Researchers who work on course-based undergraduate research experiences (CUREs) and issues related to science, technology, engineering, and math (STEM) retention have begun exploring changes in student thinking about what it means to be a scientist. To support this effort, we developed rubrics to score answers to three open-response prompts: What does it mean to think like a scientist? What does it mean to do science? and Did you do real research in your coursename labs? The rubric development process was iterative and was based on input from the literature, experienced researchers, and early-career undergraduates. A post hoc analysis showed that the rubric elements map to 27 of 31 statements in the Culture of Scientific Research (CSR) framework, suggesting that scored responses to the three prompts can assess how well students understand what being a science professional entails. Scores on responses from over 400 students who were starting an introductory biology course for majors furnish baseline data from the rubrics and suggest that (i) undergraduates at this level have, as expected, a novice-level understanding of CSR, and (ii) level of understanding in novice students does not vary as a function of demography or academic preparation. Researchers and instructors are encouraged to add CSR to their list of learning objectives for CUREs and consider assessing it using the rubrics provided here.