Consider the original study: they used 45 Cornell undergraduate students and asked them about grammar. Grammar isn't objective. Everyone there had performed wel

Consider the original study: they used 45 Cornell undergraduate students and asked them about grammar. Grammar isn't objective. Everyone there had performed well on the verbal portion of the SAT, but they weren't studying grammar and hadn't gotten instruction on this particular book of grammar they were judged against. It is very likely that what they were capturing in the "better" or "worse" scores is differences in local dialect. They then judged people whose beliefs about grammar varied from the one book's beliefs about grammar as having over-estimated their performance. They took people out of one context, asked them how they would behave in a novel context, and everyone made an educated guess. The people who guessed correctly were judged to accurately know their own abilities, when actually they may just have gotten lucky. Thus what Dunning-Kruger's paper actually says is that if you want people to know how you would like them to perform a task, you can't assume they will read your mind: you have to provide them with actual feedback on their performance.