Overconfidence is nearly universal. Not according to a widely publicized paper in last December's issue of the Journal of Personality and Social Psychology. Those who scored in the twelfth percentile in the logic test, for example, imagined that their skill in logic was at the sixty-eighth percentile. Now, if you are among the competent, you might derive some consolation from this research, since it implies that you are unlikely to be grossly overconfident. And there is more to worry about.
Overconfidence also tends to rise with the complexity of the problem.
Let me illustrate the point with an anecdote. Paul Erdos was one of the supreme mathematicians of the last century. He was also one of the world's leading experts on probability theory. Let's Make a Deal. You get to choose one of the doors and keep whatever is behind it.