Garden variety instances of confirmation bias occur in areas as disparate as the stock market, personal relations and legal conflicts. A more extreme case is the prosecution of the Iraq War, which is a textbook example of, among other things, an almost delusional myopia and the staggering enormity of the consequences to which it can lead.
A variety of cognitive illusions studied by Amos Tversky, Nobel Prize winner Daniel Kahneman and other psychologists are also discussed in "Expert Political Judgment." The book repeatedly underscores the idea that experts are as vulnerable to these illusions as most other people.
Tetlock did uncover one trait that the better predictors seemed to possess more than the less-successful ones. To name it, he used historian Isaiah Berlin's famous distinction between the hedgehog and the fox. Hedgehogs are thinkers who know one big thing, are in thrall to one overarching idea. Foxes, on the other hand, know many little things -- tricks, factoids, techniques -- and are wary of grand pronouncements and monolithic forces. Although less confident and less given to self-puffery, foxes make better predictors.
Foxes also more readily change their predictions in the light of unexpected events. Hedgehogs don't, in part because they're more subject to hindsight bias -- failing to remember their own mistaken predictions or retrofitting them to the facts. Alas, however, it is the hedgehogs who steadfastly adhere to simple (and often simplistic) ideas who generally become better known. Complexity confuses; simplicity sells.
Predicting political and economic events is a bit like picking stocks. Investors try to sense what the majority of other investors think about a particular stock before buying or selling. The task is very difficult, in part because the other investors are all trying to do the same thing. This self-referential and self-correcting aspect of the market makes unrelenting bullishness or bearishness appealing perhaps, but, overall, unprofitable. Those investors sensitive to subtly shifting investor attitudes do better.
Pundits, too, try to sense the mood of other pundits, policymakers and the general public before pontificating. This task, too, is very difficult, in part because many of the predicted are also predictors trying to do the same thing. This self-referential and self-correcting aspect of punditry makes predictions generated by big-idea hedgehogs memorable perhaps, but overall less reliable. Foxes, who "see the world as a shifting mixture of self-fulfilling and self-negating prophecies" that tend to "kick in as people recognize that things have gone too far" do better.
Uniting the two types of forecasts are the often surprisingly accurate prediction "markets" run by the University of Iowa and other organizations. In them, analysts can put at least a little bit of their money where their big mouths are. Such markets require clearly stated predictions. They bring the discipline of the market to forecasts that are often so nebulous as to be unfalsifiable. (As of this writing, the Iowa market predicts the Democrats will likely take the House but not the Senate.)
As Tetlock and others show, insights from cognitive science and probability theory have a role to play in the dicey business of predicting politics. Still, the best bet is described by Eugene Ionesco. The playwright wrote, "You can only predict things after they've happened."
Professor of mathematics at Temple University, John Allen Paulos is the author of best-selling books, including "Innumeracy" and "A Mathematician Plays the Stock Market." His "Who's Counting?" column on ABCNEWS.com appears the first weekend of every month.