PurposeThe introduction of “altmetrics” as new tools to analyze scientific impact within the reward system of science has challenged the hegemony of citations as the predominant source for... Show morePurposeThe introduction of “altmetrics” as new tools to analyze scientific impact within the reward system of science has challenged the hegemony of citations as the predominant source for measuring scientific impact. Mendeley readership has been identified as one of the most important altmetric sources, with several features that are similar to citations. The purpose of this paper is to perform an in-depth analysis of the differences and similarities between the distributions of Mendeley readership and citations across fields.Design/methodology/approachThe authors analyze two issues by using in each case a common analytical framework for both metrics: the shape of the distributions of readership and citations, and the field normalization problem generated by differences in citation and readership practices across fields. In the first issue the authors use the characteristic scores and scales method, and in the second the measurement framework introduced in Crespo et al. (2013).FindingsThere are three main results. First, the citations and Mendeley readership distributions exhibit a strikingly similar degree of skewness in all fields. Second, the results on “exchange rates (ERs)” for Mendeley readership empirically supports the possibility of comparing readership counts across fields, as well as the field normalization of readership distributions using ERs as normalization factors. Third, field normalization using field mean readerships as normalization factors leads to comparably good results.Originality/valueThese findings open up challenging new questions, particularly regarding the possibility of obtaining conflicting results from field normalized citation and Mendeley readership indicators; this suggests the need for better determining the role of the two metrics in capturing scientific recognition. Show less
The research presented in this PhD thesis describes ways of identifying at an early-stage, 2-3 years after their publication, discoveries in science that are expected to have a major impact on... Show moreThe research presented in this PhD thesis describes ways of identifying at an early-stage, 2-3 years after their publication, discoveries in science that are expected to have a major impact on science. Bibliographic information extracted from those scientific publications is analysed to select patterns that may identify such `scientific breakthroughs’. A distinction is made between different types of breakthroughs. A major methodological issue is the differentiation between discoveries that actually achieve a long-term major impact on science and those where the impact has not occurred within the first three years. These impacts are measured in terms of `citations’ from subsequent research publications.This thesis introduces the conceptual framework that is used to analyses four case studies, each study focussing on a specific well-documented breakthrough discovery. The citation impact patterns are analysed in a search for bibliographic markers that are characteristic for a breakthrough discovery. The significance of the various markers, one set of markers for each type of breakthrough, were tested in a large-scale validation study.This study resulted in several early-stage identification algorithms. Five of these algorithms were implemented as automated computerized search methods. The algorithms have proved able, retrospectively, to identify early-stage publications that present (potential) breakthrough discoveries. Show less
Bibliometric studies often rely on field-normalized citation impact indicators in order to make comparisons between scientific fields. We discuss the connection between field normalization and the... Show moreBibliometric studies often rely on field-normalized citation impact indicators in order to make comparisons between scientific fields. We discuss the connection between field normalization and the choice of a counting method for handling publications with multiple co-authors. Our focus is on the choice between full counting and fractional counting. Based on an extensive theoretical and empirical analysis, we argue that properly field-normalized results cannot be obtained when full counting is used. Fractional counting does provide results that are properly field normalized. We therefore recommend the use of fractional counting in bibliometric studies that require field normalization, especially in studies at the level of countries and research organizations. We also compare different variants of fractional counting. In general, it seems best to use either the author-level or the address-level variant of fractional counting. Show less
The research described in this thesis aims to establish the use of detailed collaboration and citation analysis combined with other forms of bibliometric analysis as a tool enabling a better... Show moreThe research described in this thesis aims to establish the use of detailed collaboration and citation analysis combined with other forms of bibliometric analysis as a tool enabling a better understanding of the organization of scientific communities and the way knowledge is spread inside scientific communities. In the study of collaboration networks the main goal is to identify existing research groups, potential research groups, and patterns of collaboration. The analysis of citations networks through specific measures and metrics, on the other hand, makes it possible to identify main lines of research through the years. Thus, such analyses improve our understanding of the growth and decline of fields, including phenomena such as paradigm shifts and emerging research themes. Network measures and metrics also allow for the identification of important nodes (e.g., journals, articles) embedded in the citation network. Show less
Interdisciplinarity of research is a hot topic because of new developments occurring at frontiers of disciplines (e.g. nanoscience), but also because of the urge for societal relevance of research.... Show moreInterdisciplinarity of research is a hot topic because of new developments occurring at frontiers of disciplines (e.g. nanoscience), but also because of the urge for societal relevance of research. A lot has been written on interdisciplinarity, however, relatively little empirical research has been carried out. In this thesis the value of quantitative, in particular bibliometric methods in research on interdisciplinarity is investigated and these methods are applied in a number of case studies. Methods are applied in three ways: in order to determine the interdisciplinary character of research; to validate evaluation processes in science, in particular with respect to interdisciplinary research; and to investigate knowledge flows between disciplines. The results show that bibliometric outcomes can offer a test, but also may offer additional information for peer review procedures in science. It also appears that the assumption that peer review is biased in case of interdisciplinary research, is not universally true. An analysis, with the aid of bibliometric methods, of the outcomes of a nation wide research assessment of physics showed no bias in peer review judgements in case of interdisciplinary research programs. In this study a more clear distinction is advocated between interdisciplinarity and societal relevance of research, and furthermore between top down stimulation and bottom up development of interdisciplinarity. This distinction helps to gain more insight into contributions to interdisciplinary developments from within basic research in disciplines. Citation analysis gives indications for the significance of such processes. E.g. citation analysis shows a relatively large knowledge flow from disciplines like basic life sciences and physics to other disciplines. Show less
