It has been said of war that it consists of long stretches of boredom punctuated by brief periods of terror, and much the same can be said of trading. There are long stretches of time when little more than a trickle of business flows in through the sales desks, perhaps just enough to keep the restless traders occupied and to pay the bills. With no news of any importance coming across the wire, the market slows, the inertia feeding on itself until price movement grinds to a halt. Then, people on a trading floor disappear into their private lives: salespeople chat aimlessly with clients who have become friends, traders use the lull to pay bills, plan their next ski trip, or talk to headhunters, curious to know their value on the open market. Two traders, Logan, who trades mortgage-backed bonds, and Scott, who works down the aisle on the arbitrage...

But just before noon there comes the merest breath of change, rippling the surface of prices. Most people on the floor do not consciously notice it, but the slight tremor registers none the less. Maybe their breathing quickens, maybe muscles tense just a bit, maybe arterial blood pressure increases ever so slightly. And the sound of the floor shifts, from the quiet buzz of desultory conversation to a mildly excited chatter. A trading floor acts as a large parabolic reflector, and through the bodies of its thousand-odd traders and salespeople it gathers information from faraway places and registers early signals from events that have yet to happen. The head of the trading floor looks up from his papers and steps out of his office, surveying the floor like a hunting dog sniffing the air. An experienced manager can sense a change in the market, tell how the floor is doing, just from the sight and sound of it.

Logan stops in mid-throw and looks over his shoulder at the screens. Scott has already wheeled his chair back to his desk. Their monitors display thousands of prices and flowing news feeds, blinking and disappearing. To outsiders the vast matrix of numbers seems chaotic, overwhelming, and finding the significant bit of information in the mess of prices and irrelevant news items seems as impossible as picking out a single star in the Milky Way. But a good trader can do just that. Call it a hunch, call it gut feeling, call it tradecraft, but this morning Scott and Logan have sensed a kaleidoscopic shift in price patterns well before they can say why.

Moments after Scott and Logan have registered the change, they learn that one or two people on the Street have heard, or suspected, that the Federal Reserve will raise interest rates this afternoon. Such a decision announced to an unprepared financial community would send a tidal wave of volatility through the markets. As the news and its implications sink in, Wall Street, only a short while ago looking forward to calling it an early day, roils with activity. At hastily organised meetings traders consider the possible Fed moves. Having formed their views, traders then jostle to set their positions, some selling bonds in anticipation of a rate hike, which pushes the market down almost 2 per cent, others buying them at the new lower levels, convinced the market is oversold.

By 2:10, trading on the screen dwindles. The floor goes quiet. Across the world traders have placed their bets, and now wait. Scott and Logan have readied their positions and feel intellectually prepared. But the challenge they face is more than an intellectual puzzle. It is also a physical task, and to perform it successfully they require a lot more than cognitive skills. They also need fast reactions, and stamina enough to support their efforts for the hours ahead when volatility spikes.

Consequently Scott and Logan’s bodies, largely unbeknownst to them, have also prepared for the event. Their metabolism speeds up, ready to break down existing energy stores in liver, muscle and fat cells should the situation demand it. Breathing accelerates, drawing in more oxygen, and their heart rates speed up. Cells of the immune system take up position, like firefighters, at vulnerable points of their bodies, such as the skin, and stand ready to deal with injury and infection. And their nervous system, extending from brain down into the abdomen, has begun redistributing blood throughout their bodies, constricting blood flow to the gut, giving them the butterflies, and to the reproductive organs—since this is no time for sex—and shunting it to major muscle groups in the arms and thighs as well as to the lungs, heart and brain.

As the sheer potential for profit looms in their imaginations, Scott and Logan feel an unmistakable surge of energy as steroid hormones begin to turbo-charge the big engines of their bodies. These hormones take time to kick in, but once synthesised by their respective glands and injected into the bloodstream, they begin to change almost every detail of Scott and Logan’s body and brain – their metabolism, growth rate, lean-muscle mass, mood, cognitive performance, even the memories they recall. Steroids are powerful, dangerous chemicals, and for that reason their use is tightly regulated by law, by the medical profession, by the International Olympic Committee, and by the hypothalamus, the brain’s ‘drug enforcement agency’; for if steroid production is not turned off quickly it can transform us, body and mind.

From the moment the rumour first spread, and over the past couple of hours, Scott and Logan’s testosterone levels have been steadily climbing. This steroid hormone, naturally produced by the testes, primes them for the challenge ahead, just as it does athletes preparing to compete and animals steeling for a fight. Rising levels of testosterone increase Scott and Logan’s haemoglobin, and consequently their blood’s capacity to carry oxygen; the testosterone also increases their state of confidence and, crucially, their appetite for risk. For Scott and Logan, this is a moment of transformation, what the French since the Middle Ages have called ‘the hour between dog and wolf.’

Another hormone, adrenalin, produced by the core of the adrenal glands located on top of the kidneys, surges into their blood. Adrenalin quickens physical reactions and speeds up the body’s metabolism, tapping into glucose deposits, mostly in the liver, and flushing them into the blood so that Scott and Logan have back-up fuel supplies to support them in whatever trouble their testosterone gets them into. A third hormone, the steroid cortisol, commonly known as the stress hormone, trickles out of the rim of the adrenal glands and travels to the brain, where it stimulates the release of dopamine, a chemical operating along neural circuits known as the pleasure pathways. Normally stress is a nasty experience, but not at low levels. At low levels it thrills. A non-threatening stressor or challenge, like a sporting match, a fast drive or an exciting market, releases cortisol, and in combination with dopamine, one of the most addictive drugs known to the human brain, it delivers a narcotic hit, a rush, a flow that convinces traders there is no other job in the world.

Now, at 2:14, Scott and Logan lean into their screens, gaze steady, pupils dilated; heart rates drop to a slow idle; their breathing rhythmic and deep; muscles coiled; body and brain fused for the impending action. An expectant hush descends on global markets.

Reprinted from The Hour Between Dog and Wolf: Risk Taking, Gut Feelings and the Biology of Boom and Bust, by John Coates. Copyright © 2012 by John Coates. Reproduced by permission of Penguin Press.

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