Changing patterns of self-citation: cumulative inquiry or self-promotion?

Self-citations are a familiar, if sometimes controversial, element of academic knowledge construction and reputation-building, contributing to both the cumulative nature of academic research and helping writers to promote their scientific authority and enhance their careers. As scholarly publications become more specialized, more collaborative and more important for promotion and tenure, we might expect self-citation to play a more visible role in published research and this paper explores this possibility. Here we trace patterns of self-citation in papers from the same five journals in four disciplines at three time periods over the past 50 years, selected according to their impact ranking in 2015. We identify a large increase in self-citations although this is subject to disciplinary variation and tempered by a huge rise in citations overall, so that self-citation has fallen as a proportion of all citations. We attempt to account for these changes and give a rhetorical explanation for authorial practices.