Dunning–Kruger effect

The Dunning–Kruger effect is a bias in thinking, usually where a person is unaware of how badly they grasp a subject, not understanding that they are failing at it. They mistakenly think that they are doing as well as "average" or even "above average".
It is a psychological effect in which people don't realize their level of knowledge or ability in a subject. People who know little about a subject will think that they know more than they actually know. People of low ability may not have enough intelligence to fully grasp how complicated something can be, causing them to overestimate their knowledge or ability. This can cause them to underestimate the intelligence of a high ability person who claims something is complicated when they falsely believe they understand it fully. 
This effect was shown in an experiment that was done by Justin Kruger and David Dunning at Cornell University.
The investigators said:
In 2000, Dunning and Kruger were awarded the Ig Nobel Prize in the field of psychology for their study.