Sun, YutingHigher-order thinking is foundational to deeper learning and has been a major theme in the philosophical, psychological, and educational literatures. Multiple source use tasks (MSU) offer a rich context to investigate higher-order thinking, although systematic research on higher-order thinking in MSU contexts remains scarce. In addition, prior studies were often conducted in orchestrated settings, limiting their ecological validity. Guided by the Integrated Framework of Multiple Texts (List & Alexander, 2019), the current study aimed to unearth higher-order processes that unfolded over the Preparation, Execution, and Production stages of an ecologically valid MSU task. The study explored how a notetaking scaffold impacted higher-order processes, as manifested in the notes taken during the Execution stage and the argumentative essays written during the Production Stage.Participants were 105 undergraduate students enrolled in a course where MSU tasks are integral components. Over four class sessions, students completed learner characteristics measures, searched for sources online while completing a search log (Preparation stage), read and took notes on documents they selected (Execution stage), and wrote argumentative essays based on their notes (Production stage). Further, using a quasi-experimental design, students in the experimental class received a notetaking scaffold that prompted them to attend to key features of individual documents and integrate information across documents. The comparison class took notes in their preferred ways. Analyses revealed a variety of higher-order processes at each task stage. Students seemed to face more challenges in some processes (e.g., critical analysis, synthesis) than others (e.g., documenting evidence, justifying claims). The notetaking scaffold effectively facilitated some processes in notetaking (documenting source information) and essay writing (sourcing, counterarguing). Further, associations were found among processes occurring at different stages, with those related to sourcing and source evaluation being central. The study contributed to a more comprehensive understanding of students’ higher-order thinking across stages of a natural, class-based MSU task. Implications for future investigations using improved MSU tools and alternative analytical approaches and designs are discussed. Practically, the study pointed to the need for more explicit instructions and support in such areas as enhancing students’ understanding about argumentation and critical analysis of documents.enDissertationEducational psychologyHigher-order thinkingMultiple text comprehensionNotetaking scaffoldOnline searchingUndergraduate students