"Hard tasks tend to produce overconfidence but worse-than-average perceptions," reported Katherine A. Burson, Richard P. Larrick, and Jack B. Soll in a 2005 study, "whereas easy tasks tend to produce underconfidence and better-than-average effects.
"[1] The hard-easy effect falls under the umbrella of "social comparison theory", which was originally formulated by Leon Festinger in 1954.
[2] In a study reported in 1997, William M. Goldstein and Robin M. Hogarth gave an experimental group a questionnaire containing general-knowledge questions such as "Who was born first, Aristotle or Buddha?"
[6] Among the explanations advanced for the hard-easy effect are "systematic cognitive mechanisms, experimenter bias, random error, and statistical artifact".
[7] Psychological explanations for this phenomenon have also been offered up by Baranski and Petrusic (1994), Griffin and Tversky (1992), and Suantak et al.
"[7] In 2000, Juslin, Anders Winman, and Henrik Olsson of Uppsala University claimed that the hard-easy effect had previously "been interpreted with insufficient attention to important methodological problems".