“Researchers have found that three types of situation signal threat and elicit a massive physiological stress response—those characterized by novelty, uncertainty and uncontrollability.”
Have you ever wondered why Wall Street traders seem to go from untouchable gods to total wrecks in the span of a few months? We always talk about markets, charts, and fundamentals — but what about the BODY? What about the hormones raging through these people as they make split-second decisions with millions on the line?
That’s exactly what John Coates digs into. And let me tell you, this book changed the way I think about risk, stress, and human performance — not just in trading, but in life.
The Trader’s Arc
Let’s talk about a story involving a financial manager who goes from seeing the trade that will let him print a crazy amount of money, to winning a huge trade, to losing everything, to becoming helplessly lost.
Then we couple this with exactly what is happening in the body as these events unfold. We start with rapid, laser-focused calculations in the brain and body involved in a winning trade.
We venture into an egotistical, testosterone-driven, risk-management trade that can make or break a trader’s winning streak, but ultimately resulted in a huge win.
Then we have a loss occur in the market, which causes stress to flood the body at manageable levels for an experienced trader. During moderate levels of stress, this will ignite intrigue and drive within an individual.
And ultimately, we delve into a state of learned helplessness and critical levels of stress as our trader undergoes a loss of extreme magnitude during the 2008–2009 financial crash.
Coates doesn’t just describe this arc with financial jargon. He takes you INSIDE the body — the cortisol spiking, the testosterone surging, the gut tightening — and shows you how biology is running the show behind every decision on the trading floor.
The Winner Effect
One of the most fascinating concepts in the book is what Coates calls the “winner effect.” When a trader makes a winning trade, testosterone levels rise. That elevated testosterone then increases confidence, sharpens focus, and pushes the trader to take MORE risk.
And here’s where it gets dangerous. If the wins keep coming, testosterone keeps climbing, and the trader enters a feedback loop where they feel INVINCIBLE. They start taking absurd risks because their biology is telling them they can’t lose.
Sound familiar? It should. This isn’t just about traders on Wall Street. Think about anyone on a hot streak — an entrepreneur who’s had three wins in a row, a gambler in Vegas, or even someone in a relationship who feels like they can do no wrong. That’s testosterone talking, not rational analysis.
Coates ran actual studies on trading floors in London, measuring hormone levels throughout the day. The data confirmed what he suspected — morning testosterone predicted afternoon risk-taking. Biology was literally driving financial markets.
Cortisol and the Crash
If testosterone is the fuel of the boom, cortisol is the poison of the bust. When losses pile up, cortisol floods the system. In small doses, it’s useful — it sharpens attention and keeps you alert. But when the losses don’t stop and uncertainty keeps mounting, cortisol goes chronic.
And chronic cortisol is devastating. It impairs memory, kills rational thinking, and pushes people into a state of learned helplessness — where they stop making decisions entirely. They freeze. They can’t act. They just watch the screen and pray.
This is exactly what happened during the 2008 financial crash. Traders who had been riding testosterone highs for years were suddenly drowning in cortisol. Their bodies physically couldn’t cope with the uncontrollable losses, and their brains essentially shut down.
The kicker? Most of them didn’t even realize what was happening. They thought they were making rational decisions the entire time. But their hormones had taken the wheel long before the crash started.
Mind and Body
The most important takeaway is the link between mind and body, body and mind, and how it cyclically learns and influences itself.
Patterns in situations will mitigate stress over time, until stress no longer occurs because the situation is reproducible. Yet, when the situation is continuously novel, stress will accumulate over time.
This is huge for anyone in a high-pressure field. It explains why experienced traders handle volatility better — their bodies have literally adapted to the stress. But throw them into a situation they’ve NEVER encountered? All bets are off. The 2008 crash was novel for everyone, and that’s why even the veterans crumbled.
Coates ties this back to evolutionary biology beautifully. Our fight-or-flight response was designed for immediate physical threats — a predator, a rival, a natural disaster. It was NOT designed for months of watching numbers go the wrong way on a screen. But the body doesn’t know the difference. A P&L statement dropping a million dollars triggers the same cortisol response as being chased by a lion.
Women on the Trading Floor
Finally, apparently women are great portfolio managers because they hold onto trades for a longer period of time, unlike men who get a thrill from trading continuously.
Coates suggests that a more diverse trading floor — specifically, more women and older men with lower baseline testosterone — would actually produce more stable markets. Not because women are “better” at trading, but because their hormonal profiles make them less susceptible to the testosterone-fueled feedback loops that create bubbles.
It’s one of the most provocative arguments in the book. Wall Street’s instability isn’t just a result of bad regulation or greedy individuals — it’s a biological consequence of filling trading floors with young men pumped full of testosterone. The system itself is designed to go haywire.
Final Thoughts
John Coates used to be a trader on Wall Street before becoming a neuroscientist at Cambridge. That combination — lived experience plus scientific rigor — is what makes this book exceptional. He’s not theorizing from an ivory tower. He LIVED this. He watched colleagues lose their minds during market crashes, and then he went and studied the biology behind it.
If you’re into behavioral psychology, neuroscience, or just understanding why humans are so incredibly irrational when money is involved, this is a must-read. It sits perfectly alongside books like Thinking, Fast and Slow and The Psychology of Money — but with a biological edge that neither of those books provides.
4/5 — pick it up from your library or grab it online. Your monkey-brain will thank you for the education.
Thanks for reading.
— Leonidas
