Calibration trumps confidence as a basis for witness credibility

ABSTRACT—Confident witnesses are deemed more credible than unconfident ones, and accurate witnesses are deemed more credible than inaccurate ones. But are those effects independent? Two experiments show that errors in testi-mony damage the overall credibility of witnesses who were confident about the erroneous testimony more than that of witnesses who were not confident about it. Furthermore, aftermaking an error, less confident witnesses may appear more credible than more confident ones. Our interpreta-tion of these results is that people make inferences about source calibration when evaluating testimony and other social communication. How do you decide whether another person is a reliable source of information? In everyday life, you may rely on the other person’s expressions of confidence, history of accurate (and erroneous) statements, and opportunity to be well informed on the subject of the assertion, as well as on your own inferences about the per-son’s motives and character and, in some cases, your beliefs about his or her expertise. Such habits are very general and apply to people’s evaluations of everyone, including their ac-quaintances, friends, and advisors. Judgments of credibility are especially important in trials. Many behavioral studies show that jurors, or mock jurors, rely on expressed confidence when evaluating eyewitnesses ’ credibilit