Across four studies, we found that participants scoring in the
bottom quartile on tests of humor, grammar, and logic grossly
overestimated their test performance and ability. Although their
test scores put them in the 12th percentile on average, they
estimated themselves to be in the 62nd percentile (Kruger & Dunning,
in press). As Charles Darwin sagaciously noted over a century ago,
"ignorance more frequently begets confidence than does knowledge."
-- Justin Kruger
(http://www.psych.uiuc.edu/people/faculty/kruger.html)
Kruger, J., & Dunning, D. "Unskilled and unaware of it:
How difficulties in recognizing one's own incompetence lead to
inflated self-assessments." Journal of Personality and Social
Psychology. December 1999.