It's about midnight; my husband and I are returning to our bed and breakfast after a night out. A wall joins our room and the room next to ours with fake ivy-covered latticework at the top, too high to look through unless you've climbed a ladder. It's a little uncomfortable, but the other room is vacant for the night, so we settle in. Around 2 a.m., a noise startles me awake. It sounds like a rustling, someone shifting slightly bendable plastic back and forth. I look around for the source of the noise but don't see anything. Moonlight filters in through the window and onto the wall. And then I see it-a face, up at the latticework by the ceiling. It's a man, pulling aside the fake ivy, staring in from the other room, a huge grin on his face that's about to become hysterical laughter. His smile is twisted and angry and his eyes shimmer with anticipation. I try to scream, but all I can manage is a wheezy whisper. Not even close to waking up my husband. I try and try to scream but my vocal cords just never seem to catch a noise. My terror is real and palpable-until my husband shakes me awake, at home in our bed, out of the scene.
Luckily for my husband and I, that was just a dream. But the nightmare reflected something unique to me: When I'm truly scared, I can't make any noise at all. When others scream, I wheeze. When others pass out, I open my mouth and very quietly yell. My silence is just one reflexive action in a litany of responses to fear performed the world over-others include blushing, laughing, passing out, running, punching, crying, vomiting, and yes, urinating and defecating. So why does one person react to fear differently than another? Is the reaction itself a learned behavior or a neurological response?
Fear itself works as a chemical reaction in the brain and happens in two simultaneous ways through the limbic system-one quick and one long. With the quick way, your brain receives a scary stimulus and sends that information to the thalamus. The thalamus doesn't bother taking time to decide if the stimulus is a real danger or not; it immediately sends that information on to the amygdala, which then signals the hypothalamus to hit the fight-or-flight button. That's the you-got-scared-and-jumped part. At the same time, your brain is taking a longer path to determine if the stimulus is really a threat. The thalamus sends the initial input to the sensory cortex, which figures out the meaning behind the stimulus, and then passes the info to the hippocampus, which attempts to determine the context of the stimulus. Suppose that a face you thought you saw in the dark was just a creepy looking vase. The hippocampus would see that, and send the "no threat" signal to the amygdala, which tells the hypothalamus to cool it with the fight-or-flight.
Of course, during that time, you could have started violently puking out all your fear. Thanks, brain. Consider it as your thoughts catching up to your actions, just a little bit late.
As it turns out, that vomiting-or any of the other reactions people have to fear-are all part of the brain's subconscious risk assessment as it processes the scary stimuli. Instinctually, your brain will determine the most important thing it can do to help you release tension and cope with that fear, and then spark an action.
Vomiters, your brain is telling your body that it needs to feel better-and like with food poisoning or the flu, throwing up brings that relief. Laughter is a "don't look at me" response, telling others around you that there's no problem so they don't come over and join the thing making you afraid. Someone who cries when they're scared is releasing stress-causing hormones in those tears so they can calm down easier.
People who faint, I'm sorry to say that your brain is just trying too hard. This response is called vasovagal syncope. Your brain simultaneously activates and inhibits two branches of your autonomic nervous system, leading to a drop in blood pressure and heart rate, and the resulting dip in the blood supply to the brain causes fainting.
As for people who freeze like I do, it's actually a form of playing dead, a response to show whatever scared me that I'm not a threat because, whoops, I'm already dead. So it can leave me alone.
But why, then, does a fear of something like spiders remain a quick fright while someone else's might spiral into a full-blown anxiety disorder or phobia? According to NYU neuroscientist Joseph LeDoux, a biological and external mixture is at play. We are each born with our own unique sets of genes, and we each go through different experiences in our lives, and those things combined may create a phobic disorder. For example, I may just think spiders are gross-but maybe Johnny over there lived in a spider-infested apartment and woke up with spider bites, and his family history shows a recurrence of anxiety disorders. Johnny is more likely to develop that deeper terror because he's predisposed to it.
In this way, we're actually pretty closely related to animals, which experience fear in an incredibly similar way. It's a phenomenon called associative learning. We subconsciously correlate a fearful experience with some sort of visual cue, and then every time we see that visual cue, it triggers fear. So really, even though we have these big powerful brains, they sometimes can't do much about our subconscious fear processing. Like I said before, thanks a lot, brain.
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