Richard Thaler's breakthrough was realizing that human behavior isn't just flawed, but predictably different from standard economic models. This predictability allows for the creation of models that can anticipate and account for systematic errors, turning the observation of mistakes into a useful, scientific discipline.

Economic theory is built on the flawed premise of a rational, economically-motivated individual. Financial historian Russell Napier argues this ignores psychology, sociology, and politics, making financial history a better guide for investors. The theory's mathematical edifice crumbles without this core assumption.

Work by Kahneman and Tversky shows how human psychology deviates from rational choice theory. However, the deeper issue isn't our failure to adhere to the model, but that the model itself is a terrible guide for making meaningful decisions. The goal should not be to become a better calculator.

Post-WWII, economists pursued mathematical rigor by modeling human behavior as perfectly rational (i.e., 'maximizing'). This was a convenient simplification for building models, not an accurate depiction of how people actually make decisions, which are often messy and imperfect.

Economics-based rational choice theory frames decisions as a calculation of "expected utility," multiplying value by probability. This analogizes complex life choices—from careers to partners—to casino bets, oversimplifying non-quantifiable factors and reducing judgment to mere calculation.

Daniel Kahneman and Amos Tversky developed their theories by studying their own cognitive biases. They created simple questions or "riddles" where they knew the logical answer but still felt an intuitive pull toward the wrong one. This self-reflective methodology allowed them to craft experiments that were compelling to non-psychologists like economists.

Contrary to popular belief, economists don't assume perfect rationality because they think people are flawless calculators. It's a simplifying assumption that makes models mathematically tractable. The goal is often to establish a theoretical benchmark, not to accurately describe psychological reality.

Nobel laureate Daniel Kahneman proved that 95% of human decisions are governed by "System 1"—an emotional, fast-thinking part of the brain. Marketers often craft rational messages (for "System 2") that fail because they don't appeal to System 1, which truly drives behavior.

For a period, a perverse norm developed in economics where the 'better' academic model was one whose theoretical agents were smarter and more rational. This created a competition to move further away from actual human behavior, valuing mathematical elegance and theoretical intelligence over practical, real-world applicability.