Eysenbach is very careful to point out that this study needs to be repeated. His study is limited to one (high quality) journal and covers a relatively narrow time frame (from 0 to 16 months after publication). He is right, of course.
Also, he may not have included all confounding variables. For instance, I have not seen a correction for self-citations, which might be relevant here, because OA articles tend to have more authors.
As Eysenbach points out too, the journal studied can be accessed by almost anyone working for a university - that is, most universities pay for access. This leaves us with one nagging question: what the hell IS the cause of the OA effect? A nice supplement to this study would have been to find out why the citing authors did prefer OA articles. Is the difference caused by authors who, for some strange reason, do not have access to the non-OA articles? Is it a matter of convenience (are they accessing the articles from home and is access there more problematic)?
And why is there no bonus effect for self-archived articles?
PS: Is it true that OA articles tend to have more authors? I've never seen evidence one way or another about that.
Posted by
Peter Suber at 5/16/2006 01:43:00 PM.
The open access movement:
Putting peer-reviewed scientific and scholarly literature
on the internet. Making it available free of charge and
free of most copyright and licensing restrictions.
Removing the barriers to serious research.
I recommend the OA tracking project (OATP) as the best way to stay on top of new OA developments. You can read the OATP feed on a blog-like web page or subscribe to it by RSS, email, or Twitter. You can also help build the feed by tagging new developments you encounter.
