Flickering presentations do affect the judgment of learning but not the learning outcome

We examined whether visual disfluency, as elicited by presenting text on flickering slides, affects learning positively and the global judgment of learning (JOL) negatively. Participants (N = 202 in Experiment 1, between-subjects design; N = 53 in Experiment 2, within-subjects design) saw in an online session multiple slides including textual information that they had to learn. The slides were presented either fluently or disfluently, that is, interrupted by rapid presentations of black slides, evoking a flickering effect. Thus, instead of manipulating the textual material (e.g., by using different fonts), as most studies on the disfluency effect so far did, we manipulated the characteristics of the presentation (i.e., flickering vs. nonflickering). In both experiments, JOL was lower in the flickering than in the nonflickering condition. However, flickering slides did not lead to a better memory performance. The results provide further evidence for the assumption that a beneficial disfluency effect is questionable.