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The wisdom of statistically manipulated crowds

The next time somebody tells you about a wisdom-of-crowds effect, make sure you ask them whether they're talking about a real crowd or a statistically enhanced crowd:


Even in its most basic expression, the wisdom-of-crowds effect seems to be exaggerated. In many cases, including the ones covered by the Swiss researchers, it's only by using a statistical trick that you can nudge a crowd's responses toward accuracy. By looking at the geometric mean rather than the simple arithmetic mean, the researchers performed the statistical equivalent of cosmetic surgery on the crowd: they snipped away those responses that didn't fit the theoretical wisdom-of-crowds effect that they wanted to display. As soon as you start massaging the answers of a crowd in a way that gives more weight to some answers and less weight to other answers, you're no longer dealing with a true crowd, a real writhing mass of humanity. You're dealing with a statistical fiction. You're dealing, in other words, not with the wisdom of crowds, but with the wisdom of statisticians.

People seem to have missed the main point of Lehrer's column, which is the more a crowd socializes, the less “wise” it becomes.

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Related: Jonah Lehrer's column in the WSJ, Peter Freed's blog post arguing that Lehrer misread the evidence, The paper in question.

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