Here's a fun article for you couch psychologists out there. It's a study on incompetence, and how/why people who are incompetent (at something) are generally oblivious to their incompetence, and grossly overestimate their skills or knowledge in specific fields.

If you're not interested in reading, here's a figure from the article. The researchers asked the subjects how good they were at logic (relative to the students in their class), and then gave them a quick logic test. The subjects were asked to assess their performance after taking their test. The figure shows percieved competence, percieved test score, and actual test score. All numbers are in terms of percentile.