The Critique of Homo Economicus

For more than a century, the dominant economic theory treated human beings as perfect calculating machines. Homo Economicus was the model: an agent with stable and transitive preferences who processes all available information, calculates the expected utility of each option, and chooses the one that maximizes their benefit.

This model was mathematically elegant. It allowed for equations, graphs, and predictions. It had one problem: it did not describe any real human being.

Richard Thaler discovered something classical economics said was impossible: simply owning something changes the value we assign to it. A mug you received just 5 minutes ago already "feels" more valuable to you than to someone who doesn't have one.

In the classic experiment, participants given mugs asked for an average of $7.12 to sell them (WTA, willingness to accept). Those without a mug offered an average of $2.87 to buy one (WTP, willingness to pay). The same object, twice the value, depending only on who "owns" it.

Why does this matter? Because according to classical economics, WTA and WTP should be equal. Whether you own something or not shouldn't change its objective value. But the brain doesn't work with objective values: it works with losses and gains relative to a reference point.

If humans were rational, the way an option is presented should not affect the decision. But it does. Deeply. Thaler and Kahneman demonstrated that framing changes choices even when the options are logically identical.

"90% survival rate" and "10% mortality rate" are mathematically identical. But patients, doctors, and jurors react radically differently to each framing. Whoever controls the frame controls the decision.

Thaler observed that people consistently promise themselves they’ll do in the future what they can’t manage in the present. You commit to starting the diet on Monday, saving next month, studying during vacation. Your future self is heroic. Your present self wants ice cream.

This happens because of the hyperbolic discounting: the brain discounts the value of future rewards disproportionately. R$100 now is worth more than R$110 tomorrow, but R$100 in 30 days and R$110 in 31 days seem equivalent. The time gap distorts our perception of value.

In "Predictably Irrational" (2008), Dan Ariely took the critique a step further: human errors are not only real, they are systematically predictable. They are not random noise. They are patterns that can be mapped, studied, and exploited (or mitigated).

In 2017, Richard Thaler received the Nobel Prize in Economics “for his contributions to behavioral economics.” It was formal recognition that economics needed real humans, not rational robots, in its models.

Thaler distinguished two types of agents in his models: Econs (the rational agents of classical theory) and Humans (how people actually behave). His book "Misbehaving" (2015) documents how the economics profession resisted for decades admitting that Humans don't behave like Econs.