Letter in the APS Observer

Michael wrote a brief letter on citation practices, which appears in this month’s APS Observer.

The letter is reproduced below:

I read Roddy Roediger’s recent column on the measurement of journal quality with great interest. As Roddy noted, while “psychologists usually like to think that the behaviors generated by human beings will arrange themselves along a normal curve,” the distribution of citations has a strongly positive skew: most papers are very rarely cited, while a small few are cited often (i.e., if citations items are rank-ordered by frequency, the distribution represents an inverse power function).

One psychological scientist who probably wouldn’t have been surprised by this is George Kingsley Zipf, who discovered that the distribution Roddy noted in citations is ubiquitous in language — so that if you look at the pattern of overall word use in any document or language, it exhibits the same right-skewed pattern of distribution.

One way of thinking about the pattern of behavior Roddy observed is that it is just as we might expect if scientists’ citation behavior obeyed the same principles as other linguistic behaviors.  That is, given what we have read the literature, if we need to cite an article after making point X, the distribution in the literature we have already read means that article Y is the most likely candidate to spring to mind, and so by default we cite Y; which means that the citation simply reproduces and reinforces the existing distribution.

Tellingly, Zipf described his law as the “the principle of least effort” in communication.

Although the relationship between Zipf’s law and the distribution of citations has long been noticed by information scientists (e.g., Liming and Lihua, 1993; Perc, 2010; see also de Solla Price, 1965) the idea of framing the question of what makes papers get cited in terms of the mechanisms underlying the behavior of the people who actually make those citations ought to be of particular interest to psychologists.  While most of us might like to suppose that we behave rationally when it comes to choosing our citations, the statistics imply that a less reflective approach to citations may well be the norm. Assuming that there is actually any substance to these speculations, this in turn raises an interesting question: how are we to weigh the impact of these underlying psychological factors in determining the actual impact of a given journal or article?

— Michael Ramscar
San Francisco, CA

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