Your Body On: A Horror Movie

It's been a few weeks since costumes, fake blood and pumpkins showed up everywhere, and you know what that means: It's Halloween and horror movie season! Whether you're into supernatural scares, your standard slashers or something entirely different, having an intense (but not too intense) scare makes you feel good.

That reason? The flight or fight response. Horror films "hack" your body's natural risk response, triggering fear that feels fun because there's no real threat. Here's what's happening in your body as you watch.

Your body's flight or fight response is controlled by hormones, and you'll experience a few hormonal surges as you sit through the movie's first scares. The first is cortisol, a hormone responsible for stress. The second is adrenaline, a hormone that stimulates your brain.

Together, these hormones let your body know there's a threat nearby – even if it's not real – and set off the rollercoaster of fear and tension you'll experience during the film.

One of the first things you'll notice after a tense scene is your pounding heart. That's because the fight or flight response boosts your heart rate, making sure your muscles have all the oxygen they need to make a quick escape. You'll also start breathing more rapidly (again, oxygen). And your muscles will feel tense, and ready to jump into action at any time.

You'll also notice you become hyper-aware of your surroundings, so you can spot any enemies – even fictional ones – more easily. So when the filmmakers through in that inevitable jump scare, your brain tells your body to "GO" – and you'll probably gasp, shout out or jump.

A large part of the fight or flight response happens within your cardiovascular system, which means blood is diverted to some parts of your body over others. Your muscles, which could help you make a hasty getaway at any time, get more blood flow, while organs with less immediately important processes (like digestion) get less blood flow.

The result can be surprising: Your body temp will actually drop as you sit through a horror flick, especially in your extremities, like your hands and feet. When researchers used thermal imaging to record moviegoers, they found their core temperature dropped nearly 2 degrees Celsius – you can watch it happen here. So if you feel a cold, clammy hand brush up against you, it might just be your neighbor, chilled from the film.

Just like the film's protagonist, you'll feel like you went through it when the final credits roll. But if you love horror, there's a physiological reason: The fight or flight response also triggers a flood of dopamine, a "feel-good" compound. Dopamine is a crucial part of your brain's reward system – so when you experience the fight or flight response in a safe environment, it'll probably feel good.

So why do some people hate horror? Not everyone responds to the flight or fight response the same way, sociologist and "scare expert" Dr. Margee Kerr tells The Atlantic. If you had a scary childhood experience with clowns, for instance, sitting through the movie "IT" might not feel like a safe environment, and horror films that are too intense won't be fun.

All the more reason to pick up a range of horror movies to watch this season – and find a new fun new scary flick you love.