The tendency for people with limited knowledge or competence to overestimate their abilities.
Dunning and Kruger’s research demonstrated that people who are unskilled in a certain arena tend to be unaware of their own incompetence. Because people with limited knowledge on a subject are unaware of their deficiencies, they generally assume that they are not deficient. Gerry just finished his Intro to Avalanches course. If he is suffering from the Dunning-Kruger effect, he might think that he is now an expert on the subject of avalanche safety and consequently make decisions that should require a more thorough understanding than he currently has.