Answering a factual question today increases one's confidence in the same answer tomorrow - independent of fluency.

We investigated the cognitive processes that cause confidence to increase. Participants were asked 48 general-knowledge questions either once or three times, without feedback. After 2 min (Experiment 1) or 48 h (Experiment 2) they were asked the same questions again, and rated their confidence. Repeated questioning increased confidence but not accuracy. This increase, which replicated research on episodic memory in the eyewitness literature (e.g., Shaw, Journal of Experimental Psychology: Applied 2: 126-146, 1996), occurred even though accuracy was only around 25%. A mediation analysis identified response repetition, but not fluency, as a mechanism underlying growth in confidence. Thus, the basis for confidence judgments appears to be whether one's current response has been generated previously. In sum, answering a factual question increases confidence, but not accuracy, and this happens because learners use response repetition as a cue for confidence judgments.