The “wisdom of crowds” is the observation that groups of people often make better decisions collectively than even the smartest single member of the group. For example, a crowd of ordinary people at a county fair betting on the weight of an ox can, through the result of this simulated market, be more accurate than even trained cattle experts. Or a group of amateur chess players voting on what moves to make could beat a much more experienced player. Why do things like this happen?

One way of looking at it is that there are usually more ways to be wrong than ways to be right. Imagine a large group answering a difficult multiple-choice question, with options A, B, C, D, and E. Most people do not know that the correct answer is C. But of the 30% who know this, everyone will choose C. The remaining 70% of the crowd will have a mix of wrong answers and perhaps by accident the correct answer—some will have a hunch and other will just guess randomly. On average each choice from the 70% of the crowd who do not know answer will get about 14% each, which is a total of 44% for the correct answer versus 14% for each of the wrong answers. It can be even higher because people may be able to narrow down their choices to less than all five choices. The correct answer stands out even if only a minority of the crowd knows it.

Using market mechanisms allows people to use probabilistic knowledge and contribute to an answer even when they are not sure of the answer because there is meaningful information in hunches and intuitions.

Another reason crowds can be so smart is that individual members of the crowd often have pieces of information that no one else in the crowd has. No single member has all the pieces of the puzzle, but when crowds make decisions as a group, all the information from different members can be taken into account. For this to work, there needs to be some method for everyone in the crowd to communicate and integrate these disparate hints.

In the novel, ten-year-old Danielle recognizes the wisdom of crowds when she asks her Twitter followers a hard question about a pattern in the jazz pieces she plays at her Lincoln Center Concert. She guesses it will take 20 minutes to figure out that the time signatures use prime numbers instead of the usual powers of two, but the online crowd forms a correct consensus in just 15 minutes. Later, Danielle uses the wisdom of crowds when using her followers to solve problems and create positive change in places like Libya and China. You can harness the wisdom of crowds, too!

To get more familiar with how the wisdom of crowds works, take a look at this talk by James Surowiecki,¹ who literally wrote the book on it: The Wisdom of Crowds: Why the Many Are Smarter Than the Few and How Collective Wisdom Shapes Business, Economies, Societies and Nations (Doubleday, 2004).

Here are some areas where you can put these ideas into practice:

• Crowd-sourcing opinions. Danielle keeps in close communication with her millions of social media followers, and they give her important insights about what is going on in the world. In the same way, you can use social media to get answers that harness the wisdom of the online crowd.

Let’s say you hear conflicting stories about water pollution problems in Africa and want to learn the truth from people on the ground there. If you just asked a lot of people individually, you’d get many different answers, but no information from the crowd about which ones are more reliable. However, sites like Reddit fix this problem by giving people the ability to up-vote or down-vote answers they think are good or bad. Over time, these votes reflect the collective judgment of the crowd.

As a less serious example, when you read user reviews of products on Amazon, you’re using the wisdom of the crowd. Amazon lets people rate the reviews they read, and the software prominently displays the reviews that most people found useful. This mechanism gives you information that’s more reliable than any single expert review on its own.

Other ideas for seeking opinions that use the wisdom of the crowd include:

• Have your Facebook friends recommend books to read or movies to watch, and ask them to “Like” the other suggestions they think are good ones.
• When considering what colleges to apply to or jobs to seek, look for reviews or testimonials that many people have already up-voted, liked, or rated as helpful.
• If you’re curious about an interesting or difficult question in an academic subject or about the creative arts, ask for help under-standing it on Stack Exchange.² This website pools information from knowledgeable people, and the best answers to your question will get voted to the top.
• If you’re wondering how likely a major world event is, take a look at prediction markets (discussed further below), because they reward people for using good information and making accurate predictions.
• Collaborative problem-solving. Everyone has their own unique set of mental strengths and weaknesses, and their own base of knowledge and experiences. Solving hard problems often requires many different kinds of problem-solving abilities, and no single person has them all. Harnessing the wisdom of crowds can help solve problems that even top experts can’t figure out.

