Mind & EverydayFact
People who know little often can't tell.
Dunning and Kruger found in 1999 that participants in the bottom quarter on logic and grammar tests rated themselves around the 62nd percentile. Lacking skill means lacking exactly the knowledge needed to see your own gap. Caveat: part of the effect is pure statistics, since self-ratings tend to drift toward the middle.
Useful: If something looks trivially easy to you but hard to experts, you're probably missing something.
Source: en.wikipedia.org