treat you're not alone. Americans are obsessed with creeping themselves out. Unlike sugar, scaring yourself could be good for you. Tonight our self-proclaimed scardy Katnik watt is going in for the thrill. Reporter: Scarehouse, Pittsburgh, Pennsylvania. A haunted house, Halloween attraction. Right? Wrong, very wrong. Deep in the basement two scientists from the university of Pittsburgh -- Let's get this over with. Nice to see you. Reporter: Are analyzing fear. Why do we flock to ghostly movies like "Poltergeist"? To zombie flicks like "Night of the living dead"? Why do we go to haunted houses? People go to a haunted house and come out feeling wonderful, they feel terrific. We want to ask why. Reporter: We will spend $7 billion on Halloween this year alone, candy overdose aside it might be doing us good. Okay, first some pre-scarehouse markers. Is this an elaborate joke? Reporter: How do I react cold to disturbing pictures? The cool parts of this brain scan show that I'm not relaxed. When I hear loud noises, even with the comfort of holding one of the scientist's hand, also not happy. I am a person prone to a little anxiety. But if they're right when I come out of the scarehouse I might be a changed man. This is not what I signed up for. Reporter: I'm wired with a heart monitor and electrodes on my fingers to measure sweatiness. I'm going in. This way! Aahhh! No! Bloody hell! Reporter: First of all, I react with a scream so strong I accidentally tear off my finger electrode. I'm not sure it survived or is going to take good Readings. We're looking at whether or not there are any differences when I was holding his hand during the startle. Reporter: Margy Kerr, as well as helping design this place, wrote a book about fear aptly named "Scream." Though it's to our advantage to jump, have a response. Because that's going to aid in our survival. To scream? To frighten the thing off? To alert others. To appear more scary ourselves so when we scream, our face takes on a more contorted expression, which can be scary. Aahhh! Reporter: We look scary because we're scared in a haunted house or home on the couch watching "The walking dead." We expect something to be a human and then it starts not acting like a human. That is a violation. Something different than what we expected. And we freak out? Yeah. Fear is largely a result of basically disruptions of our prediction systems. Reporter: Prediction systems can come into play with clowns. They are supposed to look happy and they have these painted-on smiles and very exaggerated expressions. Yet their eyes and mouth aren't Reading the same. Reporter: The guy playing the clown at a kids' party isn't smiling with his eyes and that subconsciously freaks us out. Why are we scared of ghosts? Ghosts are scary for lots of reasons. There's of course the fear of our own mortality that ghosts bring to mind. The dark. And the dark, we have no control. Anything could attack us without our knowledge. It's harder to locate our body in space. We lose all sense of where we are. Reporter: But yet many of us seek fear out. The first time I came to scarehouse was because I so desperately wanted to escape the stress of writing my dissertat dissertation. There's something that's been woven into our DNA that wants to go out and see new things, explore new areas. And to challenge ourselves. Reporter: In the modern world we get fewer chances of that. For many Americans, life is pretty structured. Too boring? Yes. Reporter: There isn't a lion at the watering hole to scare souse we seek out fear in books, movie houses, scarehouses. This might be good for us. When we're scared our thinking brain is taking a break. All the worry and the concern, it gets pushed to the side because our body wants to prioritize things that are going to help us survive. Reporter: I'm out. Time for the post-match analysis. I am subjected to the same sounds that previously made me jump. The startle, whether or not you were holding Margy's hand, was very high gamma. I didn't flinch at all with the noises? Yep. Less emotional response to the bad pictures. Reporter: Here's my brain when I saw those distressing pictures before. And after. Those warmer areas proving I'm much, much less agitated. You could be having an endorphin response. So it's sort of like the runner's high has now taken over, your brain is flooded with stress hormone and so things that would be stressful just don't register as much. Reporter: Medical science might one day use something like this to treat depression. Thinking about the negative thing, I couldn't hold the negative thought. When you go through a scary experience, it seems to recalibrate you. Reporter: The scarehouse was so bad that everything else pales into insignificantance. We just don't sweat the other stuff. I'm nick watt for "Nightline" in Pittsburgh. Next, it's almost here.
This transcript has been automatically generated and may not be 100% accurate.