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When Does the Wisdom of the Crowds Turn Into the Madness of the Mob?

Crowdsourcsing the best answer works—but only under the right conditions. Without them, it can go horribly wrong.

ByKristen ClarkNOVA NextNOVA Next
Scientists are deciphering what makes a crowds useful and mobs single-minded.

Our collective belief in the wisdom of the crowds is everywhere these days. From the democracies that run our cities, states, and countries to sites like Kickstarter and Reddit where we vote on projects and ideas in the hopes that the best will be rise to the top. But as recent research suggests, there’s a fine line between crowd wisdom and mob madness.

This belief in the intelligence of the crowds has some hard numbers to back it up, going back at least a century. In 1907, Francis Galton analyzed the entries from a guessing competition at a farmer’s fair, in which villagers had guessed the weight of a butchered ox to win a prize. Although the nearly 800 guesses varied widely, the median came within nine pounds—and the average within a single pound—of the 1198 lb ox. “This result is, I think, more creditable to the trust-worthiness of a democratic judgment than might have been expected,” Galton wrote.

But one look at a riotous mob after a football game or the aftermath of Ireland’s housing bubble will remind you that, collectively, people can often be deeply unwise. So when can we expect a crowd to head us in the right direction, and when can’t we? Recently, researchers have begun to lay out a set of criteria for when to trust the masses.

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First, as evidenced by Galton’s ox story, democratic decision-making works well when each individual first arrives at his or her conclusion independently. It’s the moment that people start influencing each other beforehand that a crowd can run into trouble.

Philip Ball, writing for BBC Future, describes a 2011 study in which participants were asked to venture educated guesses about a certain quantity, such as the length of the Swiss-Italian border:

The researchers found that, as the amount of information participants were given about each others guesses increased, the range of their guesses got narrower, and the centre of this range could drift further from the true value. In other words, the groups were tending towards a consensus, to the detriment of accuracy.

This finding challenges a common view in management and politics that it is best to seek consensus in group decision making. What you can end up with instead is herding towards a relatively arbitrary position.

Independent decision making isn’t everything, though. A crowd’s diversity can be just as important. A 2004 study demonstrated that a group of individuals selected at random from a population outperformed a group of the same population’s best problem solvers, Ball reports. Individual experts may have been smart on their own, but on average, they were too similar, working from a narrower range of problem-solving approaches than the random group. That handicap more than offset their skill.

And a paper presented last month at a conference on collective intelligence takes this diversity idea one step further. Here’s Ball again:

Previous work might imply that you should add random individuals whose decisions are unrelated to those of existing group members. That would be good, but it’s better still to add individuals who aren’t simply independent thinkers but whose views are ‘negatively correlated’ – as different as possible – from the existing members. In other words, diversity trumps independence.

In the days of Facebook filter bubbles and carefully selected TV news pundits, it may now be harder than ever for our ideas to be truly independent, which could hobble our combined intelligence. But fortunately, these results show that we can still harness the wisdom of the crowds, we just need to invite a little dissent into our ranks.

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