Scott Britz, MD, PhD, an Associate Professor at Harvard Medical School, is a faculty member in the Joint Program in Nuclear Medicine. He was also trained in Pathology, performing over seventy autopsies, some under infectious disease precautions, although none as death-defying as the one performed in The Immortalist. His research interests are in the field of molecular imaging.
by Scott Britz
If it weren’t for the human amygdala, science-fiction and thriller writers would be out of a job. For the amygdala, a little almond-shaped piece of the limbic system, is the home page of fear in the human brain. You can’t be afraid without it. A patient with Urbach-Wiethe syndrome, a rare genetic disorder that destroys the amygdala, will watch with ho-hum curiosity while a tarantula climbs up his arm. Roller-coasters, knives, guns and misty cemeteries at midnight won’t even phase him.
Stimulating the amygdala isn’t the final test of science fiction as it is for horror writing. Science is that, of course. But fear is a big element of most sci-fi writing. Jules Verne might be an exception, but think of Dune or The War of the Worlds or 2001 and the chapters you remember best will be the ones that gripped you in the pit of your stomach and brought up a good crop of goose pimples.
When you hear a thud on your rooftop and look out to see that an alien spacecraft has landed on top of your house, the amygdala is activated by two different pathways. First, there’s a rapid “blind freakout” pathway emanating from a brain organ called the thalamus, which reacts to the general weirdness of sensations without trying to figure out what they are. The thud itself, for example. Or the ear-splitting whine of the ship’s bio-probe as it scans the neighborhood. This response lasts just long enough (an instant or two) for the second, slower pathway to kick in. This one gets routed through the hippocampus, the central directory for memories in the brain. Comparing the situation to our previous experiences lets us figure out what’s really happening, and to distinguish between a true alien invasion and a hot-air balloon that’s sprung a leak and simply fallen onto our house.
Once the amygdala is activated, it sends out signals to various centers of the brain, most importantly the hypothalamus, the home of the “fight-or-flight” response that prepares us to actually do something about whatever is scaring us. Actually, this would be better called the “fight-or-flight-or-freeze-and-wet-your-pants” response, since all three options are in nature’s instinctual repertoire. The hypothalamus acts in two ways. The faster of these is through the sympathetic nervous system, which shoots up our heart rate and blood pressure and dumps epinephrine (adrenalin) into our blood. The slower pathway is a chain reaction of hormones that wind up releasing about thirty or so chemicals stored in the cortex of the adrenal gland.
The result of all this is pretty familiar. The heart races. Breathing gets faster. Our digestive system shuts down. The skin turns pale as blood is shunted to muscle. Blood sugar levels shoot up. The pupils dilate to let in more light. Every muscle in the body tenses up, from the big ones along the spine (giving us shudders) to the tiny ones attached to hair follicles (raising up goose pimples). We sweat. We grimace. In extreme cases, we empty our bladder and bowels. The big point is that every one of these reactions helps the body focus on dealing with the threat at hand. If we have to fight, we’ll fight like wild animals. If we have to run, we’ll run faster than we ever thought possible. If we have to freeze, we’ll be statues.
The amygdala does more than just turn on fear. It can also turn it off. When fearful stimuli turn out to be harmless, it creates fear-extinction memories which it transfers to a part of the brain called the medial prefrontal cortex. These can suppress the slow hippocampal activation pathway, to keep us from unnecessarily going off our rocker in the future.
There weren’t any horror tales or thrillers in Aristotle’s day (imagine what Euripides would have done with an alien robot invasion on the stage), but his idea of catharsis is a good starting point for explaining why we’re willing to lay down good money to scare the poo-poo out of ourselves. Fear that we pay to experience is safe fear. But it runs us through the whole gamut of physiological responses, just as any scare does. When at last it drops us off gently back into the real world, we have a rebound of good feeling, knowing that the terror is over. We feel at peace. Cleansed, even. And a rush of endorphins gives us a natural high.
Techniques for evoking fear, then, are a must for every sci-fi writer’s toolkit. It pays to make a proper study of the subject. The easiest place to start is with yourself. What do you fear? Try to recollect those moments in your life that left you scared spitless. Keep a fear journal. Analyze those palpitations that come over you when you least expect them. What are your triggers? Remember: anything that scares you will scare someone else. Even if you’re not a writer, these can be eye-opening exercises.
Fear can be of something concrete or something invisible. Concrete is easy for a writer. All you have to do is describe your object of fear vividly enough—blood hemorrhaging from a severed artery, a strange seed pod found in the garage, maggots wiggling their way out of a leaky coffin—and your reader will invariably respond. Use all the senses. Use pain. In my book Code White, the heroine, Ali O’Day, has to endure having a brain probe shaped like an ice-pick driven through her eye socket. No anesthesia for her. Nor for the reader. I do everything I can to show what this would be like—the blood, the scraping of bone, and above all, lots of pain. Vivid doesn’t always mean detailed, however. Often a light brush has the most impact. Go back to Poe to see how much can be done with a wonderful economy of words.
Invisible objects of fear can be immensely powerful, too, but it’s essential to make the reader see them through their concrete effects. In my current book, The Immortalist, the most horrific thing is a virus that’s so small that a million of them could fit in a single red blood cell. So after a dramatic death scene I include a fairly graphic autopsy to show what the virus actually does to a human body. This give a face to what is faceless. Similarly, Code White is about a bomb planted in a hospital. If you work in a hospital as I do, that’s a pretty visceral creep-out. You can’t abandon your patients, so you’re stuck going on with your routine, knowing that you could be vaporized before you finish making that last stitch. The characters in the book have plenty of time to think about this. But the reader needs to see it. A small bomb has to go off, killing one person, which serves to make the really big bomb real. (There’s another maxim here. When it comes to evoking fear, one victim is more potent than a thousand.)
So, with all that said, what kinds of things scare us? I took a brief, unscientific survey. Top of the list: The unknown. That’s why children’s fears seem so much stronger than adults’. So much more is unknown to them. It’s probably a component of every other fear. As for the rest, here’s a list, in no particular order (I think Stephen King has hit every one of these sometime or other): Spiders. Snakes. Cockroaches. People. Death. Mutilation. Paralysis. Pain. Heights. Flying. Driving. Tunnels. Bridges. Clowns. Nuclear war. Terrorist attacks. Crime. Being alone. Intimacy. Needles. Examinations. Public speaking. Rejection. Ghosts. Demons. And (quite seriously) God. The list is probably endless. But, in the interest of completeness, I invite you to reply by describing one of your own fears (unless, of course, blogging is also one of them). Or submit your favorite fear moment from the books or movies you like best. Who knows? You might give a science-fiction writer just the angle he needs to create a masterpiece.
I’ll conclude by pointing out that there really is a smell of fear. Scientists call it an “alarm pheromone,” and it’s well documented that some form of it exists in humans and probably all mammals and even in insects. The precise chemical in humans hasn’t yet been identified, although evidence suggests it may be linked to a compound called androstenedione. Bottom line: fear is contagious. From a literary point of view, it sets up the ultimate benchmark. When a story is so hair-raising that it scares the person sitting next to you—someone who’s not even reading it—you know you’ve found the mother of all thrillers.