The science of fear

The biology of being afraid and why this primal emotion is key for survival

(Image credit: Gisela Merkuur/Pixabay)

Home alone at night, you hear a loud crash. In an instant your heart starts racing, your muscles tense and your breath quickens. You are immediately alert, primed to fight or flee the source of the sound, which turns out to be a pile of books falling off that shelf you’ve been meaning to fix. But in that moment, your brain and body reacted as if you were in mortal danger.

Fear is one of our strongest and most primal emotions. It’s a big bad world out there, and being afraid of certain things protects us from potential danger to make sure we survive. Some evolutionary fears are hard-wired into our brains, but we can also develop new fears throughout our lives. As children we pick up on what makes our parents anxious, and we may also learn to fear certain things after negative experiences. Despite this, most of us are able to ignore our fears when it’s clear we aren’t in any immediate danger. We can enjoy the view from the top of a skyscraper rather than worry about falling, or turn out the lights safe in the knowledge that a predator won’t devour us in the night.

However, people with phobias have an excessive fear response that causes both physical and psychological distress. These extreme fears are divided into three different groups: agoraphobia, social phobia and specific phobias. Agoraphobia is generally referred to as the fear of open spaces, but it applies to the dread of any situation that is difficult– to escape from, or where help would not be available if something went wrong. Social phobia is the intense fear of interacting with people or performing, while specific phobias are the fear of a particular situation, activity or thing. These irrational fears can cause major disruptions to everyday life; somebody with acrophobia – an extreme fear of heights – may experience a panic attack simply trying to walk across a bridge. Depending on the trigger of their phobia, sufferers often go to great lengths to avoid situations that could affect them.

The cause of phobias is not always clear, but many cases are linked to experiencing or witnessing a traumatic event. For example, somebody may develop cynophobia – the fear of dogs – after being bitten. But whether the trigger is rational or irrational, as soon as the brain registers a scary stimulus, it activates the fight-or-flight response, thus preparing the body for action.

(Image credit: Dorothe/Pixabay)

Why do we scream?

Screaming is an innate reflex; it’s usually the first thing you do when you’re born. Although we might also scream from excitement or pleasure, it is most often a cry of distress. Researchers from New York University conducted an experiment using brain scans to see how our minds react to screams. When we listen to normal speech, what we hear is sent to the auditory cortex for processing so we can make sense of the sounds.

However, the study showed that when we hear a scream, the signals are sent straight to the amygdala to activate the brain’s fear response. The team also found that ‘ rougher’ screams – those that change volume more quickly – were the most distressing. The results show that screams are a very effective method of communication in humans. They not only help convey danger, but also help make those who hear them more alert.

Scared to death

It’s not just a figure of speech – it turns out you really can die of fright. The adrenaline released during the flight-or-response can be damaging in large amounts; although just watching some scary movies shouldn’t be enough to cause any harm! This stress hormone encourages the heart muscle to contract, but if your body releases too much adrenaline, your heart is unable to relax again. Adrenaline can also interfere with the cells that regulate your heart rhythm, causing it to beat abnormally, which could be lethal.

While not directly deadly, prolonged anxiety can have a significant negative impact on your health. The fight-or-flight response suppresses the immune system, leaving you vulnerable to illness. Going into survival mode on a regular basis can lead to digestive disorders as this non-essential system is repressed. Long-term stress can also lead to weight issues by disrupting the metabolism; elevated levels of cortisol can make the body less sensitive to insulin. Muscles that are constantly tense and ready for action can cause headaches, stiffness and neck pain. The list doesn’t end there; chronic anxiety has also been linked to cardiovascular problems, asthma and insomnia. Such a broad range of effects can be harmful to both physical and mental wellbeing.

This article was originally published in How It Works issue 87

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