This repository contains the supporting research data and instruments for a study evaluating the user experience of real-time autocomplete features in AI-assisted academic writing. The uploaded materials include the NASA-TLX questionnaire document, the Retrospective Think Aloud (RTA) test instruction document, NASA-TLX respondent results, and RTA respondent results. The dataset supports a mixed-method evaluation of user experience and cognitive load in the context of Human-AI Co-Creation during academic writing. The quantitative component is based on NASA-TLX, while the qualitative component is based on Retrospective Think Aloud responses. The data and instruments are provided to support academic transparency, reproducibility, and citation of the research materials.