Behind the Byline: A Large-Scale Study of Scientific Author Contributions

Understanding how co-authors distribute credit is critical for accurately assessing scholarly collaboration. In this study, we uncover the implicit structures within scientific teamwork by systematically analyzing author contributions across a large corpus of research publications. We introduce a computational framework designed to convert free-text contribution statements into 14 standardized CRediT categories, identifying clear and consistent positional patterns in task assignments. By analyzing over 400,000 scientific articles from prominent sources such as PLOS One and Nature, we extracted and standardized more than 5.6 million author-task assignments corresponding to 1.58 million author mentions. Our analysis reveals substantial disparities in workload distribution. Notably, in small teams with three co-authors, the most engaged contributor performs over three times more tasks than the least engaged, a disparity that grows linearly with team size. This demonstrates a consistent pattern of central and peripheral roles within modern collaborative teams. Moreover, our analysis shows distinct positional biases in task allocation: technical responsibilities, such as software development and formal analysis, broadly fall to authors positioned earlier in the author list, whereas managerial tasks, including supervision and funding acquisition, increasingly concentrate among authors positioned toward the end. This gradient underscores a significant division of labor, where early-listed authors mainly undertake most hands-on activities. In contrast, senior authors mostly assume roles involving leadership and oversight. Our findings highlight the structured and hierarchical organization within scholarly collaborations, providing deeper insights into the specific roles and dynamics that govern academic teamwork