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How Risky Is It, Really?Why Our Fears Don't Always Match the Facts
By DAVID ROPEIK
McGraw-HillCopyright © 2010 The McGraw-Hill Companies, Inc.
All right reserved.
Chapter OneTHIS IS YOUR BRAIN ON FEAR
Brain; An apparatus with which we think we think. —AMBROSE BIERCE
In general we are least aware of what our minds do best. —MARVIN MINSKY, THE SOCIETY OF MIND
What's Your Risk Response?
Imagine that you are taking a walk in the woods. It's late in the afternoon. The path at your feet is dappled with light and shadow falling across narrow twisting tree roots. There is swampy ground on either side of the path.
Now imagine that, out of the corner of your eye, you notice that one of those long, thin, curvy lines at your feet just moved. It seemed to slither a little. Like a snake. Quick! What do you do!?
If you're like most people, you freeze, or scream, or jump back, or do something to protect yourself from the snake. You don't wait to figure out whether it really is a snake. You react instinctively, without thinking. The conscious awareness of your reaction seems to come after the reaction itself has already taken place. In fact, it does. By the time you become aware that you are afraid, your brain has already been hard at work, subconsciously perceiving that you might die, which triggers the Fight or Flight or Freeze response that will keep you alive. (This instinctive response to risk is more commonly known as the Fight or Flight response, but a lot of animals, including humans, Freeze at the presentation of a threat, so I've renamed it.) This automatic response sets off all sorts of physiological changes. Your heart speeds up. You breathe faster. Your blood vessels constrict in some areas and loosen up in others so the major muscles get extra blood and oxygen and energy. Your pupils dilate. Your digestive system gets shut down. You lose some of your peripheral vision, and the range of your hearing narrows. Without realizing it, you begin to make a facial expression of fear. All of these preconscious events happen in an instant! These are the first moments of the Risk Response, the first firings of a fantastic biological system that helps keep you alive.
THE AMYGDALA TO THE RESCUE: HARD-WIRED TO FEAR FIRST AND THINK SECOND
The cerebral cortex, the familiar outer layer of the brain where we do higher-order information processing like conscious thinking and reasoning, isn't even involved in this initial stage of our response to danger. Your brain's first reaction to potential danger happens subconsciously, in a section of specialized brain cells down near the brain stem, in the part of the brain known as the subcortex. The subcortex is the evolutionary part of the brain that was in place and protecting our ancestors long before modern humans evolved the cognitive cortex that gives us the power, as Ambrose Bierce said, to "think we think." It's an effective bit of adaptive neural design, set up more for speed and survival than for rational decision making. This is the first foundational truth about the human Risk Response: when it comes to perceiving and responding to danger, human brains are hard-wired to fear first, and think second.
Here is what actually happens in the first critical moments of a Risk Response. The raw visual data about that line on the ground speed from your eyes to a region in the brain called the thalamus, a group of unique cells deep in the middle of your brain that acts as a sort of relay station. The thalamus receives information from certain parts of the brain, or from the outside world via your external senses. It processes the information a bit—in the case of a snake, it quickly turns the raw optical information into a blurry line—then speeds that partially processed information on to other brain regions. This all happens in just a few thousandths of a second.
One of the areas to which the thalamus sends its data is the cognitive cortex, where we do our higher-order thinking and conscious decision making. But the thalamus also sends that picture of a blurry line to another area of the brain called the amygdala (pronounced ah-MIG-dahla), shown in Figure 1.1. This is the part of the brain where fear starts. The amygdala is the star of the show. It doesn't get a lot of ink, but this one-inch-long area of unique brain cells, shaped kind of like an almond, is absolutely vital for keeping you alive.
The Triple F Response: Fight, Flight, or Freeze
For the fear response, as with real estate, location really matters. The thalamus is right next to the amygdala, but the cortex is further away. So when the thalamus sends its blurry picture of the line to both areas, the signal gets to the nearer amygdala first. Some-how—science does not yet know how—the amygdala can recognize information in the signal that suggests danger. It immediately sends out the alarm to the parts of the brain that control the automatic responses we use to protect ourselves. This is the Fight or Flight or Freeze response, what I'll refer to as the Triple F response, the first instinctive things that our bodies do to protect us.
Meanwhile, even as you are already starting to react, the message from the thalamus about that blurry curvy line is still on its way to the thinking cortex. The information that could mean danger hasn't even gotten to the part of the brain where you think. But the amygdala does not wait for a rational risk analysis from the cognitive cortex. It has already sounded the alert, and before you've thought about whether it's a snake or a stick—before you are even consciously aware of the line on the ground—you startle, freeze, jump, or scream.
