Co-Citation Analyses of Science: An Evaluation

For the past several years, Henry Small and collaborators1 have been arguing strongly on behalf of the utility of a technique called 'co-citation analysis' as a tool for understanding the specialty structure of science. Data which we have collected over the past two years on a specialty in elementary particle physics, the study of weak interactions,2 allow an evaluation of co-citation analysis, and we report the results in this Note. A series of claims for the technique of co-citation analysis have been made by Small and his colleagues. The first and most important claim is that co-citation clusters 'reflect the . . . cognitive structures of research specialties.'3 A second claim is that the 'current population of publishing specialists is . .. the group of citing authors for the cluster.'4 In other words, by using the Science Citation Index (SCI) to identify a cluster of papers which are then held to represent a narrow subject matter grouping or specialty, one can get back to the population of authors in the specialty as a whole by discovering who cites at least one pair of the papers in the cluster for a given year. A third claim, related to the second, is that 'using the same thresholds each year the growth of the specialty can be gauged in terms of the growth of the cluster.'5