I’ve noticed that some bright people confidently state that the Dunning-Kruger effect is caused by lack of intelligence rather than by a lack of knowledge. They probably believe that they will never fall victim to the DK effect themselves because it affects only those who are stupid, and they are not.

That belief is wrong, and anyone knows that who has witnessed a bright person confidently make statements that are completely inaccurate and wrong-headed regarding a subject of which they have little or no knowledge.

The problem is not lack of intelligence, but lack of knowledge — it’s not stupidity, but ignorance. Even very bright people are ignorant in many, many subjects, and practitioners who are knowledgeable in those subjects can offer up many examples of the DK effect in bright people. My wife is a UX designer, and she often regales me with incredibly bad suggestions for changes to a web interface confidently proposed by very bright people who have no knowledge of interaction design — so little knowledge, in fact, that they have no clue as to the depth of their ignorance. And not only will they offer bad suggestions, they often will try to insist that those suggestions be implemented: DK in action. Their ignorance makes them confident, and not being stupid doesn’t help them at all.

I suggest rewriting “The Dunning-Kruger effect posits that dumb people are too stupid to know they are dumb.” to be “The Dunning-Kruger effect is the inappropriate (and unfounded) confidence of a person in a subject area about which they know so little that they are unable to recognize the degree of their ignorance.”

Restated that way, it’s clear that even very intelligent people can fall victim to the DK effect once they stray too far from their field of expertise.