Seeking a Second Opinion

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Science  06 Mar 2009:
Vol. 323, Issue 5919, pp. 1267
DOI: 10.1126/science.323.5919.1267b

A marketplace—whether for ideas or goods and services—provides a remarkably efficient means of information exchange, and prediction markets yield astonishingly accurate forecasts of election outcomes, Oscar winners, and so forth. But how might a single individual, lacking access to the wisdom of the crowds, attempt to improve his or her best guess? Herzog and Hertwig offer one prescription based on the Hegelian dialectic: After making the first estimate, consider the reasons and assumptions underpinning that estimate (and how they might be off target), and then formulate a new, second estimate. They tested the efficacy of this method by asking university students to date a collection of 40 historical events covering the past four centuries and tabulating the average of repeated guesses from the same individual, which is analogous to standard reliability sampling, to the average (synthesis) of the dialectical guesses (thesis and antithesis). They found that the improvement in accuracy (in years) over the first estimate was twice as large for the dialectical average than for the repeat average, although averaging the first estimates from two random individuals worked better still. — GJC

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