The premise is that student translators should be provided with sufficient room, or a 'cognitive playground' in which they can explore solutions to translation problems. This study first gives a review of a widely used method of evaluating the translation process, the Think-Aloud Protocol (TAP) and states the limitations of TAP, followed by an introduction of translation commentaries by student translators as an alternative. The effect of writing translation commentaries accompanying translation assignments as a way to guide students to explore various issues related to translation tasks was examined through a comparison of commentaries by two student translators. Results showed that translation commentaries hold properties of TAP and successfully reflected the translation proficiency.