The original model by Dunning and Kruger holds that a lack of metacognitive abilities is responsible. Many models have been suggested that try to explain what underlying mechanisms cause the Dunning-Kruger effect. Since then various other studies have been conducted across a wide range of tasks, including skills from fields such as business, politics, medicine, driving, aviation, spatial memory, examinations in school, and literacy. It focused on logical reasoning, grammar, and social skills. The initial study was published by David Dunning and Justin Kruger in 1999. The Dunning–Kruger effect appears in both cases, but is more pronounced in relative terms the bottom quartile of performers tend to see themselves as being part of the top two quartiles. This can happen in either relative or absolute terms, i.e., in comparison with one's peer group as the percentage of peers outperformed or in comparison with objective standards as the number of questions answered correctly. This subjective assessment is then compared with how well they actually performed. For example, the participants in a study may be asked to complete a quiz and then estimate how well they performed. The Dunning–Kruger effect is usually measured by comparing self-assessment with a measure of objective performance. In popular culture, the Dunning–Kruger effect is often misunderstood as a claim about general overconfidence of people with low intelligence instead of specific overconfidence of people unskilled at a particular task. Some researchers also include in their definition the opposite effect for high performers: their tendency to underestimate their skills. The Dunning–Kruger effect is a cognitive bias whereby people with low ability, expertise, or experience regarding a certain type of task or area of knowledge tend to overestimate their ability or knowledge.

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