The week of October 25, 2015

This is your brain on horror films

By Cynthia McKelvey

Ever wonder how the maestros of horror film so adeptly tug at your worst fears? How do they keep you guessing, on the edge of your seat, until suddenly they give you a fright so big it sends you reeling?

Horror film directors may not realize it, but they’re relying on your brain’s natural wiring and chemistry to scare you and keep you coming back for more. Here’s how they do it.

The fear center activates

The amygdala, a small, almond-shaped area of your primal “lizard brain,” activates when you start to see scary imagery and hear creepy music. This part of your brain is also known as the fear center, and it kicks off a cascade of reactions in your body that prime your “flight or fight” response. Back in the day, the amygdala was activated when an actual predator was chasing you down the savannah. Now it’s activated when you see someone else chased down by a crazed man with a knife.

Release the cortisol

Once your amygdala starts working, it sends a signal to the adrenal glands atop your kidneys to release cortisol and epinephrine (aka adrenaline) to kick your body into high gear. Cortisol in particular is known as the “stress hormone”; it’s often linked to negative health when you’re constantly stressed. However, little bursts of it, like you’d experience watching a horror movie, can be quite good for your health.

Your heart starts pumping

The cortisol and epinephrine released from the flight-or-fight response work in concert to raise your heart rate, something you may have even noticed while sitting in the theater. In one study, scientists observed a group of 16 students watching The Texas Chain Saw Massacre for the first time. The students experienced an average increase in their heart rate by 14 beats per minute.

You get all sweaty

One way researchers measure emotional arousal (e.g., fear) is by looking at “skin conductance level,” or how much more you sweat during an emotional experience. When you get scared at a horror film, your body responds by increasing sweat secretions, making your skin more electrically conductive. A 2002 study found that people watching violent films experienced an increase in skin conductance when they saw graphic imagery.

You’re on guard

Ever wonder why so many horror movies use a burst of loud music to jolt you? The complex stimuli coming at you in a horror movie put you on edge, making you more likely to jump when the boogeyman finally pops out from his hiding spot. If that reveal comes with a loud sound, you may have literally jumped in your seat. This is called the “acoustic startle reflex.” It’s an involuntary start facilitated by a direct connection between the auditory processing area of your brain behind your ears and the amygdala mentioned earlier.

Dialed in on empathy

People who are very good at tuning into others’ emotions—i.e., people who are very empathetic—tend to avoid horror films. Some researchers believe this is because watching other people activates mirror neurons near the motor cortex of our brain. These researchers think mirror neurons may help us understand what other humans are doing in physical space by literally mirroring their movements on a map of our own body in the brain. Some evidence suggests people who are highly empathetic tend to have stronger activation of their mirror neurons when watching others. As you might expect, this experience can be very uncomfortable when seeing someone stabbed to death or dragged off into the darkness. However, researchers are not 100 percent positive that the mirror neuron system that exists in certain primates is present in humans as well—so take it with a grain of salt.

So whether or not you love horror movies, your reaction basically boils down to your wiring. In other words, we’re all like zombies controlled by the necromancers who are horror movie directors.

Illustration by J. Longo. Infographic by Max Fleishman.