When we watch horror movies, our brains are hard at work, with lots of interconnected cross-talk between different regions to anticipate perceived threats and prepare to respond accordingly. This enhances our excitement while watching, according to scientists at the University of Turku in Finland. Researchers used an MRI to map the neural activity of subjects while the subjects watched horror movies. Their findings are described in a recent paper published in the journal NeuroImage.

According to co-author Matthew Hudson, now at the National College of Ireland in Dublin, the objective was to take a closer look at dynamic interactions in the brain during an intense emotional experience. Most prior studies on neural mechanisms have adopted a binary approach, in that the focus is on comparing two conditions. But this ignores the temporal dynamics between the two conditions—the continuous fear response.

Hudson told Ars, "We wanted to use a naturalistic stimuli and new ways to analyze neural data to try and understand exactly how the fear response changes over time" rather than simply comparing brain activity before and after a perceived threat. Horror movies provided the perfect fear-inducing stimulus.

To select which movies to use in the study, the Finnish team set up an online survey of 100 popular horror movies—selected based on their IMDb ratings—and 216 "filmoholics" evaluated the films based on how scary they were, their quality, and their popularity, as well as gathering data on how often people watched horror movies and what kinds of horror they found the scariest. (Psychological horror based on real events was rated scariest, along with unseen or implied threats.) The researchers also tallied the number of jump scares in each movie (courtesy of the wheresthejump database).

Ultimately, the team selected the 2010 film Insidious and The Conjuring 2 (2016) for the study. Per Hudson, both films had the same director (James Wan) and boasted a fairly high number of jump scares (24 and 22 respectively), plus not many people who took the survey had seen those films. That ensured that test subjects would be experiencing the films for the first time while in the scanner—compared to more famous films like Jaws (1975) or The Shining (1980). Participants rated their fear levels throughout both films.

The study focused on two types of fear: that creeping sense of foreboding in a spooky setting, with a growing sense that something is not quite right, and the instinctive jolting response we have to an unexpected sudden appearance of a monster or other threat (a jump scare). The team found that during the former scenarios, there are marked increases in brain activity in terms of visual and auditory perception. In the sudden shock scenarios, there was heightened brain activity in regions involved in processing emotion, evaluating threats, and making decisions, the better to respond rapidly to any perceived threats.

"I was surprised by the relative dominance of visual and auditory areas during the anxiety portions of the movie," said Hudson, since these were relatively quiet segments of the film, with a largely dark screen and little information. He surmised that this indicates the brain was trying to reduce the uncertainty involved by trying to gather as much available evidence as possible. The researchers also found a large degree of functional connectivity between different regions of the brain.

"My biggest surprise was just how global the fear response is," said Hudson. "There's constant information transfer between all of these systems. It makes sense that the whole brain is responsive to a potential threat, at the expense of anything else."

One person who definitely welcomes this neuroimaging study is Mathias Clasen of Aarhus University in Denmark, author of Why Horror Seduces, who specializes in studying our response to horror in books, film, video games, and other forms of entertainment. Clasen has examined the dominant personality traits of horror fans, and last year we reported on his investigation of two different fear-regulation strategies employed by subjects participating in a Danish haunted house: "adrenaline junkies" who lean into the fear, and "white-knucklers" who try to tamp down their fear.

Granted, the Finnish study wasn't focused specifically on horror—it was just using horror movies to study overlapping fear systems in the brain. But the findings dovetail with Clasen's own conclusions. "I love how they find that one brain network prompts vigilance—activation of sensory cortices—and sensitizes another network for action, the one that prompts fight-or-flight," Clasen told Ars.

“It’s just damned cool that somebody is finally using MRI to look at horror.”

"It's just damned cool that somebody is finally using MRI to look at horror," said Clasen. "Their findings confirm my core hypothesis: that horror exploits the evolved fear system. Finally, some solid empirical evidence. The classic horror-movie build-up makes us hypervigilant, all but trembling in anxious anticipation, and leads up to the jump scare, which produces a 'reactionary' startle response."

According to Hudson, this kind of study should be broadly applicable to other emotions, so future studies might focus on the brain's response to comedies or thrillers. Like Clasen, he is intrigued by why we enjoy horror movies so much. "It seems kind of counterintuitive," he said. "There seems to be an element of appeasing one's fears with respect to what we perceive to be overpowering, something we can't control that poses a threat to us."

Furthermore, many people who responded to the survey said they preferred to watch horror movies with other people, indicating that the genre may facilitate social interactions. "There's evidence to show that sharing a traumatic experience creates a sense of social bonding between people," said Hudson.

Exploring this question from a neurological perspective might involve looking at specific neurotransmitters such as the opioid system, which is involved in many different emotions, including fear. "I would like to see what opioid activity is occurring in the brain while watching a horror movie and whether these levels can distinguish between people who like horror movies and those who don't," Hudson said.

DOI: NeuroImage, 2020. 10.1016/j.neuroimage.2020.116522 (About DOIs).