In early written corrective feedback studies, there were a lot of attempts to test if the feedback types are effective. This study was based on the assumption prevailing in the new era of studies of written corrective feedback, that feedback is effective. Firstly, it aims to compare the think-aloud protocols of the preferred and unpreferred feedback types which were chosen by 20 English learners (10 in preferred, and 10 in unpreferred feedback). To this aim, learners were asked to write diaries for six weeks. In each session, concurrent think-aloud protocols were employed and learners' verbal reports were extracted, and their mental processes were coded through developing a table of mental operations. In the second part of the study, the relative effectiveness of the preferred and unpreferred feedback was measured. Using the Chi-square goodness-of-fit test, the findings of the first part showed a significant difference between the mental operations for each feedback type. The results for the second part suggested that there is a significant difference between the effectiveness of the preferred and unpreferred feedback types. This latter finding indicates that the preferred feedback can facilitate the development of the accuracy in L2 learners' writing more than the unpreferred feedback.
