This work identifies changes in dominant topics IntroductionMany evaluations of library and information science (LIS) have been conducted, primarily using the methods of content analysis and cocitation analysis on journal articles (e.g., Järvelin & Vakkari, 1993;White & McCain, 1998). The majority of these focus on a single period in LIS (e.g., Järvelin & Vakkari, 1990;Kumpulainen, 1991). Subsequent analyses often use different source titles, techniques, or coding schemes, making comparison between the analyses difficult. Although these studies constitute one lens on the field, there are some major limitations to the current literature in the area. First, the focus on a single communicative genre (the journal article) provides a monocular view of the field. Research has shown that the writing and citing patterns of authors vary significantly by genre (Bazerman, 1988;Hyland, 2000). A different topic spectrum may be found by examining topics across multiple genres. Second, the focus has been on either a group of highly cited authors or a sample of journal articles. Previous analyses have been manually intensive, necessitating small sample sizes. This has the potential to skew the results in two ways: (a) highly cited works are not necessarily representative of the works produced, and (b) a few articles/authors can heavily influence the results. Lastly, the analyses have been largely synchronic, rather than diachronic. Therefore, trend data rely on replication studies, which are not prevalent in the literature.Understanding the development of the discipline and changes in topics over time is particularly necessary in LIS, which has an extended literature of questioning its own disciplinary identity and the relationship of the library science and information science components of the name. Dissertations may serve a critical function in the exploration of disciplinary identity. During the doctoral process, students are acculturated in the ways of the discipline and are taught the central theories, methods, and objects of scrutiny within the domain. The dissertation is seen as independent and original research that is meant to set the foundation for the rest of the scholar's career. Therefore, it should accomplish two goals: situate the research within the domain, and explore new and original territory. Furthermore, although the primary focus of doctoral education is on the production of researchers (Sugimoto, 2010a), a secondary focus is the creation of new faculty. Therefore, the topics explored in doctoral dissertations may have an indirect effect on the education of the next generation of master's students.This study provides a new lens on disciplinary identity, by identifying the main topics in LIS dissertations from . A topic modeling technique, latent Dirichlet allocation (LDA) modeling, is used. We have both an historical and methodological objective: (a) to identify the main topics in LIS diachronically, and (b) to examine the use of LDA in analyzing disciplinary development and change.This work addresses gaps...

Interdisciplinarity has been studied using cognitive connections among individuals in corresponding domains, but rarely from the perspective of academic genealogy. This article utilizes academic genealogy network data from 3,038 PhD dissertations in Library and Information Science (LIS) over a span of 80 years (1930-2009) to describe interdisciplinary changes in the discipline. Aspects of academic pedigree of advisors and committee members are analyzed, such as country, school, and discipline of highest degree, to reveal the interdisciplinary features of LIS. The results demonstrate a strong history of mentors from fields such as education and psychology, a decreasing trend of mentors with LIS degrees, and an increasing trend in mentors receiving degrees in computer science, business, and communication, among other disciplines. This work proposes and explores the use of academic genealogy as an indicator of interdisciplinarity and calls for additional research on the role of doctoral committee composition in a student's subsequent academic career.

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