Recent evidence suggests that making judgments of learning (JOLs) can directly modify subsequent memory performance, which is referred to as JOL reactivity. The present dissertation examined the underlying mechanism of JOL reactivity by (a) testing the two major theoretical explanations for JOL reactivity: the changed-goal hypothesis and the cue-strengthening hypothesis, and (b) pinpointing the retrieval processes that are modified by JOLs with the implementation of the dual-retrieval model. Here, the changed-goal hypothesis assumes that JOLs highlight the difference in learning difficulties among to-be-remembered items and switch learners’ goals from mastering all items to focusing more on easier items at the expense of harder items, thus producing negative reactivity for the latter. The cue-strengthening hypothesis posits that the act of making JOLs strengthens the cues that inform JOLs, thus producing positive reactivity when later memory tests are sensitive to the strengthened cues. In Experiment 1, I compared the reactive effects of item-level JOLs on associative recall between three types of word pairs that differ in learning difficulty: strongly related, weakly related, and identical pairs. In Experiment 2, I tested whether prestudy JOLs produced similar reactive effects as immediate JOLs on associative recall for related pairs. In Experiment 3, I investigated whether JOL reactivity was moderated by inter-item relation (word pairs whose targets were either semantically related or unrelated), JOL type (item-level or list-level), and test format (associative or free recall). In Experiment 4, I inspected whether reactivity of item-level and list-level JOLs was moderated by list organization (blocked or randomized) in free recall for categorical word lists. The experiments offered converging support for the cue- strengthening hypothesis rather than for the changed-goal hypothesis. Moreover, although positive JOL reactivity was always accompanied by improvements in recollection for item-specific verbatim details, it was also sometimes supported by enhancements in non-recollective operations (reconstruction and familiarity). Particularly, the process-level mechanism of JOL reactivity varied with material type, JOL type, and test format, which is consistent with the cue-strengthening hypothesis. Last, a contextual framework was recommended for further investigations into JOL reactivity.