Confidence in Judgment: Persistence of the Illusion of Validity


This study examines the “illusion of validity”—the confidence humans have that we make accurate judgments even though the data proves we don’t.

The authors argue that two main factors contribute to the persistence of this illusion. First, positive outcomes are statistically quite likely even though our judgmental ability is low. Second, it’s hard to access negative results in non-laboratory settings—for example, you never know how many candidates you rejected would have gone on to be star performers. 

Together, these two factors make it easy for us to continue to believe we have great judgment when in fact we don’t. 

Key Points:

  • Multiple studies have shown that neither training, length of experience, nor the amount of information available to clinicians increased their predictive accuracy.
  • We attribute positive outcomes to our judgment that are actually the result of probabilities.
  • Difficulty accessing “disconfirming information”—information that proves we were wrong—helps maintain the illusion that we have great judgment.


Human judgment—even expert judgment—has been proven to be deeply inaccurate. 

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