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Author co-citation analysis (ACA) has been used to explore changes in the intellectual base of the information retrieval (IR) field over two consecutive time periods: 1987–1991 and 1992–1997. Thirty-nine highly cited IR researchers were selected as the research sample. Multidimensional scaling (MDS) and clustering techniques (CT) were used to create the two-dimensional maps to display the dynamic intellectual structure of IR, based on scholars citing their work over these two time periods. Factor analysis (FA) has been used to reveal the ‘breadth’ of the authors’ research areas. ACA offers a good technique that contributes to the understanding of intellectual structure in the sciences and possibly in other areas to the extent that those areas rely on formal scholarly communication such as serial publications. Nonetheless, obvious drawbacks exist in ACA. These include the subjective nature of the interpretation of results, the difficulty of readily identifying clusters and the inability to distinguish collaborative research relationships between authors. Thus, ACA by itself is insufficient. However, ACA can be enhanced significantly when combined with FA to give a more accurate and useful picture of the MDS results. Introduction As the structure of our society becomes increasingly complex, individuals and groups need to communicate an increasing volume of information. Schramm [1], a dominant figure in the communication sciences, once said that the field of communication was like ‘an oasis in the desert, where many trails cross, and many travellers pass, but only a few tarry’. Bibliometrics or ‘the application of mathematics and statistical methods to books and other media of communication’ provide a method for examining communication among scholars in a field through their scholarly publication [2]. The introduction of the bibliometric method into communication science has led to a rapid growth in both the number and types of studies [3, 4]. Bibliometrics encompasses a number of empirical methods, citation and co-citation analysis [5]. In particular, they can be applied to the formal record of scholarly communication from different points, such as authors, journals and textual content. Author co-citation analysis (ACA), a well-established technique in bibliometrics, is a potentially productive method of examination of the advantages of the cognitive/intellectual structure of science specialities. Numerous studies use ACA to map the intellectual base of specialities that have included, for example, organisational behaviour [6], communication science [7], information science [8], marriage and family research [9], scholarly communication in the sociology of science and information science [10] and others [11]. This paper describes the use of author co-citation mapping to study changes in the intellectual structure of information retrieval (IR) over the past consecutive eleven years. This is further divided for analysis into two time frames; namely, 1987–1991 and 1992–1997. 1 2 3 4 5 6 7 8 9 1110 1 2 3 4 5 6 7 8 9 20 1 2 3 4 5 6 7 8 9 30 1 2 3 4 5 6 7 8 9 40 1 2 3 4 5 6 7 8 9 50 1 2 Journal of Information Science, 25 (1) 1999, pp. 67-78 67 The effect of postings information on searching behaviour Mapping the intellectual structure of information retrieval studies: an author co-citation analysis, 1987–1997 Correspondence to: Y. Ding, Division of Information Studies, School of Applied Science, Nanyang Technological University, Nanyang Avenue, Singapore 639798. E-mail: [email protected] 3157 JIS 25/1 07 DING 22/12/98 4:11 pm Page 67 © 1999 Chartered Institute of Library and Information Professionals. All rights reserved. Not for commercial use or unauthorized distribution. at PENNSYLVANIA STATE UNIV on February 5, 2008 http://jis.sagepub.com Downloaded from