The Hour Between Dog and Wolf: Risk-taking, Gut Feelings and the Biology of Boom and Bust. John Coates
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type of movement – the voluntary control of muscles and the learning of new behaviour. The neo-cortex did indeed give us reading, writing, philosophy and mathematics, but first it gave us the ability to learn movements we had never performed before, like making tools, throwing a spear, or riding a horse.
There was, however, another brain region which actually outgrew the neo-cortex and contributed to our physical prowess – the cerebellum (see fig. 3). The cerebellum occupies the lower part of the bulge that sticks out of the back of your head. It stores memories of how to do things, like ride a bike or play the flute, as well as programmes for rapid, automatic movements. But the cerebellum is an odd part of the brain, because it seems tacked on, almost like a small, separate brain. And in some sense it is, because the cerebellum acts like an operating system for the rest of the nervous system. It makes neural operations faster and more efficient, its contribution to the brain being much like that of an extra RAM chip added to a computer. The cerebellum plays this role most notably in the motor circuits of our nervous system, for it coordinates our physical actions, gives them precision and split-second timing. When the cerebellum is impaired, as it is when we are drunk, we can still move, but our actions become slow and uncoordinated. Intriguingly, the cerebellum also streamlines the performance of the neo-cortex itself. In fact, there is archaeological evidence indicating that modern humans may actually have had a smaller neo-cortex than the troll-like Neanderthals; but we had a larger cerebellum, and it provided us with what was effectively a more efficient operating system, and hence more brainpower.
The expanded cerebellum led to our unparalleled artistic and sporting achievements. It contributed as well to the expertise we rely on when we entrust ourselves to the hands of a surgeon. Today, when our body and brain embrace, when we apply our formidable intelligence to physical action, we produce movements that are like nothing else ever seen on earth. This is a uniquely human form of excellence, and it deserves as much highbrow recognition as the works of philosophy, literature and science that occupy our pantheons.
REVVING THE BRAIN
Movement needs energy, and that means the brain has to organise not only the movement itself, but also the support operations for the muscles. What are these operations? It turns out that they are not all that different from those of an internal combustion engine. The brain must organise the finding and ingesting of fuel, in our case food; it must mix the fuel with oxygen in order to burn it; it must regulate the flow of blood in order to deliver this fuel and oxygen to cells throughout the body; it must cool this engine before combustion causes it to overheat; and it must vent the carbon dioxide waste once the fuel is burned.
These simple facts of engineering mean that our thoughts are intimately tied to our physiology. Decisions are decisions to do something, so our thoughts come freighted with physical implications. They are accompanied by a rapid shift in our motor, metabolic and cardiovascular systems as these prepare for the movements that may ensue. Thinking about the options open to us at any given moment, scrolling through the possibilities, triggers a rapid series of somatic shifts. You can often see this in a person’s face as they think – eyes widening or squinting, pupils dilating, skin flushing or blanching, facial expressions as labile and fleeting as the weather. All thoughts involving choice of action involve a kaleidoscopic shift from one bodily state to another. Choice is a whole-body experience.
We are forcefully reminded of this fact whenever we contemplate the taking of risks, especially in the financial markets. When reading of the outbreak of war, for example, or watching stock prices crash, the information provokes a strong bodily response: you inhale a quick lungful of air, your stomach knots and muscles tense, your face flushes, you feel the thump, thump of a heart gearing up for action, and a thin sheen of sweat creeps across your skin. We are all so familiar with these physical effects that we take them for granted and lose sight of their significance. For the fact that information, mere letters on a page or prices on a screen, can provoke a strong bodily reaction, can even, should it create uncertainty and stress, make us physically ill, tells us something important about the way we are built. We do not regard information as a computer would, dispassionately; we react to it physically. Our body and brain rev up and down together. Indeed, it is upon this very simple piece of physiology that much of the entertainment industry is built: would we read novels or go to the movies if they did not take our bodies on a rollercoaster ride?
The point is this, and I cannot emphasise it enough: when faced by situations of novelty, uncertainty, opportunity or threat, you feel the things you do because of changes taking place in your body as it prepares for movement. Stress is a perfect illustration of this point. We tend to think that stress consists primarily of troubling thoughts, of being upset because something bad has happened or is going to happen to us, that it is a purely psychological state. But in fact the unpleasant and dangerous aspects of the stress response – the nervous stomach, the high blood pressure, the elevated glucose levels, the anxiety – should be understood as the gastro-intestinal, cardiovascular, metabolic and attentional preparation for impending physical effort. Even the gut feelings upon which traders and investors rely should be seen in this light: these are a lot more than mere hunches about what will happen next; they are changes taking place in the bodies of traders and investors as they prepare an appropriate physical response, be it fighting, running away, celebrating, or whimpering for relief. And because movement in times of emergency has to be lightning fast, these gut feelings are generated quickly, often faster than consciousness can keep up with, and are transmitted to parts of the brain of which we have only a dim and diffuse awareness.
CONTROLLING OUR INTERNAL WEATHER
For body and brain to be unified in this way, they must conduct a non-stop dialogue, a process, mentioned above, called homeostasis. Oxygen levels in the blood must be maintained within tight bands, and are kept so by a largely unconscious modulation of our breathing, as must heart rate and blood pressure. Body temperature too must be maintained within a degree or two of 37 degrees Celsius. Should it drop, say, below this band, the brain instructs our muscles to shiver and adrenal glands to raise our core temperature. Blood sugar levels too must be reported and then maintained within narrow bands, and should they fall, bringing on symptoms of low blood sugar, the brain promptly responds with a number of hormones, including adrenalin and glucagon, which liberate glucose stores for release into the blood. The amount of bodily signals being processed by the brain, coming as they do from almost every tissue, every muscle and organ, is voluminous.
Much of this bodily regulation is a job allotted to the oldest part of the brain, known appropriately as the reptile brain, and specifically to a part of it called the brain stem (see fig. 3). Sitting on top of the spine and looking like a small, gnarled fist, the brain stem controls many of the automatic reflexes of the body – breathing, blood pressure, heart rate, sweating, blinking, startle – plus the pattern generators that produce unthinking repetitive movements like chewing, swallowing, walking, etc. The brain stem acts as the life-support system of the body; other, more developed parts of the brain, ones responsible for, say, consciousness, can be damaged, leaving us ‘brain dead’, as they say, yet we can live on in a coma as along as the brain stem continues to operate. However, as animals evolved, the nervous circuitry linking their visceral organs such as the gut and the heart to the brain became more sophisticated. From amphibians and reptiles through mammals, primates and humans, the brain grew more complex, and with it came an expanded capacity for regulating the body.
An amphibian such as a frog cannot prevent the uncontrolled evaporation of water from its skin, so it must remain in or close to water at all times. Reptiles can retain water, and therefore can live in both water and desert. But they, like amphibians, are cold-blooded, and that means they depend on the sun and warm rocks for their heat, and become all but immobile in cool weather. Because they do not take responsibility for controlling their body temperature, amphibians and reptiles have relatively simple brains.
Mammals, on the other hand, took on far greater control of their bodies, and therefore needed more brainpower. Most notably, they began to control their internal temperature, a process called thermoregulation. Thermoregulation is metabolically expensive, requiring mammals to burn a lot of fuel to generate body heat, to shiver when cold and sweat when hot, and to grow fur in autumn and moult in the spring. An idling mammal burns about five to ten times the energy of an idling reptile, so it needs to store a lot more fuel. As a result mammals