Can people differentiate what they know from what they do not? Several lines of research suggest that people are not always accurate judges of their knowledge and often overestimate how much they know. Research on overconfidence finds that people commonly judge the accuracy of their judgments too favorably and typically overestimate how well they perform everyday tasks relative to other people. Work on the illusion of explanatory depth demonstrates that participants tend to think they have a better understanding of how objects work (e.g., a ballpoint pen) than they can demonstrate when that understanding is put to the test.
At times, people even claim knowledge they cannot possibly have, because the object of their knowledge does not exist, a phenomenon known as overclaiming. For example, in the late 1970s, nearly a third of American respondents expressed an opinion about the “1975 Public Affairs Act” when asked about it directly, even though the act was a complete fiction. Approximately a fifth of consumers report having used products that are actually nonexistent. More recent research has asked participants to rate their familiarity with a mix of real and nonexistent concepts, names, and events in domains such as philosophy, life sciences, physical sciences, and literature. Participants reported being familiar with the real items but also, to a lesser degree, with the nonexistent ones. […]
What underlies assertions of such impossible knowledge? We found that people overclaim to the extent that they perceive their personal expertise favorably. […]
A sizable body of work on how people evaluate their own knowledge suggests that they rely not only on a direct examination of their mental contents but also on a feeling of knowing. Notably, a feeling of knowing is often only weakly predictive of actual knowledge and appears to be informed, at least in part, by top-down inferences about what should be or probably is known. We theorized that such inferences are drawn from people’s preconceived notions about their expertise, inducing a feeling of knowing that then prompts overclaiming.