The Dunning Kruger Effect (DKF) describes the phenomenon whereby incompetent individuals believe they are competent despite lacking expertise or skill. The DKF was first described by psychologist Daniel J. Siegel in his book Thinking, Fast and Slow. According to Siegel’s theory, it occurs because “people with low intelligence tend to overestimate their own ability and competence while underestimating those of others.” 
In his book, Siegel writes that the problem is exacerbated by a number of factors including:
Individual differences in cognitive abilities;
People’s tendency to view themselves as experts in areas where they have little experience or expertise; and,
A failure of self-awareness.
Siegel further notes that the problem may not occur to everyone, but rather only to some degree. Individuals with high levels of confidence in their own abilities will often fail to recognize that they lack expertise or skills in certain areas. For example, someone who believes she is a good cook might be unable to see how her poor cooking techniques could lead to food poisoning.
The DKF has been studied in everything from driving to medical care. In general, individuals with less experience or skill are more likely to the DKF, but it can also lead to more widespread failures in judgment and competence.
The problem is not limited to incompetence either. It can also cause a lack of recognition of one’s own abilities and accomplishments. For example, individuals who achieve great things are often the last to recognize their own greatness.
How to Avoid the DKF and Why You Should Know You Don’t Know Everything is a great article about the severe loss of ability to think rationally and have an accurate perception of reality due to a condition of total ignorance. This is a long but excellent article and explains why you should not think you are an expert in everything. I won’t even bother attempting to summarize it as it would not do justice to the quality and content of this masterpiece.
This is a true story (with some minor details changed) about how I learned very quickly not to make the same mistake that many think they know everything and they really do not. When I had completed my training as an Air Force Flight Surgeon, I was assigned to an Air Force flight training squadron and named the “Flight Surgeon in Charge”. This meant that I was responsible for the medical care of all the flying officers in this unit. My first day on the job was supposed to be spent shadowing the Flight Surgeon in Charge so that I could learn the ropes.
On the first day of shadowing, we started off with a visit to the local hospital. The doctors there had called the base and said they had an airman who had been severely burned, and needed to see a burn specialist as soon as possible. We went to see this airman, and found him standing outside the hospital, with his shirt off. It was readily apparent what the problem was. He was blackened from head to toe with 2nd degree burns.
The conversation went something like this:
Flight Surgeon: “How did this happen?”
Airman: (whispering) “I touched the tail pipe of a truck that had just started up.
Flight Surgeon: “Why would you do a thing like that?”
Airman: (even more of a whisper) “To see if it was hot.”
These questions went on for quite a while, with the burn patient obviously wanting to tell us more than he was telling us. Finally, he spilled the beans about why he was really at the back of this truck.
He said, “They told me to go find out if the truck was hot.”
We looked at each other, and I had to ask the next question.
Me: “Who is they?”
Airman: “The sergeants.”
We looked at each other again, and realized that whatever the reason for this incident, it was not due to some freak accident.
Sources & references used in this article:
For the law, neuroscience changes nothing and everything by S Zeki, OR Goodenough… – … Transactions of the …, 2004 – royalsocietypublishing.org
Knowing everything about nothing: specialization and change in research careers by JM Ziman, JM Ziman – 1987 – books.google.com
Everything you know about Indians is wrong by PC Smith – 2009 – books.google.com
Knowing “the price of everything and the value of nothing”: accounting for heritage assets by K Hooper, K Kearins, R Green – Accounting, Auditing & Accountability …, 2005 – emerald.com
What Maesters Knew: Narrating Knowing by B Cowlishaw – Mastering the Game of Thrones: Essays on …, 2015 – books.google.com