As it turns out…the more specific reason that unskilled or incompetent people overestimate their abilities far more than others is because they lack a key skill called “metacognition.” This is the ability to know when you’re not good at something by stepping back, looking at what you’re doing, and then realizing that you’re doing it wrong. Good singers know when they’ve hit a sour note; good directors know when a scene in a play isn’t working; good marketers know when an ad campaign is going to be a flop. Their less competent counterparts, by comparison, have no such ability. They think they’re doing a great job.
Pair such people with experts, and, predictably enough, misery results. The lack of metacognition sets up a vicious loop, in which people who don’t know much about a subject do not know when they’re in over their head talking with an expert on that subject. An argument ensues, but people who have no idea how to make a logical argument cannot realize when they’re failing to make a logical argument. In short order, the expert is frustrated and the layperson is insulted. Everyone walks way angry.
Tom Nichols, The Death of Expertise, 45.