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 titled "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."

It's so easy to judge other people, isn't it? In truth, though, the Dunning-Kruger effect leaves no brain unscathed: You do it, and you don't know you do it. As knowledgeable as you think you are in many areas, there are always areas you don't know about but think you do. If that leaves you feeling uneasy, Dunning has some words of comfort: "Over the years, I've become convinced of one key, overarching fact about the ignorant mind. One should not think of it as uninformed. Rather, one should think of it as misinformed." That is, an ignorant mind isn't empty; rather, it's full of the wrong information. Still, it's the only information you have, so you rely on it as if it's, well, reliable.

To overcome this, Dunning recommends being your own devil's advocate. Ask yourself how you might be mistaken, or how your expectations might turn out to be wrong. Don't assume you know — be a critic of the information you've got.

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To learn more about all of our hidden shortcomings, check out "You Are Not So Smart: Why You Have Too Many Friends on Facebook, Why Your Memory Is Mostly Fiction, and 46 Other Ways You're Deluding Yourself" by David McRaney. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.