Does retrieval fluency contribute to the underconfidence-with-practice effect?

Judgments of learning (JOLs) made during multiple study-test trials underestimate increases in recall performance across those trials, an effect that has been dubbed the underconfidence-with-practice (UWP) effect. In 3 experiments, the authors examined the contribution of retrieval fluency to the UWP effect for immediate and delayed JOLs. The UWP effect was demonstrated with reliable underconfidence on Trial 2 occurring for both kinds of JOL. However, in contrast to a retrieval-fluency hypothesis, fine-grained analyses indicated that the reliance of JOLs on retrieval fluency contributed minimally to the UWP effect. Our discussion focuses on the status of the retrieval-fluency hypothesis for the UWP effect.