The wisdom of many in one mind

Researchers have demonstrated that the power of averaging somewhat contradictory, yet plausible, predictions can be used to exploit the quantitative judgments made by a single person. By using a technique they call “dialectical bootstrapping”, the “wisdom of crowds” can be created within a single mind.

As a forecaster, you will recognize the following two situations:
-The experts you consulted made contradictory predictions.
-Depending on which statistical models, modeling assumptions, or data sets you use, your forecasts differ.

What should you do with these contradictory, yet plausible forecasts? A time-proven solution is to mechanically average the differing predictions. As long as the errors of the predictions are at least somewhat independent, the average will be consistently more accurate than an individual prediction (and sometimes the average will be better than the best prediction). But what if you cannot construct a statistical model and can only ask a single expert? Using a technique called "dialectical bootstrapping" Herzog and Hertwig (2009) have demonstrated that the power of averaging somewhat contradictory predictions can be applied to quantitative judgments made by a single person. Try it for yourself: What will be the US inflation rate for the last quarter of 2009? First, make your best guess and write it down. Second, temporarily assume that your first prediction is off the mark. Think about a few reasons why that could be. Based on this new perspective, make a second, rival ("dialectical") estimate and write it down. Finally, use the average of both estimates as your prediction.

In a study on quantitative estimates (e.g., "In what year was electricity discovered?"), the authors showed that this simple technique improves accuracy because it elicits two somewhat independent estimates. They observed similar results in a study in which people twice predicted the representation of the Swiss political parties that would result from the 2007 election, when participants were asked to make predictions both from their own perspective and from that of a dissimilar other person. Vacillating between forecasts can be agonizing. But, as dialectical bootstrapping illustrates, being of two minds can also work to one's advantage.

Herzog, S. M., & Hertwig, R. (2009). The wisdom of many in one mind: Improving individual judgments with dialectical bootstrapping. Psychological Science, 20, 231-237. Working paper available

Source: Forecasting Principles