In biology, one important set of difficult problems concerns figuring out how proteins fold into different shapes. This is important for designing new medicines and curing disease. So scientists at the University of Washington created an online game called Foldit,³ which turns the process of figuring out protein folding into a fun puzzle. 57,000 players tackled these puzzles, using all their diverse problem-solving skills. The game gathered the insights they figured out, and the solutions from the players outperformed what individual experts or the software algorithms could do.

You can use the wisdom of crowds to solve problems in many ways, including:

• Collaborative engineering. If you’re working on an invention or trying to create something new—either as a physical device, or in computer programming—it can be a big help to get suggestions from a large group, such as on a specialized forum.⁴ Each poster will have their own skills and experiences and can comment on each other’s ideas. This is why software companies do beta testing. Large numbers of users talking with each other and the developers can find problems more effectively than a small number of experts.
• Networking. To make a difference in the world, you’ll often need to find a certain type of person to help you—maybe an expert who you can trust in a certain subject, or a person who’s mastered a certain skill. Even if you don’t know someone like this, there’s a very good chance that among the people you know, some know the types of people you’re looking for, but you don’t know who to ask for an introduction! Instead, it can be helpful to ask your social media contacts an open question: “Who is the best roboticist you know?” If several of your friends suggest the same person, that is a good indication that they are genuinely good at what they do.
• Tip of the tongue. Sometimes, it can seem like the most pressing problem in life is remembering something that’s on the “tip of your tongue.” It can be agonizing! Maybe you’re trying to recall the name of a show you used to watch on TV when you were younger, or identify a familiar-looking face in a historical photo. You may not know a single person who’s likely to know, but asking a large and diverse crowd, like the people on the Tip of My Tongue⁵ subreddit, often brings up the correct answer very quickly.
• Forecasting the future. It is not always clear who has information that will help predict a future outcome. For example, a candidate in an election might have a major scandal that is about to emerge, but only a few people know about it. Prediction markets are a way to bring out this wisdom from the crowd in a way that people can use.

Here’s how they work. The people who run the market set up a prediction, for example: “Jane Smith will win the 2020 election for mayor of Jonesville.” The organizers then set up a way for people to buy “shares” in different possible outcomes. If Smith wins the election, every share for her winning gets a dollar, and every share for her losing gets no money. Knowing this, people can buy and sell shares based on how likely they think she is to win. If you think there’s a 50% chance that she will win, you should be willing to pay $0.50 for a share that would pay $1.00 if you’re right. People who are very confident will have incentive to bet more money on the outcome, which affects the trading price.

If someone knows a scandal is about to ruin the chances of Smith’s election opponent, that means the odds of her winning will be higher. As a result, they will be willing to spend more money on shares for her winning—maybe $0.70 or $0.80 each. This will drive up the overall price of those shares. When you see the price rising like that, that can be a signal that people are betting based on information you don’t yet know. With many people participating in such a market, the best information tends to be revealed. This makes prediction markets often significantly more accurate than individual experts, or polls.

Whenever you try to harness the wisdom of crowds, it’s important to remember that crowds don’t always show their wisdom. Sometimes crowds act irrationally, usually because they all start thinking alike. According to James Surowiecki, wise crowds show the following four features:

• Diversity of information. Each person should have their own knowledge, experiences, or skills to contribute.
• Independence. Each person can form their initial opinions on their own, without having them determined by other people in the group.
• Decentralization. People should all be free to make their own decisions based on their own particular knowledge.
• Aggregation. There needs to be a mechanism like buying shares in a prediction market, voting or careful debate that allows the best ideas to rise to the top.

For more information, please see the following entries in the companion book A Chronicle of Ideas: A Guide for Superheroines (and Superheroes): Wisdom of Crowds.