Finally, after the Triple F changes have started kicking in, the same visual information that the thalamus sent to the amygdala makes it to the cortex, which processes the data—simply put, it thinks things over—and sends its thoughtful interpretation of the information to a variety of areas in the brain, including the amygdala. But this new, more rational input arrives approximately 22 milliseconds after the amygdala has already received the first subcortical message from the thalamus and sent out the alert. The amygdala does not wait around to find out what the cortex "thinks." It sounds the alarm before the thinking, reasoning part of the brain has even had a chance to offer its opinion.
This is a great system for survival: fear first, think second. If the line on the ground is a snake, you're safe. If it's a stick, maybe you're a little embarrassed about freaking out about a stick. But you're still safe!
Fear over Reason
The work involved in discovering this subcortical fear pathway was done on rats in laboratories. (And it was done using auditory, not visual, triggers, so it followed circuits from the ears to the thalamus, not the eyes. However, additional work suggests that the same early alert wiring system exists for inputs from the other senses as well.) But one of the wonderful things about research into various aspects of the Risk Response is how many examples there are in the real world that confirm what we've learned in the lab. Consider the personal observation of one of the great thinkers of all time, Charles Darwin, who observed in himself the impossibility of being perfectly rational about risk.
Darwin wrote "... our reason telling us that there is no danger does not suffice. I may mention a trifling fact, illustrating this point, and which at the time amused me. I put my face close to the thick glass-plate in front of a puff-adder in the Zoological Gardens, with the firm determination of not starting back if the snake struck at me; but, as soon as the blow was struck, my resolution went for nothing, and I jumped a yard or two backwards with astonishing rapidity. My will and reason were powerless against the imagination of a danger which had never been experienced." (By permission of Oxford University Press.)
Of course, had Darwin been directly exposed to the puff adder and stood there rationally considering the risk long enough to give the snake a chance to strike, he might have become the first winner of the Darwin Awards, the humorous acknowledgment of those who proved by the really dumb ways they accidentally killed themselves or destroyed their procreative capacities that it's better for the species to have them out of the gene pool. Most of the acts that win Darwin Awards are the result of outstanding stupidity, but conscious reasoning itself can be a form of stupidity if it delays your response to a risk when milliseconds matter.
So it's good for our survival that this hair-trigger system is set to go off when the amygdala senses the slightest possibility of danger. But it's not just triggered by information from our external senses.
What's Your Risk Response?
After reading the following instructions, set the book aside for a bit. Okay, now take 30 seconds and recall in as much detail as possible a time in your life when you were really, truly, deeply afraid!
Welcome back. How did your recollecting go? Did you experience any sort of physical sensation along with your memory? Maybe a hint of sweaty palms? A quicker heartbeat, or perhaps some sort of feeling in your chest or your gut? A bit of a dry mouth? In the classes I teach and the lectures I give, about a third of the participants in this informal survey report such sensations. These are physical Triple F responses, bodily changes triggered by the amygdala reacting not to the external sight of a snake or sound of an explosion, but merely to a memory that came from inside your head! If you experienced any kind of physical sensation along with your memory just now, you experienced what Darwin did, "the imagination of a danger," yet you reacted with a bodily manifestation of a Triple F response. Deep beneath your conscious mind, your amygdala was ready to protect you. (Interestingly, it's only after your brain senses all the physical sensations produced by the Triple F response that the conscious feeling of fear begins. Being consciously afraid is one of the last things that happens in the initial stages of responding to risk!)
THE FEAR RESPONSE CONTINUES
Okay, now what? The alarm has been sounded. Your autonomic Triple F response is underway. Let's say you have temporarily stopped dead in your tracks. Now let's suppose that the curvy line is a snake, and that it is coiled and hissing and looks like it's going to strike. What is the biological Risk Response, part two? Is the amygdala done? Hardly.
Not only is it effective at getting things going quickly, but the amygdala and the systems to which it is connected continue to protect you in several other ways. First, the amygdala turns up the volume on its connections with the outside world. It prompts the release of a neurotransmitter, a chemical signaling agent in the brain, called acetylcholine. Acetylcholine makes nerve cells throughout the brain and the body more sensitive and readier to fire. So when the amygdala sends out an alarm, it makes all your senses more acute. In essence, part of the initial Triple F response is a message from the brain telling the senses, "We're under attack! Pay closer attention!"
So now your sensory focus on the snake is sharper. And not only are you better at picking up sensory information in the first place, but the amygdala accelerates the speed at which that information travels after it enters the brain. It signals special cells in the thalamus, the relay station described a little earlier, to relay things faster. The faster the thalamus can process information and send it on to the amygdala, the faster the amygdala can sound the alarm, or keep sounding the alarm if the risky situation continues. This helps keep the senses on heightened alert, and that, in turn, does more to expedite faster relay of sensory input through the thalamus to the amygdala! It's a great reinforcing feedback loop for survival. But the amazing amygdala is not done yet.
