Salami slicing, breaking a paper on a single study up into smaller “slices” and publishing them in more than one journal, is broadly discouraged and considered unethical. Why does the practice persist? What do PIs believe are the benefits of doing it?
Breaking up research into smaller slices can have serious consequences for scientific integrity. Researchers, especially younger researchers, may get used to looking at data in smaller pieces and not as a whole. This is dangerous from an academic perspective as valuable conclusions, that could have been derived if the data were presented as a whole, are overlooked.
Further, salami slicing of data may do more harm than good to a researcher’s career over time because it significantly reduces their chances of publishing in high impact journals, thereby lessening the weight of their accrued body of work.
One reason salami slicing still persists, is that there is a veritable avalanche of papers vying for publication. And the number seems to be steadily increasing.
“The academic market became more competitive after the nation’s economic downturn, in 2008,” said Rodica Damian, UH associate professor of psychology. “We saw a lot of competition between those with Ph.D.s and those who were conducting postdoc research. Before, you needed a postdoc if you were in Biology, for instance – but you didn’t need one if you had a doctorate in Psychology. That is no longer the case.”
Another reason salami slicing might persist is that advisors may suggest to a graduate student that they write a series of simpler papers as opposed to a more complex paper consisting of multiple measurements. A researcher might get these “single-lens papers” published much more quickly than their multi-faceted counterparts, due to the amount of background research the journal’s editors need to do on the more complicated papers.
How to avoid self-plagiarism
Salami slicing is not necessarily self-plagiarism, but often the practice does feature a large amount of “text overlap,” according to Miguel Roig, Ph.D. on the website of the Office of Research Integrity for the U.S. Department of Health and Human Services. One example Roig gives is as follows:
“Several months ago, for example, we received a manuscript describing a controlled intervention in a birthing center. The authors sent the results on the mothers to us, and the results on the infants to another journal. The two outcomes would have more appropriately been reported together…The important point is that readers need to be made aware that the data being reported were collected in the context of a larger study.”
The Big Idea
An article published by the NIH suggests this rule of thumb: “If the ‘slice’ of the study in question tests a different hypothesis as opposed to the larger study or has a distinct methodology or populations being studied, then it is acceptable to publish it separately.”
However, when a colleague is trying to do a meta analysis, they need to know what your study actually measured. “One thing you can do to avoid salami slicing,” said Damian, “is to pre-register all the projects you’re planning to do from a specific data set. Then ask yourself, do they use different hypotheses, measures, literatures, etc.”
After all is said and done, are they substantively methodically different research papers? If so, they can be sent to different, separate journals.