Losing hurts about twice as much as winning feels good
In a 1992 study, Daniel Kahneman and Amos Tversky put a number on a very human quirk: losses sting roughly 2.25 times more than equal gains please. That lopsided feeling, called loss aversion, helped build behavioural economics, a field that studies how real people depart from the perfectly rational calculators of textbook theory.
Psychology was once part of economics. Adam Smith wrote in The Theory of Moral Sentiments about ideas close to loss aversion, and Jeremy Bentham saw utility as a psychological quantity. But in the early twentieth century economists pushed psychology out, distrusting a young discipline and fearing it would erode the mathematics. In its place they put homo economicus, a purely rational, self-interested decision maker.
The comeback rode on the cognitive revolution of the 1960s, when psychologists began treating the brain as an information processor. Herbert Simon offered bounded rationality: people are limited by time, brainpower and the difficulty of the problem, so they take shortcuts and settle for good enough. He compared it to scissors, with one blade our mental limits and the other the structure of the world around us. In 1979 Kahneman and Tversky published prospect theory, showing that people judge outcomes as gains or losses from a reference point, overweight small probabilities and underweight large ones, and change their answers when the same choice is framed as avoiding a loss. Kahneman won the Nobel prize in 2002.
Kahneman's later book, Thinking, Fast and Slow, split the mind into a quick automatic mode driven by shortcuts and a slower, effortful one, and traced biases such as hindsight and confirmation bias to the fast mode.
The ideas went into policy with Nudge, published in 2008 by Richard Thaler and Cass Sunstein. They argued that choice architects can steer behaviour without coercion, a stance they called libertarian paternalism, for instance by placing healthier food at eye level. Critics counter that redesigning choices this way could make people worse at deciding for themselves. A 2017 analysis by Niels Geiger found the field spread significantly after Kahneman and Tversky's work.
Source: Behavioral economics
