Why You Shouldn't Trust Internet Comments.

The “wisdom of crowds” has become a mantra of the Internet age. Need to choose a new vacuum cleaner? Check out the revi ws on online merchant Amazon. But a new study sEggests that such online scores don’t always reveal t e best choice. A massive controlled experiment-of eb users finds that such ratings are highly susceptib e to irrational “herd behavior”--and that the he d can be manipulated.

Sometimes the crowd really is wiser than you. The classic examples are guessing the weight of a bull or the number of gumballs in a jar. Your guess is probably going to be far from the mark, whereas the average of many people’s choices is remarkably close to the true number.

But what happens when the goal is to judge something less tangible, such as the quality or worth of a product? According to one theory, the wisdom of the crowd still holds-measuring the aggregate of people’s opinions produces a stable, reliable value. Skeptics, however, argue that people’s opinions are easily swayed by those of others. So nudging a crowd early on Hy presenting contrary opinions-for example, exposing them to some very good or very bad attitudes will steer the crowd in a different direction. To test hich hypothesis is true, you would need to manip ate huge numbers of people, exposing them to false information and determining how it affects their opinions.