Knowledge dissemination and evidentiality in the genre of posters. Anatomy of a condensed medical discourse

The genre of scientific posters is a very complex one, because it implies combining written and oral modes in communication. Such complexity is further increased by the fact that posters are created in such a way as to stand alone and do the talking, while showing medical research, all in a single visual plan. Such extreme conciseness is possible only if redundant information, seen as accessory matters, is deleted. As pointed out by Hobbs (2003, p. 459), this means that in the medical context the cohesion usually provided by explicit linkage is supplied by the reader’s background knowledge. In this context, the evidential markers, while facilitating the understanding of poster cognitive mapping, indicate the author’s level of expertise towards knowledge. Given the fact that consistent linguistic investigations of posters are almost absent from an applied linguistics perspective, it is the aim of this study to describe how evidentiality is realized in such a condensed and specialized genre. More specifically, drawing on Chafe (1986), this investigation will be focused on those linguistic forms regarded as evidential markers and showing various degrees of knowing within the written form of medical posters, in order to illustrate how evidentiality is linguistically realized, and what, if any, pragmatic functions it has. This investigation, based on the analysis of the verbal components of a corpus of 28 medical posters published online between 2002 and 2011, has been carried out on attested language use in the written discourse of medical posters. The findings highlight the fact that evidentiality is dependent on the socio-interactional work the speaker does to construct authority, responsibility and entitlement in a particular context and with particular recipients