Abstract：The development of the critical thinking ability is now an educational philosophy imple‐ mented worldwide. Research has shown that critical thinking can be practiced and perfected through language learning and use. There is, however, a notable paucity of research on how critical thinking can be measured in language assessments. The aim of this study was to explore how the critical thinking ability can be measured in integrated speaking assessment tasks, so as to provide justifications for incorporating critical thinking into the construct of integrated speaking assessments. First, a framework of discourse analysis was set up based on a review of literature on critical thinking. Speech samples of 48 test takers on the integrated speaking tasks of TOEFL iBT were then collected and coded on two dimensions: “textualization” and “reproduction of input material units”. Through correlation and multiple regression analyses, and supported by rater interview data, the study revealed that the critical thinking ability, in particular the abilities to comprehend, analyze, generalize and make inferences on the input materials, exerted a significant effect on test takers’ speaking performances. The study underscores the important role of critical thinking in integrated speaking performances and sheds light on the rating scale development in speaking assessment as well as the instruction and assessment of English speaking. Key words: critical thinking; speaking construct; spoken discourse analysis; integrated speaking assessment
