In a now-classic experiment reported in 1974, the psychologists Amos Tversky and Daniel Kahneman asked participants to watch a wheel of fortune marked from 0 to 100. Unknown to the participants, the wheel had been fixed to stop at only two numbers, 10 or 65. After it stopped, each participant was asked whether the percentage of African nations in the United Nations was higher or lower than that number, and then to estimate the actual percentage.
The number on the wheel had no possible connection to the question, and the participants had just watched it being produced at random. Nevertheless, it shaped their answers. Those who had seen 10 gave a median estimate of 25 percent; those who had seen 65 gave a median of 45.
Tversky and Kahneman called this pattern anchoring. When people must estimate an uncertain quantity, they tend to start from whatever number is available and adjust away from it, but the adjustment usually stops too soon. The final estimate therefore stays closer to the starting point than the evidence justifies.
Later studies extended the finding well beyond the laboratory. In one, experienced real estate agents valued the same house differently depending on the listing price they had been shown, yet most of them denied that the listing price had played any part in their judgment. Findings of this kind have made anchoring one of the most widely cited effects in the study of decision-making.
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