Overprecision in judgment is the most robust type of overconfidence, and the one least susceptible to debiasing. It refers to people's excessive certainty in the accuracy of their estimates, predictions or beliefs. Research on overprecision finds that confidence intervals, estimated ranges that judges are confident will include the correct answer, tend to include the correct answer significantly less often than what their assigned confidence level would suggest. For example, 90% confidence

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... vals typically include the correct answer about 50% of the time (Klayman, Soll, González-Vallejo, & Barlas, 1999). By this standard, confidence intervals appear too narrow, or overprecise. This dissertation focuses on effectively reducing this bias. In this dissertation, I present a novel elicitation method which can reduce overprecision, sometimes eliminating the bias. This method, called Subjective Probability Interval Estimates, or, in short, SPIES, presents the judge with the entire range of possible values, divided into intervals. The judge estimates, for each interval, the probability that it includes the correct answer. Since these intervals include the entire range of possible values, the sum of these subjective probabilities is constrained to equal exactly 100%. This work presents six experiments, organized in two parts. Part I focuses on the use of SPIES for eliciting quantitative estimates, and tests it against other elicitation methods in three experiments. Experiment 1 included a within-subject comparison of SPIES and two other elicitation methods, namely 90% confidence intervals and 5th and 95th fractile estimates, and found that SPIES produce interval estimates with significantly higher hit-rates than the other two methods. Experiment 2 varied the range which the SPIES task spanned and the number of intervals included in it, and found that SPIES outperformed the confidence interval method across all configurations. Experiment 3 tested the robustness of this effect to different value 5 scales, and to vari [...]