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The Hour Between Dog and Wolf, in detail
The Hour Between Dog and Wolf is John Coates's argument that financial markets are driven partly by biology, and specifically by the hormonal systems — testosterone and cortisol in particular — that evolved to prepare the body for physical challenges and that now operate on traders making millisecond decisions. Coates, a neuroscientist at Cambridge who spent a decade as a derivatives trader on Wall Street, ran field studies on a trading floor in London and measured the correlation between morning testosterone levels and afternoon trading profits. The results were striking enough to reshape how he thought about the relationship between bodily state and financial decision-making.
The core finding is what Coates calls the winner effect: winning trades increase testosterone, which increases risk appetite and confidence, which increases the likelihood of more wins — up to a point. Beyond a threshold, elevated testosterone leads to over-confidence, excessive risk-taking, and eventually the kind of catastrophic losses that precede market crashes. The same feedback loop operates on the way down: losing trades spike cortisol, which increases anxiety and risk aversion beyond what the situation rationally warrants, producing the paralysis and flight that amplifies crashes.
Coates extends the argument beyond individual traders to the market as a whole. If thousands of traders share similar physiology and similar reward structures, their hormonal states will be correlated. A sustained bull market raises testosterone across the trading floor; a crash spikes cortisol. These shared biological states create the irrationality that efficient market theorists attribute to bad information processing but that Coates argues is better understood as a biological phenomenon — the market's body responding to perceived threat.
The book draws on evolutionary biology, endocrinology, and neuroscience alongside financial history and Coates's own trading experience. It is not primarily a policy book, though Coates does suggest that the dominance of young men in trading and the monotony of floor culture amplifies rather than dampens these hormonal dynamics. Regulators who want to understand market crashes, he argues, need to understand physiology as well as incentives.
The big ideas
- 1.
Testosterone levels in the morning predict trading profitability in the afternoon. This correlation suggests that bodily state — not just information processing — shapes financial decision-making.
- 2.
The winner effect: winning raises testosterone, which raises confidence and risk appetite, which increases the likelihood of more winning — until the testosterone spike produces overconfidence and catastrophic losses.
- 3.
Cortisol is the stress hormone. In sustained losing conditions, cortisol elevation produces excessive risk aversion that goes beyond rational reassessment: traders stop making decisions that have clear expected value.
