The field of ESP has long been situated at a number of crossroads, where interdisciplinary practices, theories and methods overlap: Firthian linguistics, Discourse Analysis, System Functional Linguistics, Rhetorical Genre Theory, Second Language Acquisition, Writing Research, Social Constructivism, Sociocognitive Theories of Learning and Identity, and Linguistic Anthropology are but a few of the frames which have structured ESP over the past forty years. Such a wide range of theoretical and methodological contributions has proven necessary for explaining and describing the complexity of specialized linguistic phenomena. Within this broad context, the current study examines one specific type of linguistic phenomenon: the ‘order of indexicality’ (Blommaert 2010) which organizes textual practices in the field of Information Design. The function of indexicality is to elicit the activation of specific semiotic associations by means of specific textual forms. Knowledgeable insiders glean relevant meaning from these forms when the associated semiotic resources are activated, but without what is being ‘communicated’ necessarily appearing explicitly. As discussed in Dressen-Hammouda (2008, 2014), indexicality is an important object of research in ESP: given its implicit nature, it poses particular challenges to both teachers and learners in ESP. The current study describes the indexical order of the field of Information Design, using in-depth interviews with four professional information designers. The results are interpreted within the context of a wider longitudinal study, examining how students acquire relevant indexicality during the course of a bilingual, Information Design master's program. The results highlight the observation that teaching and learning indexicality does not consist of "a set of neatly isolated and easily teachable skills [but rather] a dynamic and mutually constitutive constellation of forces and processes that enable (and sometimes disable) the development of expertise" (Schriver 2012: 284). Even so, many ESP studies today continue to focus on ‘surface-level’ analyses of specialized discourses. This paper concludes with arguments why analyzing only what is discoursally explicit might be limiting. Bibliography: Blommaert, Jan. 2010. The sociolinguistics of globalization. Cambridge: Cambridge University Press. Bourdieu, Pierre. 1984. Distinction: A social critique of the judgment of taste. Harvard: Harvard University Press. Bucholtz, M., & Hall, K. 2005. Identity and interaction: A sociocultural linguistic approach. Discourse Studies, 7, 585-614. Dressen-Hammouda, D. 2008. From novice to disciplinary expert: Disciplinary becoming and genre mastery. English for Specific Purposes, 27, 233-252. Dressen-Hammouda, D. 2014. Measuring the voice of disciplinarity in scientific writing: A longitudinal exploration of experienced writers in geology. English for Specific Purposes 34, 14-25. Freedman, A., Medway, P. (Eds.). 1994. Genre in the new rhetoric. Bristol, PA: Taylor & Francis. Halliday, M. 1985. An introduction to functional grammar. London: Edward Arnold. Ivanič, R. 1998. Writing and identity: The discoursal construction of identity in academic writing. Amsterdam: John Benjamins. Lave, J. & Wenger, E. 1991. Situated learning: Legitimate peripheral participation. New York: Cambridge University Press. Lillis, T. 2008. Ethnography as method, methodology, and "deep theorizing": Closing the gap between text and context in academic writing research. Written Communication, 25, 353-388. Schriver, K. 2012. What we know about expertise in professional communication. In V. Berninger (Ed.), Past, present and future contributions of cognitive writing research to cognitive psychology. London, UK: Psychology Press/Taylor Francis Group, 275-312. Swales, J.M. 2004. Research genres: explorations and applications. Cambridge: Cambridge University Press. Tardy, C. 2009. Building genre knowledge. West Lafayette, IN: Parlor Press.