Two experiments investigated the role of metacognition in changing answers to multiple-choice, general-knowledge questions. Both experiments revealed qualitatively different errors produced by speeded responding versus confusability amongst the alternatives; revision completely corrected the former, but had no effect on the latter. Experiment 2 also demonstrated that a pretest, designed to make participants' actual experience with answer changing either positive or negative, affected the tendency to correct errors. However, this effect was not apparent in the proportion of correct responses; it was only discovered when the metacognitive component to answer changing was isolated with a Type 2 signal-detection measure of discrimination. Overall, the results suggest that future research on answer changing should more closely consider the metacognitive factors underlying answer changing, using Type 2 signal-detection theory to isolate these aspects of performance.