Scientific papers published in online journals that are open-access have a bigger impact and are cited more frequently than papers readers must pay for, according to a new study.
The findings will strengthen calls for more online scientific journals to switch to the open-access model and make research freely available.
Journal subscriptions are too expensive for many scientists in developing countries, making open-access their sole means of keeping up to date with research in the rest of the world.
The author of the study, published this week (15 May) in PloS Biology, concludes that, "open-access is likely to benefit science by accelerating dissemination and uptake of research findings".
Gunther Eysenbach, a health policy specialist at the University of Toronto, Canada, monitored the number of times each of 1,500 papers published in the Proceedings of the National Academy of Sciences were cited in later studies.
The journal has a 'hybrid' publishing model, meaning that authors can choose to pay a US$1,000 fee to publish their papers for immediate free access on the journal's website. All other papers become open-access six months after publication.
Eysenbach found that open-access papers were twice as likely as other papers to be cited 4-10 months after publication. This increased to three times as likely 10-16 months after publication.
More surprisingly, the study found that articles published as open-access from the start on had a higher impact than articles published as non-open-access, which researchers had 'self-archived' on other websites.
Eysenbach says this could be because few scientists search the Internet for an article if they have encountered problems viewing it on the journal website.
Subbiah Arunachalam of the M. S. Swaminathan Research Foundation in India says, however, that self-archiving is the best approach, even though many journals waive the open-access fee for developing country authors.
"I believe that open-access archiving is a better option because it would allow us to achieve 100 per cent open-access more quickly," he said in an interview published on 10 May on technology journalist Richard Poynder's web blog, Open and Shut?
Eysenbach is editor of the open-access Journal of Medical Internet Research.