–Justin Kruger, assistant professor of psychology at the University of Illinois, and David Dunning, professor of psychology at Cornell University, on people who do things badly but think they do them well, New York Times, Jan. 18.
Across 4 studies, the authors found that participants scoring in the bottom quartile on tests of humor, grammar, and logic grossly overestimated their test performance and ability. Meanwhile, people with true knowledge tended to underestimate their competence.
APA Journal Well worth the read.
Or, you can take a look at the WIKIPEDIA article.