Effect of overlearning on the feeling of knowing is more detectable in within-subject than in between-subject designs

Conflicting results in the literature concerning the influence of overlearning on subsequent feeling of knowing (FOK) judgments for unrecallable items were resolved in an experiment that contrasted within-subject and between-subject designs. In the between-subject design, participants gave FOK judgments about items all of which had been learned to a criterion of either one or six correct recalls 4 weeks earlier. In the within-subject design, these judgments were made about the same items, half of which had been correct once and half six times. Results showed that the effect of overlearning on FOK ratings was more detectable in the within-subject design than in the between-subject design. It is suggested that future experiments on metacognition should use within-subject designs for maximal detectability of the effect of an independent variable on metacognitive judgments.