(Describer) A roller coaster.

(narrator) For hundreds of years, we've been paying good money to scare ourselves. Why? What is happening to our brains on these rides that makes us keep strapping in, generation after generation? And how do roller coaster engineers make us feel like we might plummet to our death without, you know, actually plummeting to our death? Turns out, being scared might actually be good for you. -[dramatic synth music] -[person screams]

(Describer) The title appears: "Overview." A woman stands on a patio overlooking a valley. "Dr. Margee Kerr, Professor of Sociology, University of Pittsburgh, Author, 'Scream' and 'Ouch.'"

(speaker) We're basically shutting down our thinking brain, and feeling just that primal instinct of, "Oh my gosh, I'm gonna die."

(narrator) That's Dr. Margee Kerr. She wrote the book on fear. Literally.

(Margee) When we're on a thrill ride, our sympathetic nervous system, which is the system responsible for fight or flight mode, is basically fully activated. And a whole cascade of chemicals are released in our brain, throughout our body.

(narrator) Dr. Kerr spent over a decade researching fear. She's traveled the world putting herself in objectively terrifying situations to better understand it. Like this walk around the ledge of a 116-story tower. No hands. Nice!

(Describer) Margee dangles over the ledge.

(narrator) Hard pass. But one of her favorite ways to elicit fear quickly is on a roller coaster.

(Margee) I've been riding roller coasters for over 30 years, and I remember pretty much all of them.

(narrator) Part of that is that one of the chemicals released when you ride a coaster, dopamine, has a memory boosting effect.

(Margee) Anytime our body is in a heightened state of stress, whenever we're afraid, we're going to work really hard to encode every detail into our memory, because it's important that we remember the things that scare us, so that we can avoid them later.

(narrator) One thing that we all remember from amusement parks is the scream.

(Describer) Feet dash up a ramp.

(Margee) There are very few places that it's okay to scream at the top of your lungs. And it's too bad, because screaming can actually make you feel better.

[kids screaming]

Studies have shown that when we scream, we increase our range of vision, we have faster eye movements, and even a heightened sense of smell because we're breathing more rapidly through our nose.

(narrator) And having a yell is especially good fun when you know you're on a safe ride. Roller coasters have actually been around since the 17th century. These old timey coasters were lower tech, but significantly more thrilling without all the, you know, safety rigmarole that we have these days.

(Describer) A vintage sketch.

(Margee) The history of roller coasters can be traced all the way back to something called the Russian ice slides. They were constructed out of wood and then covered in ice. People would grab something and go sledding down it.

(Describer) A portrait.

(narrator) Apparently, Catherine the Great herself was a fan of the Russian ice slides. Adding to the excitement was the fact that you might actually perish on your ride. You might say it's a real... um, slippery slope. I'll see myself out. Luckily, these days you're far more likely to be struck by a bolt of lightning than to get injured on a roller coaster, and that's because of the meticulous work of roller coaster engineers like Donnelly Williams.

(Donnelly) Roller coasters and all attractions are very safe.

(narrator) That's Donnelly now, in Vancouver, Canada, where he designs and developed rides.

(Donnelly) The testing and the safety wrapped around that is the first thing and the last thing on every designer and engineer's mind.

(narrator) Donnelly designs rides that are shipped all over the world.

(Donnelly) We have rides in California and Orlando, Japan, China, Abu Dhabi, France, Dubai, and even Singapore.

(narrator) He's being a little modest. Donnelly and his team designed some of the best loved rides in the whole world, like the Incredible Hulk at Orlando Studios, Big Thunder Mountain at Disneyland, and Harry Potter and the Forbidden Journey. Donnelly and his colleagues are responsible for the control system.

(Donnelly) The control system tells the ride to go, tells the ride to stop. Is constantly checking to see the position of the ride. Are they going too fast? Are they going too slow? It's the brains of the ride.

(Describer) Donnelly checks wiring.

(narrator) Donnelly and his team have to plan for every kind of body that might be on a ride, and every kind of thing that body might do on the ride.

(Describer) He reviews plans.

(Donnelly) You have to make sure that you can keep people safe, even though they themselves may try to do something unsafe. We will do something called a hazard analysis, where we basically look at a ride, and think about every single way that a person could be hurt, and how can we mitigate that risk.

(Describer) A coaster rounds a curve.

(narrator) But your body doesn't know it's safe. At least, maybe not right away.

(Margee) Your body is trying to quickly assess in milliseconds if you're safe, or if you're really in danger. Your sympathetic nervous system is driving all of this big chemical reaction. And a big part of that is being driven by the amygdala. The amygdala is very deep inside the brain, and it's responsible for a lot of emotional regulation. The amygdala is working as kind of a control center. Let's push more chemicals out into the body, or let's bring it back and slow it down. Within a second, you are reminded that you're actually safe. The parasympathetic is coming in to just tamp down the threat response a little bit.

(narrator) The chemicals released when the parasympathetic takes over, endorphins like dopamine, serotonin, endocannabinoids and oxytocin. They all feel really good.

(Margee) And what's left on a thrill ride is that feeling of thrill and euphoria.

(narrator) But then there's the stomach drop. When you're plummeting down a hill or flipping a loop on a coaster, your stomach actually does move in your body. We kind of think of our body as one solid mass, but it's not that at all. The force of gravity keeps our organs in roughly the same place when we're in our day-to-day life, but during the drop of a roller coaster, our organs fall with the rest of us, and feel weightless. And that sensation is deeply unsettling. Why, you ask?

(Margee) Our construction of reality is based on a predictive system. We're constantly anticipating what's about to happen next, so that we can be prepared.

(Describer) A figure appears.

(narrator) One part of that system is the vestibular system, and it's located way down deep in our inner ear. The vestibular system supplies data on balance to inform these predictions so we stay upright.

(Margee) Thrill rides like roller coasters are disrupting this entire system, primarily through disrupting our proprioception, or where our body is in space. Roller coasters basically just confuse the hell out of us.

(narrator) You may have heard acceleration described in terms of G-force. That G is for gravity.

(Donnelly) The G-forces that are applied to the guests on all rides, is defined nationally by a standard ASTM.

(narrator) That's the American Society for Testing and Materials.

(Donnelly) The F24 committee on amusement rides and devices figure out what is too much or too little to apply to guests.

(narrator) Most people can handle between four and six Gs. Some other people, like fighter pilots, deal with nine Gs, but only for a few seconds tops. Sustained periods of G-force can pull blood away from the brain, inducing g-LOC, or gravity induced loss of consciousness. In other words, you pass out. Exciting, but not conducive to enjoying a ride.

(Donnelly) So our goal when designing rides is to help the guests to be scared and then overcome it. You can overcome little fears, and that can help you build up to big fears.

(Margee) When you choose to do something scary, when you choose to push yourself, you gain a sense of confidence that makes everyday challenges seem not as hard. The type of research that we're doing, it's not just for fun. We are aiming to use our findings to help improve treatments for things like social anxiety or general anxiety, and a whole range of phobias.

(narrator) So, there you go. Roller coasters. One part thrill, one part self-care.

(Describer) Credits appear. Host/Co-Writer: Joe Hanson, Ph.D. Producer/Editor: Mimi Schiffman Director of Photography: Will Strathmann, Chris Szabunia Executive Producer: Rachel Raney Credits continue. Produced by PBS North Carolina for PBS Digital Studios. Anne Ray Foundation. Thank you to Margaret A. Cargill Philanthropies for Supporting PBS. Accessibility provided by the US Department of Education. Logo: PBS.

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Accessibility provided by the U.S. Department of Education.

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