Psychologist David Dunning has long studied people's awareness of their own thinking processes—an area of science known as metacognition. In 1999, he and his then-graduate student Justin Kruger published a paper in the Journal of Personality and Social Psychology entitled "Unskilled and Unaware of It: How Difficulties In Recognizing One's Own Incompetence Lead to Inflated Self-Assessments." In it, the researchers performed a series of experiments that asked college students to rate how funny jokes were (which they compared with ratings from professional comedians), identify grammar errors, and answer questions dealing with logical reasoning. Across the board, those who did the worst on the tests thought they did the best. Interestingly, those who did the best tended to underestimate their ability. In the paper, the researchers laid out the sad truth: incompetent people can't know they're incompetent because their incompetence is the very thing that robs them of the ability to realize how incompetent they are.
But this goes further than people just not knowing about their own incompetence. "What's curious," Dunning wrote in Pacific Standard, "Is that, in many cases, incompetence does not leave people disoriented, perplexed, or cautious. Instead, the incompetent are often blessed with an inappropriate confidence, buoyed by something that feels to them like knowledge."