End of PLoS Exchange

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Update Jan 1, 2010: See Gargouri, Y; C Hajjem, V Larivière, Y Gingras, L Carr,T Brody & S Harnad (2010) “Open Access, Whether Self-Selected or Mandated, Increases Citation Impact, Especially for Higher Quality Research”
Update Feb 8, 2010: See also "Open Access: Self-Selected, Mandated & Random; Answers & Questions"

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PLoS seems to have concluded that it is not in their interest to host further public contributions to the Eysenbach debate from me -- and perhaps they are right (that it is not in their interest)...

From: plos AT plos.org
Date: May 19, 2006 3:13:07 PM EDT (CA)
To: Stevan Harnad harnad AT ecs.soton.ac.uk
Subject: e-Letter: Decision

Unfortunately we decided not to accept your e-Letter. Letters are published at the editors' discretion, and we publish only those that we believe will contribute substantially to the debate. Our editorial decisions about publishing letters are final, and are not open to appeal.

Below is appended the mercilessly compressed fragment that I had submitted to PLoS as a follow-up letter (responding to Eysenbach's PLoS letter responding to my PLoS letter responding to his PLoS article).

The full version of my reply of course appeared on AmSci and in my Archivangelism blog -- but, as Eysenbach's study showed, one gets still further visibility from appearing on the website of a high-profile, high-impact journal! My (valid) rebuttal to Eysenbach's suggestion that self-archiving is to OA publishing as handing out leaflets is to publishing in a newspaper was that we are talking about publications in the case of OA, not unpublished materials! But with a letter, it's more like handing out leaflets when it just appears in a Forum or a Blog, versus the website of a high-impact journal...

Never mind. The content is what matters, and time is on OA's side (even if it is much too dilatory!), because OA is (you've heard the song!): Optimal and Inevitable.

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Confirming the Within-Journal OA Impact Advantage

(Click for Fuller version)

Given the large within-journal OA citation impact advantages repeatedly found across all journals, disciplines and years in samples four orders of magnitude larger than Eysenbach's, it is not clear that controls for "multiple confounders" are needed to demonstrate the reality, magnitude and universality of the OA advantage. (This does not mean Eysenbach’s controls are not useful, just that they are not yet telling us much that we don't already know.)

Eysenbach (and PLoS) are focussed on gold-OA journals; most other OA impact studies are focused on OA itself. Only ~10% of journals are gold today. Few as yet offer authors "Open Choice" (allowing gold within-journal OA/NOA comparisons) and few authors are as yet choosing paid OA.

Regarding the “arrow of causation: yes, “longtitudinal cohort” data would demonstrate causation (for skeptics who think the OA advantage might be a self-selection bias) but Eysenbach's author self-reports certainly aren’t such data! Meanwhile: (a) the OA advantage does not diminish for younger articles; (b) OA increases downloads; (c) increased downloads in the first 6 months correlate with increased citations later; (d) unaffordability reduces access; (e) access is a necessary condition for citation.

About OA being a “continuum” or “spectrum”: Time is certainly a continuum, and access certainly admits of degrees (access may be easier/harder, narrower/wider, cheaper/dearer, longer/shorter, earlier/later, partial/full) -- but Open Access does not admit of degrees (any more than pregnancy does). OA is defined as: full-text online access, free for all.

Eysenbach likens self-archiving to “printing something on a flyer and handing it out to pedestrians on the street [instead of] publishing an article in a national newspaper." But it is published articles that are being self-archived.

NOA (Not OA): 1159 articles (86.2% cited at least once)
POA (Payed OA only): 176 (94.3%)
SOA (Self-Archived OA only): 121 (90.1%)
BOA (POA and SOA): 36 (97.2%)

In this PNAS sample, POA, SOA and BOA together, and POA alone, all have significantly more citations than NOA, but SOA alone ("stratified") does not; also, both POA and SOA increase citations, but POA does it more.

Three possible hypotheses explaining the BOA>POA>>SOA>NOA outcome:

H1: The POA advantage might be a multiple-archiving effect, maximal for high-profile , 3-option (POA, SOA, NOA) journals like PNAS because POA articles are more visible than SOA. (POA + SOA = BOA highest of all: redundancy helps!) As Institutional Repositories fill, this extra advantage will disappear.

H2: The POA advantage might arise in part from self-selection because the decision to pay for POA is influenced by the author's sense of the potential importance (hence impact) of his article. (But I think self-selection quality-bias is just one of many contributors to the OA advantage itself, not the only one or the biggest.)

H3: The POA advantage might be either a small-sample chance result or a temporary side-effect of the 3-option journals in early days: a one-stop shopping advantage for PNAS articles, in a high-profile store, today. It needs to be tested for replicability and representativeness in larger samples of articles, journals, and time-bases.

The true measure of the SOA advantage today is not found in PNAS but in the far more populous and representative full spectrum of journals not yet offering POA. (I’d be delighted if those journals took Eysenbach’s findings as a reason for offering a POA option! But not at the expense of authors wrongly inferring that for the journals they currently publish in, SOA alone would not confer citation advantages at least as big as the ones we have been reporting.)

Harnad & Brody (2004)
Brody et al (2005)
Hajjem et al (2005)

Stevan Harnad
American Scientist Open Access Forum