Fear and Memory
Do you remember what you were doing on November 21, 1963? How about September 10, 2001? You probably don't. But you probably do recall where you were when John Kennedy was assassinated on November 22, 1963, or on September 11, 2001, the day of the terrorist attacks on New York and Washington, D.C. (or, if you're British, where you were when you heard about the tube bombings on July 7, 2005, or if you're Spanish, where you were on March 11, 2004, when terrorists killed 191 and injured more than 1,800 in a series of train bombings). Those were powerfully emotional events, and the more emotional the nature of what you are experiencing, the more strongly that memory will be encoded in your brain, and the more readily it will be recalled, especially if the emotion is fear. This is another adaptive feature of the brain's risk-response system, a trait that helps us survive. If you make it through the first encounter with that snake, it's pretty handy for you to remember the trail and the location in as much detail as possible, so that you can avoid getting yourself in the same mess again.
And guess what empowers this hyper memory for fearful situations. Yup, that tiny clump of unique nerve cells down near the brain stem called the amygdala. Here's how. In addition to triggering that release of acetylcholine as part of the Triple F response, the amygdala also triggers a flood of the stress hormone norepinephrine into the brain. Norepinephrine increases the amygdala's ability to remember the event that started everything in the first place. It acts like a Marine drill sergeant shouting, "Remember this in case it happens again!" The next time you hit that trail, your amygdala will remember, and it will be more prepared to protect you.
Memories that are stored in the amygdala are called implicit. They are representations of things that happened that we cannot consciously recall. (Explicit memory is the kind that we can consciously recall, like the memory of that scary time you summoned up for our little experiment a while ago.) What good is a memory that you can't consciously recall? Consider the patient of French physician Dr. Edouard Claparede, a young woman who could not form new memories—or so it seemed. Every time Dr. Claparede met with her, he had to introduce himself again. She couldn't remember having met him previously. But on one of these occasions, Dr. Claparede hid a pin in the palm of his hand, and when he shook hands with his patient, he deliberately stuck her with the pin. She winced, but they continued with their conversation, then bid each other adieu. The next time Dr. Claparede met with his patient, she still didn't remember him. But she wouldn't shake his hand! Her ability to form new explicit memories of meeting the sicko doctor with the pin was still impaired, but her amygdala's ability to form new implicit memories of danger was there to protect her.
Explicit memory, the kind that you can consciously recall, is obviously important for self-protection as well. And the amygdala pitches in here too. Explicit memory is formed and recalled by the hippocampus, a part of the brain right next to the amygdala. Along with the release of acetylcholine and norepinephrine, a Triple F response prompts the release of stress hormones called glucocorticoids, which do the same thing to the hippocampus that norepinephrine does to the amygdala. They facilitate better formation and faster recall of memories, in this case explicit memories. This probably happened when you experienced that scary situation that I asked you to recall a while ago. The amygdala caused a flood of glucocorticoids to rush into the brain, some of which made it to your hippocampus and helped it do a better job of recalling memories of what had happened.
(This part of the fear memory process works only if the levels of stress hormones in the hippocampus don't get too high or stay elevated for too long. When the stress is too severe, or when it lasts longer than a few hours, the hormones have the opposite effect. Instead of helping the hippocampus, high levels of glucocorticoids impair the formation and recall of explicit memory, sometimes permanently. There will be much more on this when we talk about the negative impacts of stress in Chapter 5, "The Perception Gap.")
The amygdala's powerful influence on learning about danger isn't done yet. Another result of the Triple F response is the release of the neurotransmitter glutamate. The brain sends signals by squirting neurotransmitters from one nerve cell—we'll call it Cell 1— into a tiny space, a synapse, sometimes triggering responses in Cell 2 on the other side. Glutamate is an important neurotransmitter for memory. If Cell 1 squirts only a little glutamate into that synaptic space, Cell 2 has a sort of hohum response. Add a bit more glutamate, and you get a bit more response. But at some point, when enough glutamate is pounding on the door, Cell 2 doesn't just respond. It metaphorically screams, "Eureka!" and undergoes several important changes that sensitize it to that unique signal the next time it comes around. Cell 2 "learns." It remembers. So the next time you're exposed to that stimulus, the low level of glutamate that wasn't enough to trigger the Eureka response the first time around is now enough to do the trick. Cell 2 has learned. This is good for survival, because the second time you encounter that risk, Cell 2 doesn't need as much of a signal from Cell 1 to prompt the explicit memory that says, "Be afraid!" Where does the amygdala enter this process? It facilitates this learning by increasing the amount of glutamate squirting into the synapses of the hippocampus, that vital area for explicit memory.
Excerpted from How Risky Is It, Really? by DAVID ROPEIK Copyright © 2010 by The McGraw-Hill Companies, Inc.. Excerpted by permission of McGraw-Hill. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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