In a range of studies, participants have been requested to answer general knowledge questions, each of which had two possible answers, and also to estimate their chances of answering each question correctly.
In a study reported in 1997, William M. Goldstein and Robin M. Hogarth gave an experimental group was given a questionnaire containing general-knowledge questions such as "Who was born first, Aristotle or Buddha?" or "Was the zipper invented before or after 1920?".