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Loss Aversion: Why Losing $100 Hurts Twice as Much as Gaining $100
Kahneman & Tversky 1979 — the paper that toppled rational choice theory
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Two Friends in a Jerusalem Cafeteria
In 1968, at the Hebrew University of Jerusalem, Daniel Kahneman, then 34, was giving a lecture when Amos Tversky, 31, posed a series of persistent questions. After the lecture, Kahneman sought out Tversky. For the next three decades, the two met daily in the cafeteria, engaging in conversations that challenged each other's hypotheses. Their central question was: "Do people truly make rational decisions?" In the 1970s, every economic model assumed this to be true. Kahneman and Tversky systematically dismantled these assumptions, one by one, through their experiments.
Irrationality in a Coin Toss
In Experiment 1, participants were asked to choose between "receiving a sure $80" and "a coin toss: $100 if heads, $0 if tails." Despite the latter having a lower expected value of $50, most people rejected it, opting for the certain $80 – demonstrating risk aversion. Experiment 2 presented a mirror image: a choice between "a sure loss of $80" and "a coin toss: a loss of $100 if tails, $0 if heads." The same individuals suddenly chose the latter, which carried the potential for a greater loss. This revealed a tendency to seek risk in the domain of losses. Decisions were completely reversed depending on whether the choice involved gains or losses, a phenomenon inexplicable by rational economic models.
Prospect Theory and Double the Pain
Kahneman and Tversky charted a value function, which appeared as an S-shaped curve. The segment representing gains was a gentle concave slope, while the segment for losses was a steep convex slope. The most crucial insight was that the gradient on the loss side was approximately twice as steep as on the gain side. This meant that the pain of losing the same $100 was roughly twice as intense as the pleasure of gaining it. This groundbreaking discovery initiated the new field of Behavioral Economics. The power of marketing slogans like "buy now or miss out," the tendency of stock investors to hold onto losing shares for too long, and the difficulty of making concessions in negotiations are all explained by loss aversion. When Kahneman received the Nobel Prize in 2002, he remarked, "This is thanks to Tversky."
Loss Through Chinese Characters
The Chinese character "失 (shī)" visually represents something falling from a hand (手), symbolizing the act of something once held slipping away. In the Xian Wen chapter of "The Analects," it states: "君子, 不憂不懼" – "A superior person is free from worries and fears." When Zigong inquired how this was possible, Confucius replied, "If, upon introspection, one finds no shame, what is there to worry about, what is there to fear?" Thus, "失" refers not to the loss of an external object, but to the disturbance of inner tranquility. Kahneman's measured "double the pain" does not reflect the intrinsic value of $100, but rather the psychological weight with which the Self (自我) was attached to that $100. If one is bound by public (公) concerns, there is little to lose; if bound by private (私) concerns, there is much to lose.
