About Dunning-Kruger effect, the cognitive bias where incompetent people grossly overestimate their skill level.
But something curious started happening as we began to look at the people who did extremely badly on our little quiz. By now, you may be able to predict it: These people expressed more, not less, confidence in their performance. In fact, people who got none of the items right often expressed confidence that matched that of the top performers. Indeed, this study produced the most dramatic example of the Dunning-Kruger effect we had ever seen: When looking only at the confidence of people getting 100 percent versus zero percent right, it was often impossible to tell who was in which group.
