Fright or Flight? The Science of How We React to Fear

By Gina Wynn

October in the United States ushers in cooler temperatures, fall colors, and a much-loved holiday, Halloween. People are fond of celebrating Halloween for many reasons. Kids look forward to trick-or-treating and binging on sacks of candy, while adults enjoy reliving their youth with decorating and costume parties.

But for some, the highlight of Halloween is the experience of being scared. Alternatively, plenty of people detest feeling afraid. Why do people have such opposing opinions about how they regard fear? The answer is both physiological and psychological.

From Fear to High Gear

When you experience fear, your body reacts physically. The part of your brain that processes emotions, the amygdala, sends a distress signal to your hypothalamus, the “command center” of the autonomic nervous system (ANS), according to the Harvard Medical School article "Understanding the stress response." The ANS is made up of the sympathetic and the parasympathetic nervous systems.

The hypothalamus then activates your sympathetic nervous system and your adrenal-cortical system. This triggers a series of physical reactions known as the fight-or-flight response. The howstuffworks article "How Fear Works" describes this process in more detail.

Both systems operate simultaneously to alert your body that you may be in danger. The sympathetic nervous system communicates the message through nerve pathways. The adrenal-cortical system initiates reactions through the blood stream.

When the adrenal-cortical system is activated, your pituitary gland secretes adrenocorticotropic hormone (ACTH). ACTH then triggers the release of around 30 different hormones into your body including epinephrine, norepinephrine, adrenaline, and dopamine. This flood of hormones causes your body to tense, speed up, and switch into action mode in case you need to run or defend yourself.

More specifically, your body reacts like this:

  • Heart rate and blood pressure increase
  • Pupils dilate to take in more light
  • Breathing gets faster as smooth muscles in your lungs relax for greater oxygen intake
  • Palms and armpits sweat
  • Veins in your skin constrict to send more blood to your muscles
  • Digestion and immune systems slow to conserve energy
  • Blood-glucose levels increase to boost energy level
  • Brain reduces focus on small tasks to concentrate on the threat 

Fear for Survival

These fight-or-flight responses have served the same purpose since the beginning of humankind, although some of the triggers may have changed. Early humans relied on the responses to ensure survival by enabling quick reactions when they encountered a dangerous animal, extreme weather, or an enemy.

People who heeded the warnings of fear and avoided threatening situations had a better chance of living to pass on their genes to offspring. Their offspring would also inherit the fear reaction, which would then help them navigate perilous times.

In her book Fear: A Cultural History, Joanna Bourke, PhD, professor, Birkbeck College in London, wrote about Charles Darwin’s research on fear and fight or flight. “Darwin concluded that our fear reflexes are guided by ancient circuits deep in the human brain.” she noted. “That everyone behaves in similar fashion shows only that we share a common evolutionary heritage.”

Fear for Fun

Some people see fear as more than a mechanism for survival. They may enjoy feeling afraid and experiencing the fight-or-flight reactions. That can explain why pop-up Halloween stores deck their showrooms with spider webs, body parts, and zombie babies. And cable TV stations feature 24-hour horror movie marathons. People flock to over-the-top haunted houses and theme parks — and pay good money ­— to be scared out of their wits.

According to scientists, people’s brains react differently to the fight-or-flight response to fear. When hormones like dopamine are released into the body, some people experience a high. Known as the “feel-good hormone,” dopamine is involved with feelings of happiness.

But dopamine is released at different levels for different people during frightening situations, according to David Zald, PhD, professor, Vanderbilt University. As reported in the article "Why Do Some Brains Enjoy Fear?" that appeared on The Atlantic website, his research showed that some people lack what he describes as “brakes” on dopamine release and re-uptake in their brains. This may explain why some people are excited by a thrill, while others may not enjoy it as much.

To really enjoy the sensation of fright, however, you have to know that the situation is actually safe when you experience the fight-or-flight response, according to Margee Kerr, PhD. A fear researcher and faculty lecturer at the University of Pittsburgh, Kerr was interviewed for the same article in The Atlantic. She says that when you’re making your way through a haunted house and a monster jumps out from around a corner, your brain has time to process that the threat is not real.

Psychology of Fear

Physical responses to the release of hormones also affect your psychological responses to fear. According to Glenn Sparks, PhD, professor and associate head, Brian Lamb School of Communication, Purdue University, the body’s excitation transfer process lets your brain catalog how you were feeling while you experienced the fight-or-flight reactions (increased heart rate, blood pressure, and respiration). His work was cited in the Psych Central article "Why Some People Love Horror Movies While Others Hate Them."

For example, if you had a great time laughing with friends while watching a horror movie, those emotions would have been intensified because of your physiological state prompted by fear. After the movie, you’d be more focused on the fun you had rather than the fear. And you’d want to come back for more, he said.

But if you had a negative experience, you may think negatively about the horror movie genre. If you were on a date that wasn’t going well or got into a car accident on the way home, your lingering fight-or-flight arousal would heighten your unpleasant emotions, said Dr. Sparks. You would associate horror films with unpleasant feelings.

Respect Your Fear Response

If you’re in a safe place on your couch watching a horror movie marathon or at a haunted house with people you trust, go ahead and enjoy the thrill. But if you don’t find fright entertaining, it’s OK to pass on these types of activities. And if your fear gets in the way of your daily routine and becomes debilitating, it’s important to seek professional help.

Whether you’re wired to love or loathe being scared, you’re not alone.