13 Things That Are Instinctively Scary To Humans (And Why)

A fear of heights is triggered when your inner ear feels an exaggerated gravitational pull and tells your other senses about it, alerting your body of the distance that exists between you and the ground. If said distance exceeds 30 feet or so, your body goes into panic mode as the eyes send visual signals to the brain.

The fear of heights is fascinating because while our body is wired to experience a shift in gravitational pull, we don't develop this fear at birth. A study conducted by scientists from the University of California, Berkley and Doshisha University in Kyoto managed to pinpoint the exact stage of development when this fear initially surfaces. According to them, this fear is developed after a baby begins to learn locomotor skills such as crawling or scooting. People only learn to be scared of heights when they begin to get a perception of space and movement. 

Ancient human beings were tree dwelling mammals who all too often became food for vicious snakes. Since the beginning of time, we've been afraid of snakes. Because of that, our eyes evolved to see colors more vividly - not so we could take beautiful rainbow pictures and post them on Instagram, but rather to avoid our snake predators. 

To prove this, a 2011 study showed children can find snakes faster than they can find flowers. In fact, it is our neural fear module that signals this ability. It's like having a built in snake alarm.

The fear of spiders is another built into our DNA thanks to our ancestors. Spiders posed a much bigger threat to humans in ancient times. Even a non-venomous bite could be lethal. Archeology suggests the ability to recognize and fear spiders resulted in more surviving offspring for our ancestors. Arachnophobia, or the fear of spiders, is often interlinked with the fear of snakes.

What's more interesting is that this fear disproportionately affects women. Female babies (some as young as just 11 months) are already four times more likely to fear spiders when compared to boy babies of the same age. This is likely due to the fact that during our hunter-gatherer days, if a woman were bit by a spider, her offspring would likely die without her. At a time when men were warriors and women were caretakers, a spider posed a much bigger threat to women and their children. 

Do you find yourself avoiding eye contact with that overly friendly passenger on the train? You might just be following an ancient instinct. Even infants instinctively look away when a pair of eyes they don't recognize looks at them. 

There's a reason we call the eyes the windows to the soul - they communicate a lot to other people. A pair of eyes emoting fear or sadness can trigger someone who sees them to react. When your brain picks up on emotive eyes - especially negative ones - it rapidly reacts to the possibility of danger by releasing a flood of aggressive hormones. Similarly, if we see someone looking at us, our brain is also triggered. Called scopophobia, the fear of being watched is an anxiety disorder that was first observed in 400 BCE. Humans are instinctively trying to evaluate other animals, including people. The idea of being watched can initiate fear, and affects women at a higher rate than men. 

Staring comes instinctively as well. Staring contests in the wild establish dominance, and humans are still reflexively trained to do this to other humans. 

Public speaking isn't just a fear of awkward high schoolers - it's a universal fear felt by people worldwide. Even people who aren't terrified of public speaking get some of the symptoms associated with the fear: butterflies in the stomach, sweating, have trouble sleeping the night before. And that's because the root of this fear is built into our DNA. 

This fear comes from our amygdala - the part of our brain that regulates emotion - reacting to the emotions displayed on each and every face in the audience, picking them apart to see which, if any, people pose a genuine threat. Specific configurations of facial features can be interpreted as threatening on a primitive level. The end result is crippling stage fright that most of us have been through at some point in our lives. Our instinct when faced with a sea of faces - especially if they're unfamiliar ones - is not to continue with the presentation, but rather to win what our mind has interpreted as a staring contest. That's why some people, when faced with the reality of public speaking, simply stare blankly into the crowd. For this reason, many people will picture something bizarre, like picturing the audience in their underwear, to overcome their glossophobia.