Citations to highly-cited researchers by their co-authors and their self-citations: How these factors affect highly-cited researchers' h-index in Scopus

The h-index is one of the recent indicators in the field of scientometric which introduced by Jorge Hirsch and measures both the productivity and impact of scholars' work. It has been widely used to show the relevance of the research work of prominent scholars. But, does h-index really show this relevance? The purpose of this study is to investigate the frequency of citations to highly-cited researchers by their co-authors, as well as to quantify the weight of self-citations of highly-cited researchers' in three fields of science: clinical medicine, computer science, and economics & business. Finally, we seek to evaluate the impact of these two elements on their h-index in the Scopus database. In this research, highly-cited researchers were selected from the three fields via HighlyCited.com. The study population includes 999 highly-cited researchers in these three fields (280 authors in clinical medicine, 373 authors in computer science, and 346 authors in economics & business). The results show that the average rate of self-citations and co-author citations in clinical medicine is more than computer science, and in computer science is more than economics & business. The results show that there is a positive correlation between self-citation and total citations (P<0.01) in these three fields. The results also show that there is a positive correlation between "co-author citations" and total citations (P<0.01). Moreover, there is a positive correlation between self-citations and h-index of highly-cited researchers as well as co-author citations and h-index of highly-cited researchers in the above-mentioned three fields. It is seen that there is a significant difference in self-citations behavior and co-author citation behavior in different fields which relates to subject context. Co-author citation is an indicator which, on the one hand, not under control of own researcher and, on the other hand, represents the structure of scientific communications. Although the number of citations is not necessarily increased by raising the number of authors, but co-author citations increased by raising the number of co-authors.