Overconfidence is the tendency to be more confident in one’s judgments and abilities than is warranted by accuracy. People often know less, or perform less well, than they believe.

The bias appears in estimates of knowledge, predictions of future events, and assessments of personal skill. Students overestimate how well they will do on exams; professionals overestimate the accuracy of their forecasts. Calibration studies ask people to state their confidence and then compare that confidence with actual correctness; the gap is frequently large. Overconfidence is fueled by the availability of reasons that support one’s view, by the failure to consider alternative possibilities, and by the simple desire to see oneself as competent.

Moderate confidence can be useful; extreme overconfidence leads to poor planning, excessive risk-taking, and resistance to corrective feedback. Techniques that reduce the bias include considering the opposite, seeking disconfirming evidence, and tracking the accuracy of past predictions.

Feeling sure is not the same as being right. Overconfidence is the systematic gap between the two.