Author Co-Citation Analysis (ACA)

Author co-citation analysis (ACA) maps the intellectual structure of a research field by treating authors, rather than documents, as the units of analysis. Introduced by Howard White and Belver Griffith in 1981, ACA rests on a simple premise: when two authors are repeatedly cited together in the same later papers, the community of citers is signaling that their work is intellectually related. By counting these co-citations across a body of literature, assembling them into an author-by-author matrix, converting that matrix into similarities, and projecting it into a low-dimensional map, ACA recovers the 'specialties' or schools of thought that organize a discipline and shows how they relate to one another. White and McCain's 1998 study of information science, which mapped 120 leading authors over more than two decades, became the canonical demonstration of the method and established its workflow.