With its distinct characteristics, the research article (hereafter RA) abstract has been a major area of interest within the field of metadiscourse. Investigating authorial presence displayed in RA abstracts can play an important role in illuminating the nature of the interaction among the writer, the text, and the reader. This study aimed to shed light on the disciplinary variation on how much, and for what purposes, authorial presence is shown in RA abstracts through the use of the first-person plural pronoun "we" as an engagement marker (the inclusive form) and a self-mention device (the exclusive form) using a corpus of RA abstracts in the fields of Bioengineering and Software Engineering (hard sciences), and Psychology and Sociology (soft sciences). The inclusive "we" was found to be very rare, therefore, the majority of the analysis focused on the exclusive "we." The results indicated a considerable variation across the sampled disciplines and a general tendency to use self-mention when explaining purposes, procedures, and results, but not when introducing and concluding, or elaborating arguments. The findings of this study will contribute to a deeper understanding of the disciplinary variation in the use and communicative functions of "we," which could enhance academic writing practices.