Separation of encoding fluency and item difficulty effects on judgements of learning

The fluency of information encoding has frequently been discussed as a major determinant of predicted memory performance indicated by judgements of learning (JOLs). Previous studies established encoding fluency effects on JOLs. However, it is largely unknown whether fluency takes effect above and beyond the effects of item difficulty. We therefore tested whether encoding fluency still affects JOLs when numerous additional cues indicating the difficulty of an item are available as well. In three experiments, participants made JOLs for another participant while observing his or her self-paced study phase. However, study times were swapped in one experimental condition, so that items with short study times (indicating high fluency) were presented for long durations, whereas items with long study times (indicating low fluency) were presented for short durations. Results showed that both item difficulty and encoding fluency affected JOLs. Thus, encoding fluency in itself is indeed an important cue for JOLs that does not become redundant when difficulty information is available in addition. This observation lends considerable support to the ease-of-processing hypothesis.