The contributions of anchoring and past-test performance to the underconfidence-with-practice effect.

In the underconfidence-with-practice effect, people's judgments of learning (JOLs) typically underestimate memory performance across multiple study-test phases. Whereas the past-test hypothesis suggests that this underconfidence stems from participants' reliance on earlier test performance to make subsequent JOLs (despite new learning), the anchoring hypothesis suggests that the underconfidence stems from participants' reliance on a fixed psychological anchor point low on the JOL scale to make their JOLs. To contrast the predictions of these hypotheses, we had college students study, make JOLs, and test over several dozen paired-associate items across two study-test phases. We parametrically manipulated the presence or absence of testing and judging within participants during Phase 1. Contrary to the past-test hypothesis, items tested during Phase 1 demonstrated less underconfidence during Phase 2 than did nontested items. Furthermore, participants did not increase JOLs from Phase 1 to Phase 2 for items that they had not recalled or for items that had not been tested at all, suggesting that the underconfidence stemmed largely from participants' overreliance on a psychological anchor point to make their JOLs. Past test performance, however, seems to be a major cue that participants use to adjust their JOLs away from the anchor, reducing underconfidence. This was most evident when we used a between-participants manipulation (Exp. 2) to cause our participants to anchor their JOLs either high or low on the JOL scale, producing differential underconfidence independent of any adjustment. Taken together, these results support the anchoring hypothesis over the past-test hypothesis for explaining underconfidence with practice.