PhD research
Citations: how reliable are they?
Citations are used more and more as a measure of scientific quality or impact. But how reliable are they? According to Norwegian PhD Student Dag Aksnes, peer review must remain the primary method of evaluating scientific performance. He defended his thesis last week at the faculty of Business and Technology.
To scientists, it is incredibly important to get high citation scores, because these scores are used as indicators in the evaluation of scientific policy and research. `They also give scientists a certain prestige,' Dag Aksnes explains. `They indicate your work is appreciated.'
Aksnes (35) is affiliated with the Norwegian Institute for Studies in Research and Higher Education (NIFU STEP) in Oslo and did most of his research there. However, he will get his degree in Twente at the faculty of Business and Technology. His promoter is Professor Arie Rip, who has connections with the Oslo institute.
It is common knowledge for scientific researchers that citation scores do not measure the quality but the impact of a publication. Aksnes: `Quality is a multi-dimensional concept. Citations mostly indicate the influence a certain article had. That is why you can never go by citations alone.'
In his thesis, Aksnes examined the reliability and the validity of citation indicators. He was especially intrigued by the skewed distribution of the indexes. `Some articles are cited many, many times but most of them are hardly cited or not cited at all.' Aksnes focused on data about Norway. In some fields of Norwegian science, five articles out of a total output of more than a hundred articles were responsible for about half the citations. Aksnes: `Some contributions encompass an important scientific breakthrough that is cited time and time again, other articles fill in the details and get less attention. That obviously influences the citation average.'
According to Aksnes' research, these commonly cited articles are often written by a large group of international authors. `Articles with international co-authors produce significantly more citations than articles by only Norwegian authors. This increased impact could be caused by the high visibility of an international cooperation. However, it could also be the other way around: perhaps the best and most respected scientists are the ones who write a lot of articles with international co-authors.'
Aksnes concluded that citation scores give at least some indication of the influence of a certain publication. `But considering the limitations, they are best used in addition to peer review.'
Trans. Jeroen Latour
Jannie Benedictus |
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