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Information sharing undermines collective intelligence
Last reviewed: 30.06.2025
The wisdom of crowds is a statistical phenomenon: individual beliefs cancel each other out, merging hundreds or thousands of guesses into an uncannily accurate average answer. But in the experiment, the scientists told test participants about their colleagues’ guesses, and as a result, everything went awry. The collective wisdom was undermined by the fact that knowledge of others’ guesses narrowed the diversity of opinions. “Even moderate social influence can produce this effect,” emphasize the study’s authors, Jan Lorenz and Heiko Rahut of the Swiss Federal Institute of Technology.
The phenomenon was first described in 1907 by Francis Galton, who noticed that fairgoers were able to guess the weight of a bull. The phenomenon was made widely known by James Surowiecki's book The Wisdom of Crowds (2004).
As Surowiecki explained, collective wisdom only shows its power under a certain condition: people must have different opinions and come to them on their own. Without this, wisdom is impossible, as some market bubbles have shown. Computer simulations of the behavior of large groups of people also hint that a balance between the flow of information and the diversity of opinions is necessary for accurate prediction.
The Lorenz-Rahut experiment falls somewhere between big real-world events and theoretical research. They put 144 students in isolated booths and asked them to guess the population density of Switzerland, the length of its border with Italy, the number of new immigrants to Zurich, and the number of crimes committed in 2006. The subjects were given a small monetary reward based on the accuracy of their answers, and then asked again. Some students were told what their peers thought, while others were not.
Over time, the average responses of the independent subjects became increasingly accurate, but the responses of the students who were influenced did not. The researchers explain this in three ways: first, opinions became less diverse; second, the correct answers clustered at the periphery rather than in the center; and third and most important, the students became more confident in their guesses.
"Opinion polls and the media contribute greatly to the idea that society thinks more or less the same," the scientists write. Thus, the wisdom of the crowd, which is only an average of the spread of opinions, is perceived as evidence of unity. And then the businessmen and politicians who offer what everyone seems to need turn out to be of no use to anyone.