Stevan Harnad
Chaire de recherche du Canada
Centre de neuroscience de la cognition (CNC)
Institut des sciences cognitives (ISC/CSI)
Université du Québec à Montréal
Montréal, Québec, Canada H3C 3P8
and
Department of Electronics and Computer Science
University of Southampton
Highfield, Southampton
SO17 1BJ UNITED KINGDOM
http://www.ecs.soton.ac.uk/~harnad/
I
applaud and welcome the results of the Eysenbach (2006)
study on 1492 articles published during one 6-month period in one
journal (PNAS), showing that the
Open Access (OA)
articles were more cited than the non-OA ones. I also agree fully that
the
findings are unlikely to have been an artifact of PLoS's "strong and vested interest in
publishing results that so obviously endorse our
existence," nor of the fact that "the author of the article is also an
editor
of an open-access journal" (all quotes are from the PLoS
Biology
editorial by MacCallum
& Parthasarthy, 2006).
However,
I am less sure that PloS's and the author's vested
interests are not behind statements (in both the accompanying editorial
and the
article itself) along the lines that: "solid evidence to support or
refute...
that papers freely available in a journal will be more often read and
cited
than those behind a subscription barrier... has been surprisingly hard
to find."
The online bibliography 'The effect of open access and downloads
('hits') on
citation impact' http://opcit.eprints.org/oacitation-biblio.html
records a growing number of studies reporting precisely such evidence
as of
2001, including studies based on data from much larger samples of
journals,
disciplines and years than the PloS study on PNAS... and they all find
exactly
the same effect: freely available articles are read and cited more.
There
can be disagreement about what evidence one counts as "solid," but
there can be little dispute that prior evidence derived from
substantially larger
and broader-based
samples
showing substantially the same outcome can hardly be described as
"surprisingly
hard to find."
In
fact, the only new knowledge from this small, journal-specific
sample was (1) the welcome finding of how early the OA advantage can
manifest
itself, plus (2) some less clear findings about differences between
first- and
last-author OA practices, plus (3) a controversial finding that will
most
definitely need to be replicated on far larger samples in order to be
credible: "The analysis revealed that self-archived articles are also
cited less often
than OA articles from the same journal."
The
latter (3) is a within-journal (one journal, PNAS) finding;
the overwhelming majority of self-archived articles today (on which the
prior
large-sample OA citation advantage findings are based) do not appear in
journals with a paid-OA option. Hence on the present evidence I have
great
difficulty in seeing this secondary advantage as any more than a
paid-OA
publisher's pipe-dream at this point.
The
following, however, is not a pipe-dream, but a peccadillo: "no
other study has compared OA and non-OA articles from the same journal."
To be
fair, this observation is hedged with "[a]s far as we are aware" (but
the OA-advantage
bibliography is surely public knowledge -- or should be among
advocates of
public access to science) and the observation is further qualified
with: "and
[also] controlled for so many potentially confounding factors."
But it has to be stated that of
these "potentially confounding"
variables -- "number of days since publication, number of authors,
article
type, country of the corresponding author, funding type, subject area,
submission track (PNAS has three different ways that authors can submit
a
paper)... previous citation record of the first and last authors...
[and] whether
authors choosing the OA option in PNAS chose to do so for only their
most
important research (they didn't)" -- many are peculiar to this
particular short-interval,
3-option, single-journal PloS study. And several of them (country,
subject,
year) had already been analyzed
in papers that had been published before this 2006 article and were not
taken
into account despite the fact that both their preprints and their
postprints
had been freely accessible since well before publication, and that at
least one
of them (Brody et al. 2005) had been explicitly drawn to the author's
attention
based on a preprint draft well before the article was submitted to
PloS.
Brody et al. (2005) had found that, alongside the OA citation advantage, more downloads in the first six months after publication are correlated with more citations 18 months later in physics; and Hajjem et al. (2005) had found higher citations for OA articles -- comparing always within the very same journal and year -- for 1,307,038 articles published across 12 years (1992-2003) in 10 disciplines (Biology, Psychology, Sociology, Health, Political Science, Economics, Education, Law, Business, Management).
Brody,
T., Harnad, S. and Carr, L. (2005) Earlier Web Usage
Statistics as Predictors of Later Citation Impact. Journal of the American
Association for Information Science and Technology (JASIST) 56. http://eprints.ecs.soton.ac.uk/10713
Eysenbach,
G, (2006) Citation Advantage of Open Access Articles.
PLoS Biology 4(5): e157 DOI:
10.1371/journal.pbio.0040157 http://dx.doi.org/10.1371/journal.pbio.0040157
Hajjem,
C., Harnad, S. and Gingras, Y. (2005) Ten-Year
Cross-Disciplinary Comparison of the Growth of Open Access and How it
Increases
Research Citation Impact. IEEE Data
Engineering Bulletin 28(4) pp. 39-47. http://eprints.ecs.soton.ac.uk/11688/
MacCallum,
C.J., and Parthasarathy, H. (2006) Open Access
Increases Citation Rate. PLoS Biology
4(5): http://dx.doi.org/10.1371/journal.pbio.0040176