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See Inside October/November 2008

Are Three Guesses Better Than One?

Averaging your guesses is better than trying only once



© Peter Booth/iStockPhoto

The U.S. houses what percentage of the world’s airports? If you asked several people this question and averaged their guesses, you would probably end up closer to the right answer (30.5 percent) than if you asked just one person. This “wisdom of the crowd” effect has long been recognized, but scientists have recently gone a step further by showing that the strategy works even when the “crowd” consists of only one person.

Psychologists Edward Vul of the Massachusetts Institute of Tech­nol­ogy and Harold Pashler of the Uni­versity of California, San Diego, asked 428 participants various trivia ques­tions and then, without warning, asked them to guess again later. On average, a person’s combined responses were more accurate than either of his or her guesses alone, the authors reported in Psychological Science in July.

The findings support the notion that cognition may be described as statistical inference, meaning that people base their thoughts and judgments about the world on statistical probabilities, Vul says. When trying to answer a trivia question, people construct a range of possible values based on their knowledge. Each guess then represents one sample from that distribution, he says. For example, people might approach the question about the percentage of airports by imagining a world map showing the distribution of airports, Vul explains, “but because their knowledge is probabilistic the map they construct will be different for each guess.”

Note: This story was originally printed with the title, "Go Ahead, Change Your Mind".

This article was originally published with the title "Go Ahead, Change Your Mind."

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