Because our impressions of how well each soldier performed were generally coherent and clear, our formal predictions were just as definite. We rarely experienced doubt or conflicting impressions. We were quite willing to declare: “This one will never make it,” “That fellow is rather mediocre, but should do O.K.” or “He will be a star.” We felt no need to question our forecasts, moderate them or equivocate. If challenged, however, we were fully prepared to admit, “But of course anything could happen.”
We were willing to make that admission because, as it turned out, despite our certainty about the potential of individual candidates, our forecasts were largely useless. The evidence was overwhelming. Every few months we had a feedback session in which we could compare our evaluations of future cadets with the judgments of their commanders at the officer-training school. The story was always the same: our ability to predict performance at the school was negligible. Our forecasts were better than blind guesses, but not by much.
Excellent piece by Daniel Kahneman in Sundays NYT magazine