Reexamining the sources of variance in recognition confidence: A reply to Kantner and Dobbins (2019)

Recently, Kantner and Dobbins (Psychonomic Bulletin & Review, 26(4), 1317-1324, 2019) reported a reanalysis of a series of previously published data sets in which they examined the sources of variation in recognition memory confidence ratings. Although between-subject differences in mean levels of confidence tended to account for the majority of variance in confidence ratings for both "old" and "new" decisions, the contribution of overall subject-level variation to confidence ratings for "new" decisions was noticeably and consistently larger. Here, I report a series of quantitative simulations along with a reanalysis of the original data to demonstrate that the relatively greater subject-level variation in mean confidence seen for "new" as compared with "old" recognition decisions largely reflects statistical constraints imposed by (a) the range limits of the ordinal scale used to measure confidence, and (b) the stronger relation between memory accuracy and confidence in "old" decisions. Therefore, any observed difference in the extent of subject-level variation in mean confidence between "old" and "new" recognition decisions need not imply a meaningful psychological distinction. These findings point out what in my view is an important statistical constraint that should be considered by researchers interested in understanding the bases of variation in memory confidence.