"If I have seen further," claimed Isaac Newton, "it is by standing on the shoulders of giants." The key to comprehending such amazing vistas by all researchers is science's incrementalist tradition of building phenomenon-explaining grand theories finding by finding as facts accumulate across decades of previous research. In the past dozen years or so scientists have increasingly turned toward "open access" (OA) publication, where full-text articles, research results or complete journal issues are freely available online, rather than accessible only to subscribers who pay for a subscription, as a way to make these metaphorical giants' shoulders more widely accessible.

Historically, journals were mainly subscriber-supported, but high fees have made subscriptions prohibitive to many universities (let alone individuals) in the U.S. and abroad. In the past decade a new model has emerged. Some journals are now free to all, but the authors who publish their research in the volumes must pay a fee—often upward of $2,000. Currently, more than 5,600 OA journals are published around the world, and 8.5 percent of all scientific journals are estimated to be open. (The only major scientific publisher that is entirely open-access is the Public Library of Science, which produces the seven PLoS journals.) Much of the OA literature consists of individual articles that are made accessible either through a university database that can be accessed by anyone with sign-on privileges to that network or through standard subscription journals. If the trend continues, more of the major research journals may become open-access in the next decade, which should make scientific knowledge more accessible and advances happen more quickly. At least that is the hope and claim of OA advocates.

Dan Lee, director of the Office of Copyright Management and Scholarly Communications at the University of Arizona in Tucson, argued on November 2 that open-access publication of research articles and papers is key to the advancement of scientific creativity and innovation. "Without the barrier of subscription," Lee said, "the information is just out there on the Web and available to you. You get more research done if there aren't barriers to accessing previous research."

Such salutary claims of OA proponents are supported, at least in part. In the past several years Bo-Christer Björk of the Hanken School of Economics in Helsinki and Elena Giglia, a librarian at the University of Turin, have published research showing that OA articles are more widely read and cited than non-OA research. An article's number of citations is a rough measure of a finding's impact. Funding agencies such as the National Institutes of Health and major universities including Harvard, Cornell and the University of California, Berkeley, have all recently instituted policies that all research be made freely available.

And a recent study, led by Stevan Harnad of the University of Québec in Montréal and published on October 18 in PLoS ONE, found that open-access articles have higher citation rates whether the authors voluntarily submit their research to open-access university databases or the submission is mandated by universities and funding agencies. A statement released by PLoS said that "PLoS had no involvement in the research presented in this paper," and that the acceptance of the paper was at the sole discretion of the academic editor who was not affiliated with PLoS.

Harnad and colleagues had hypothesized that more accessible research would be more highly cited, simply because more scientists would have access to the findings. "It's as you would expect—the research is accessible to more potential users," Harnad says. "Scientists are doing research so that it can be used and built upon. They're not writing up their results just to make money," he adds. Because scientists are not motivated by profit, Harnad believes that open-access won't hurt the primary goal of advancing research. Open access, Harnad argues, opens the door of science to researchers in resource-poor settings and to citizen scientists and interested amateurs.

That door, however, may not be as solid as it seems—even when closed. Philip Davis, in the Department of Communication at Cornell University, says that "it is amazingly easy to move information around." If a researcher doesn't have a subscription to a particular journal, Davis says, they will often just e-mail the author of the article or ask a colleague in another university. "It's not a closed door. It's more of a very porous sieve."

Nor is Davis convinced that OA benefits are as significant as some of the recent research has claimed. Davis headed two previous studies, the most recent of which was a randomized control trial for OA research. In 11 different physiology journals Davis's group randomly allocated research articles to be published OA or not, and tracked their usage and citations. The results, published in 2008 in the British Medical Journal, found that although OA articles were downloaded more frequently they were not cited significantly more than non-OA articles.

These results leave Davis reluctant to support the recent trend of both funding agencies like the National Institutes of Health and universities mandating that research results be made open-access. "Science policy should be supported by rigorous research," Davis says, and the research thus far is not rigorous enough to support policy that dictates open-access publishing.

Although it remains to be seen whether U.S. science policy will mandate all research be made open-access on publication, the amount of OA research is rapidly increasing, according to Mark Patterson, director of publishing at PLoS. "More and more publishers are launching new open-access journals," Patterson says. "It's definitely an established part of the publishing landscape now." Even in just the past few months the American Society for Microbiology has launched the open-access online journal, mBio, and Springer Publishing created a new line of OA journals called SpringerOpen.

Despite their areas of disagreement, both those for and against mandating that published research be freely available see science as a collaborative and open effort. "I view science as a distributed, grassroots endeavor," Davis says. "I don't see any one group or government or authority controlling science."