Quantifying the interdisciplinarity of scientific journals and fields

nals and fields. Filipi N. Silva1, Francisco A. Rodrigues2, Osvaldo N. Oliveira Jr, Luciano da F. Costa1,3† There is an overall perception of increased interdisciplinarity in science, but this is difficult to confirm quantitatively owing to the lack of adequate methods to evaluate subjective phenomena. This is no different from the difficulties in establishing quantitative relationships in human and social sciences1. In this paper we quantified the interdisciplinarity2 of scientific journals and science fields by using an entropy measurement3, 4 based on the diversity of the subject categories of journals citing a specific journal. The methodology consisted in building citation networks using the Journal Citation Reports database, in which the nodes were journals and edges were established based on citations among journals. The overall network for the 11-year period (1999-2009) studied was small-world5 and scale free6 with regard to the in-strength. Upon visualizing the network topology an overall structure of the various science fields could be inferred, especially their interconnections. We confirmed quantitatively that science fields are becoming increasingly interdisciplinary, with the degree of interdisplinarity (i.e. entropy) correlating strongly with the in-strength of journals and with the impact factor.