“They found that in many situations, those who can’t . . . don’t know they can’t. According to what’s now known as the Dunning-Kruger effect, it’s when we lack competence that we’re most likely to be brimming with overconfidence. In the original Dunning-Kruger studies, people who scored the lowest on tests of logical reasoning, grammar, and sense of humor had the most inflated opinions of their skills.”