unconscious incompetence

In 1999 a pair of researchers published a paper called "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments (PDF)." David Dunning and Justin Kruger (both at Cornell University's Department of Psychology at the time) conducted a series of four studies showing that, in certain cases, people who are very bad at something think they are actually pretty good. They showed that to assess your own expertise at something, you need to have a certain amount of expertise already.