What is the science behind fear?

Story highlights

  • Humans are born with two fears, the fear of falling and the fear of loud noises
  • Most fears are learned fears
  • Fear can increase dopamine in thrill seekers

(CNN)"I'll huff, and I'll puff and blow your house down," calls out the deranged writer Jack Torrance, hunting down his wife and son, in Stanley Kubrick's classic 1980 horror movie, "The Shining." And as he takes a breath, he brings an axe down on the bathroom door and starts to hack away. At the same time you hear Shelly Duvall, who plays his wife, scream from the other side. Torrance, played by Jack Nicholson, splits enough of a hole in the door to push his head through. "Here's Johnny!"

It is one of the most heart pounding moments in cinema, and while some find watching the movie stressful, others will relish it watching it over and over again.
    Fear is an adaptive behavior that we have to help identify threats. It is an ability that has allowed us as humans to survive predators and natural disasters.

    Innate fears

    We are born with only two innate fears: the fear of falling and the fear of loud sounds.
    A 1960 study evaluated depth perception among 6- to14-month-old infants, as well as young animals. Researchers placed the subjects on a platform that had plexiglass just beyond its edge to it to see how many of the subjects would actually step over the "visual cliff." Most of the subjects -- both children and animals -- didn't go "over" and step out on to the plexiglass. The fear of falling is an instinct necessary for the survival of many species.
    When you hear loud sounds, you most likely will react with a fight or flight type response. It's called "your acoustic startle reflex," said Seth Norrholm, a translational neuroscientist at Emory University. Norrholm explained that if a sound is loud enough "you're going to duck down your head. Loud noises typically means startling. That circuitry is innate." It's a response we have, that signals something dangerous may be around the corner.

    Learned fears

    Most fear is learned. Spiders, snakes, the dark -- these are called natural fears, developed at a young age, influenced by our environment and culture. So a young child isn't automatically scared of spiders, but builds on cues from his parents. "You get evidence from your parents and your environment that you need to be scared of these things," said Norrholm.
    While the fear itself is learned, though, humans seem to be predisposed to fear certain things like spiders and snakes because of evolution. "Back in our ancestral age ... young children learned not to pick up snakes and spiders because they're venomous," said Norrholm.
    In fact, studies have found that when asked to pick out spiders and snakes from a collection of pictures, both preschoolers and adults react more quickly than when asked to pick out non-threatening items -- like flowers -- from the same collection. That's believed to happen because of the bias we have carried toward them throughout time.
    As we get older, fears are developed because of association. Norrholm compares it to a combat veteran who survives an encounter with an IED that was hidden in a shopping bag. If that vet is redeployed and sees another shopping bag, "he has a fight or flight response. Here, an association has been made between the cue and the fear outcome."
    It's the same exact response a child has to scary Halloween decorations. "It's about context," said Norrholm. A young child may not know that a skeleton is a scary, until his parents say over and over how skeleton decorations are spooky.

    How does the brain process fear?

    When presented with something that scares you, your brain reacts with its fight or flight response. For example, if you see a snake while hiking, there are two roadways for your brain, said Norrholm.
    First is the low road that represents your brains sensory systems in the brain's amygdala. It's "what you see, smell, hear," and signals to the brain that this is something to fear. It's the adrenaline response that tells your heart to beat faster and your body to sweat.
    Almost simultaneously, there's a high road reaction. "That goes through your higher cortical center in you brain. The high road says 'I've seen this kind of snake before, and I don't have to worry'," said Norrholm. Think of it as the reasoning response that overrides the low road.
    "There is some evidence to suggest that thrill-seeking is like anything pleasurable -- gambling, eating, -- it releases dopamine," said Norrholm. Dopamine is a neurotransmitter that helps control our brain's reward and pleasure centers. "We know that the more you reward something, the more that they do it," said Norrholm.
    And the more that thrill-seekers seek out the dangerous behavior, the better they are able to engage the cortical high road, and provide the rational context that the thrill-seeking behavior isn't dangerous. Extreme sports athletes are a great example of this: They continue their dangerous behavior because each time they do it, they survive, Norrholm said.
    There are some people who genuinely seem to enjoy being scared. "We know there are some basic individual differences in how people are wired," said Glenn Sparks, a communications professor at Purdue University. Sparks specializes in the cognitive and emotional impact of the media, particularly horror movies.
    "Some people are wired to seek out highly sensational experiences." When they are exposed to that kind of experience "they get the adrenaline rush," said Sparks. He likens those who enjoy watching horror movies to people who like riding roller coasters.
    And Sparks says thrill seeking seems to have a gender bias. "Men have been socialized not to show signs of distress, but to conquer it. For females it is much more acceptable to show signs of distress."
    Studies show we can overcome some of our fears by continued exposure to them. By constantly exposing ourselves to our fears, whether it extreme sports, horror movies, or snake and spiders, our tolerance for them will grow, said Sparks.
    But, remember, that being frightened isn't always a bad thing. In fact, it's been a survival mechanism for humans for millions of years.