The allocation of credit can also become an issue in the listing of authors' names. Science has become a much more collaborative enterprise than it was in the past. The average number of authors for articles in the New England Journal of Medicine, for example, has risen from slightly more than one in 1925 to more than six today. In some areas, such as high-energy physics or genome sequencing, the number of authors can rise into the hundreds. This increased collaboration has produced many new opportunities for researchers to work with colleagues at different stages in their careers, in different disciplines, or even in widely separated locations. It has also increased the possibility for differences to arise over questions of authorship.

In many fields, the earlier a name appears in the list of authors, the greater the implied contribution, but conventions differ greatly among disciplines and among research groups. Sometimes the scientist with the greatest name recognition is listed first , whereas in other fields the research leader's name is always last. In some disciplines supervisors' names rarely appear on papers, while in others the professor's name appears on almost every paper that comes out of the lab. Some research groups and journals avoid these decisions by simply listing authors alphabetically.

Frank and open discussion of the division of credit within research groups—as early in the research process as possible and preferably at the very beginning, especially for research leading to a published paper—can prevent later difficulties. The best practice is for authorship criteria to be explicit among all collaborators. In addition, collaborators should be familiar with the conventions in a particular field to understand their rights and obligations. Group meetings provide an occasion to discuss ethical and policy issues in research.

The allocation of credit can be particularly sensitive when it involves researchers at different stages of their careers-for example, postdocs and graduate students, or senior faculty and student researchers. In such situations, differences in roles and status compound the difficulties of according credit.

Several considerations must be weighed in determining the proper division of credit between a student or research assistant and a senior scientist, and a range of practices are acceptable. If a senior researcher has defined and put a project into motion and a junior researcher is invited to join in, major credit may go to the senior researcher, even if at the moment of discovery the senior researcher is not present. By the same token, when a student or research assistant is making an intellectual contribution to a research project, that contribution deserves to be recognized. Senior scientists are well aware of the importance of credit in science and are expected to give junior researchers credit where warranted. In such cases, junior researchers may be listed as coauthors or even senior authors, depending on the work, traditions within the field, and arrangements within the team.

Occasionally a name is included in a list of authors even though that person had little or nothing to do with the content of a paper. Such "honorary authors" dilute the credit due the people who actually did the work, inflate the credentials of those so "honored," and make the proper attribution of credit more difficult. Several scientific journals now state that a person should be listed as the author of a paper only if that person made a direct and substantial contribution to the paper. Some journals require all named authors to sign the letter that accompanies submission of the original article and all subsequent revisions to ensure that no author is named without consent and that all authors agree with the final version.

As with citations, author listings establish accountability as well as credit. When a paper is found to contain errors, whether caused by mistakes or deceit, authors might wish to disavow responsibility, saying that they were not involved in the part of t he paper containing the errors or that they had very little to do with the paper in general. However, an author who is willing to take credit for a paper must also bear responsibility for its contents. Thus, unless a footnote or the text of the paper explicitly assigns responsibility for different parts of the paper to different authors, the authors whose names appear on a paper must share responsibility for all of it.