A new study led by researchers from Rice University and Michigan State University suggests that the academic field in which a scientist earned their doctorate may not accurately represent the field they are associated with decades later. Published in the journal PLOS One, the research introduces a new concept called "disciplinarity" to track how scientists’ professional identities evolve over time. The researchers developed a five-part Disciplinarity Scale, which measures how closely five aspects of a scientist’s current career—such as their department, professional associations, publishing habits, peer perceptions, and personal identification—align with the field of their original doctorate. The study analyzed survey responses from 4,113 science faculty members at 83 U.S. research universities who are on a tenure track. The findings suggest that scientists tend to have broader disciplinary affiliations the longer they have been out of graduate school. This trend was particularly noticeable among those who had experience with cross-disciplinary research. Around 16.6% of the participants reported that their current discipline was different from the one they studied for their doctorate, while about 83% remained in the same field they originally trained in. The new measure also highlighted differences in how closely scientists’ current work was tied to their original discipline, even among those who had not officially switched fields. For example, some scientists may still be working in their original field, but their professional activities may have expanded into related areas. The researchers suggest that future surveys could use both traditional disciplinary categories and the new Disciplinarity Scale to better understand how scientists' fields evolve over time. This approach could be especially valuable as universities and funding organizations increasingly support interdisciplinary research. By capturing both where scientists started and how their affiliations have changed, the new measure may help institutions better understand the shifting landscape of scientific careers and the growing importance of cross-disciplinary collaboration.