A 2009 study concluded "that all types of judges exhibit the hard-easy effect in almost all realistic situations", and that the presence of the effect "cannot be used to distinguish between judges or to draw support for specific models of confidence elicitation" [REF].
A 1999 study suggested that the difference between the data in two studies, one performed in Canada by Baranski and Petrusic (1994) and the other in Sweden by Olsson and Winman (1996), "may reflect cross-national differences in confidence in sensory discrimination" [REF].