Why Your Hormones Run the Stock Market ====================================== Wall Street traders aren't rational calculators — they're biological organisms driven by testosterone and cortisol. John Coates explains why boom and bust cycles are built into our bodies, and what that means for anyone who takes risks. ---------------------------------------- SAM: Hey there, welcome back to 7 Minute Books. I'm Sam, and today we're diving into The Hour Between Dog and Wolf by John Coates. Sophie, I have to tell you, I read the title and thought it was a novel at first. SOPHIE: Right? It sounds like something mysterious. But it's actually a neuroscience book about Wall Street traders. And that title comes from a French phrase for that weird twilight moment when you can't tell if the shape in the distance is a friendly dog or a dangerous wolf. SAM: Yeah, and that's exactly the metaphor Coates uses for what happens inside traders' bodies when they're in the middle of high-stakes markets. The guy was a derivatives trader himself before he became a neuroscientist. SOPHIE: That's what makes this book so compelling. He lived it. He felt his heart racing and his palms sweating, and he realized something was going on beneath the surface of rational decision-making. SAM: And that disconnect bothered him so much he left finance to get a PhD in neuroscience. I mean, that's a pretty dramatic career pivot. SOPHIE: It is. But what he found is genuinely revolutionary. The human body isn't a neutral vessel for a rational mind. It's a finely tuned risk-assessment instrument built by millions of years of evolution. SAM: So when a trader sees a price drop, their body doesn't know they're in an air-conditioned office. It thinks they're being chased by a predator on the savanna. SOPHIE: Exactly. And the key players are two hormones, testosterone and cortisol. We all know them, but Coates shows they're the chemical architects of risk-taking behavior. SAM: And the pattern is both fascinating and terrifying. When a trader makes a successful bet, his testosterone rises. That makes him more confident, more willing to take risks, more likely to win again. SOPHIE: But here's the catch. The same hormone that creates success also creates the conditions for failure. As testosterone keeps rising, it starts impairing judgment. The trader becomes overconfident, reckless, blind to danger. SAM: Right. So eventually the market turns, and when it does, the crash isn't just financial. It's biological. Cortisol floods in, that's the stress hormone, and suddenly the trader is fearful, risk-averse, paralyzed. SOPHIE: And that creates a cycle. Coates calls it the biological cycle of boom and bust. During a bull market, rising prices trigger rising testosterone, which fuels more buying, which drives prices higher. It's a positive feedback loop. SAM: Until something breaks. A small loss triggers cortisol, traders get nervous, they sell, prices drop, more cortisol floods in, and suddenly the market's in free fall. The same biology that created the boom creates the bust. SOPHIE: And this completely undermines the efficient market hypothesis, which assumes traders are rational actors making calculated decisions based on all available information. SAM: Coates basically says that assumption is not just wrong but dangerously wrong. Markets aren't cold, calculating machines. They're hot, emotional, biological systems that amplify our deepest instincts. SOPHIE: And the implications go way beyond Wall Street. Entrepreneurs, athletes, soldiers, doctors, politicians, anyone who takes risks in uncertain environments is subject to the same hormonal forces. SAM: There's this concept he calls the 'winner effect,' which I found really striking. It was first observed in animals, when a male animal wins a fight, his testosterone rises, making him more likely to win the next fight. SOPHIE: But it creates a dangerous feedback loop. The same hormone that drives success eventually leads to overconfidence and failure. In the animal world, that's how alpha males get overthrown. In finance, that's how star traders blow up. SAM: So success literally changes your biology, and that change can be your undoing. That's humbling. SOPHIE: It is. But Coates doesn't just leave us in a place of biological determinism. He offers practical insights for managing these forces. SAM: For example, he says the financial industry is structured to amplify the worst effects. Traders are rewarded for short-term performance, which encourages excessive risk. They work in high-pressure environments that keep cortisol chronically elevated. SOPHIE: The whole system is designed to create addiction, not success. So Coates suggests reforms, compensate traders for consistency and risk management, not short-term gains. Create environments that allow recovery. Let hormones return to baseline. SAM: And for individuals, he recommends simple practices. Take breaks. Get enough sleep. Exercise regularly. Pay attention to your physical sensations. When you feel euphoric after a success, recognize that your judgment is impaired. SOPHIE: Which is not soft, New Age advice. It's hard, biological imperative. The book's deepest insight is that the boundary between body and mind isn't as clear as we think. We are physical beings who have developed rational thought, but that thought is always subject to biology. SAM: That really makes you question free will and responsibility, doesn't it? If our decisions are influenced by hormones we can't consciously control, how responsible are we? SOPHIE: Coates doesn't answer that directly, but he raises it in a way that forces humility. We need to be more compassionate toward ourselves and others when we fail. SAM: The book ends with a call for a new kind of economics that takes biology seriously. The 2008 financial crisis wasn't just a failure of regulation. It was a failure of understanding. The models assumed rational actors and ignored the biological forces. SOPHIE: So if we want to prevent future crises, we need systems that work with our biology, not against it. And honestly, if you want to go deeper into this, the whole library is over at 7minutebooks.com/app, with over 6,000 fiction and nonfiction titles you can read or listen to in any language, it's $2.99 a month, $9.99 a year, or $19.99 once for lifetime access. SAM: The takeaway for me is simple, we're always in that liminal space between dog and wolf, between rational and instinctual. The only wisdom is to know that and act accordingly. SOPHIE: And that's the hour between dog and wolf. We'll see you in the next one.