Co-citation is the frequency with which two documents are ''

cited A citation is a reference to a source. More precisely, a citation is an abbreviated alphanumeric expression embedded in the body of an intellectual work that denotes an entry in the bibliographic references section of the work for the purpose of ...

'' together by other documents.. If at least one other document cites two documents in common, these documents are said to be ''co-cited''. The more co-citations two documents receive, the higher their co-citation strength, and the more likely they are semantically related. Like bibliographic coupling, co-citation is a

semantic similarity Semantic similarity is a metric defined over a set of documents or terms, where the idea of distance between items is based on the likeness of their meaning or semantic content as opposed to lexicographical similarity. These are mathematical tools ...

measure for documents that makes use of citation analyses. The figure to the right illustrates the concept of co-citation and a more recent variation of co-citation which accounts for the placement of citations in the full text of documents. The figure's left image shows the Documents A and B, which are both cited by Documents C, D and E; thus Documents A and B have a co-citation strength, or co-citation indexJeppe Nicolaisen, 200
Co-citation
, in Birger Hjørland, ed.

from The Royal School of Library and Information Science (RSLIS), Copenhagen, Denmark. of three. This score is usually established using

citation index A citation index is a kind of bibliographic index, an index of citations between publications, allowing the user to easily establish which later documents cite which earlier documents. A form of citation index is first found in 12th-century Hebr ...

es. Documents featuring high numbers of co-citations are regarded as more similar. The figure's right image shows a citing document which cites the Documents 1, 2 and 3. Both the Documents 1 and 2 and the Documents 2 and 3 have a co-citation strength of one, given that they are cited together by exactly one other document. However, Documents 2 and 3 are cited in much closer proximity to each other in the citing document compared to Document 1. To make co-citation a more meaningful measure in this case, a Co-Citation Proximity Index (CPI) can be introduced to account for the placement of citations relative to each other. Documents co-cited at greater relative distances in the full text receive lower CPI values.Bela Gipp and Joeran Beel, 200
"Citation Proximity Analysis (CPA) – A new approach for identifying related work based on Co-Citation Analysis"
in Birger Larsen and Jacqueline Leta, editors, Proceedings of the 12th International Conference on Scientometrics and Informetrics (ISSI’09), volume 2, pages 571–575, Rio de Janeiro (Brazil), July 2009. Gipp and Beel were the first to propose using modified co-citation weights based on proximity.Kevin W. Boyack, Henry Small and Richard Klavans, 201
"Improving the Accuracy of Co-citation Clustering Using Full Text"
Journal of the American Society for Information Science and Technology, Volume 64, Issue 9, pages 1759–1767, September 2013 Henry Small and Irina Marshakova are credited for introducing co-citation analysis in 1973. Both researchers came up with the measure independently, although Marshakova gained less credit, likely because her work was published in Russian. Co-citation analysis provides a forward-looking assessment on document similarity in contrast to Bibliographic Coupling, which is retrospective. The citations a paper receives in the future depend on the evolution of an academic field, thus co-citation frequencies can still change. In the adjacent diagram, for example, Doc A and Doc B may still be co-cited by future documents, say Doc F and Doc G. This characteristic of co-citation allows for a dynamic

document classification Document classification or document categorization is a problem in library science, information science and computer science. The task is to assign a document to one or more classes or categories. This may be done "manually" (or "intellectually") ...

system when compared to Bibliographic Coupling. Over the decades, researchers proposed variants or enhancements to the original co-citation concept. Howard White introduced author co-citation analysis in 1981. Gipp and Beel proposed Co-citation Proximity Analysis (CPA) and introduced the CPI as an enhancement to the original co-citation concept in 2009. Co-citation Proximity Analysis considers the proximity of citations within the full-texts for similarity computation and therefore allows for a more fine-grained assessment of semantic document similarity than pure co-citation.

Considerations

The motivations of authors for citing literature can vary greatly and occur for a variety of reasons aside from simply referring to academically relevant documents. Cole and Cole expressed this concern based on the observation that scientists tend to cite friends and research colleagues more frequently, a partiality known as ''

cronyism Cronyism is the spoils system practice of partiality in awarding jobs and other advantages to friends or trusted colleagues, especially in politics and between politicians and supportive organizations. For example, cronyism occurs when appointin ...

''.Cole, J. R. & Cole, S., 1973. "Social Stratification in Science". Chicago, IL: University of Chicago Press. Additionally, it has been observed that academic works which have already gained much credit and reputation in a field tend to receive even more credit and thus citations in future literature, an observation termed the ''Matthew effect'' in science.

References

{{reflist Citation metrics

Considerations

See also

References