A problem I often encounter is deciding who to invite as co-authors. On one hand, you want to show appreciation to the people that helped you in the process of obtaining your results. On the other hand, generously adding authors will dilute the contribution of the people that made the largest contribution. In this post I would like to sketch a few hypothetical situations in which someone could be a co-author. The main goal here is to provoke some discussion on this subject, and learn about some good practices.

Undergraduate students

As a first example, I would like to take undergraduate students. From acquaintances in other disciplines than physics (psychology, medicine, pharmacy) I heard that it is rather uncommon to have undergraduate students as co-authors. An important reason is that many students are involved in the project, and including them on a paper would drastically increase the number of authors.

In my research however, I feel they often greatly contribute to the research. First, they do work that is otherwise not done, e.g. some wild new idea that can be explored. Second, they are often involved in many discussions, which may give new insights. Hence, if they were part of the project I would be inclined to ask them as co-author. On the other hand, some undergraduate students only do what they are told. If they are lucky, and some nice results come out, should they still be co-author? I would guess not.

Specialists

Another interesting group of people is specialists. For example, someone that makes a crucial sample or someone that performs a specific and important measurement that you cannot do yourself (easily). Typically these people are not part of the entire of the research. Should these people be invited as co-authors, if so for how many papers? For example, a sample is made, on which different sets of measurements are performed, that are published separately. I would say that the person who made this sample made a crucial contribution to all papers, and hence should be co-author. However, it is the people who perform the extra measurements, that may put most work (i.e. time) in it. Ad Lagendijk’s survival guide for scientists suggests inviting the specialist as an author for one paper. I think this is rather meager, especially since they are never first authors but often second, third or fourth authors. Secondly, most sample production is so complicated that a lot of time is lost when an inexperienced PhD student does it, instead of the experienced specialist. Hence, the student can obtain more results because of the effort of the specialist.

Former colleagues

The last category is the “almost finished spectacular result”. What happens often is that someone invests his PhD in doing a spectacular and very hard measurement. The plans were too ambitious however, and the student leaves a paved road for his or her successor. The new PhD student has a huge benefit of all the work done, is able to get the job done and obtains the spectacular results that were hoped for. Sometimes, this may even be a series of very interesting results. I think in these cases credits are due to the student who started the project and got it running. Again, I feel this student deserves to be co-author on a number of papers that build on his work. This will, like the case of the specialist, not be first authorships, and therefore some generosity is fair. It is difficult, however, where to draw a line. For me, it should be leading that a student gets a fair amount of papers, compared to the quality of the work.

To finalize this post, I wish to note that all of this would not be a big deal if we would not try to quantify the quality of a scientist using the number of authored papers. This leads to the effect that PhD students already have to worry about the number of papers they write, and the impact factor of the journals they write for.

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