In the framework of a collaborative project (i.e. 10 universities of the same country got granted money to do research using different approaches in the same topic), i was hired to develop a model. This model is not very novel, the novelty lies in coupling several sub-models, which have already been published.
I gave a talk to all the researchers of the project (around 50 people). During my talk, an Associate Professor from another university gave me a very valuable suggestion (I missed something, but it could be fixed just by adding a different sub-model to my model: i.e. changing a couple equations in the formulation). After that, he wrote an email to me and we had a 10 minutes skype discussion.
After submitting the paper 3 months ago, the Associate Professor wrote an email to me saying that he had been invited by the journal to review the paper, something that he rejected due to conflict of interests. In a polite way, he said to me that he considers he should be an author of the paper, as he read the abstract and thinks some ideas are his. In his email, he suggests that not only the idea of changing something was his, but other ideas expressed in the abstract were also his one idea. He tries to be friendly in his email, and he explicitly says that he writes to me and explains this situation, so I do not have this kind of misunderstanding in the future (as I am an early career researcher).
The paper has 5 authors. Me, my supervisor (we did all work) and three "guest authors": the principal investigator of the research grant, the head of the research grant at my university and a PostDoc that continued this research line after I left the University. These three people were not involved in the research.
To me, his reaction is toxic and over-dramatic. He was never involved in the coding and validation of the model, and he never saw a draft of the manuscript. The only two times I talked to him about the model was in the group meeting and in the subsequent skype talk (10 minutes). In my mind, he gave his opinion of the model and gave valuable suggestions on how to improve it. To me, this is the behavior a tenured professor (and expert of that field) should have in the context of a collaborative project between several Universities, without expecting to be added to the authors list. Moreover, my field is so small that, during conferences, other senior academics (with whom I have never talked) have suggested me ideas to work in the future.
My questions are:
To what extent giving a suggestion (even if valuable) in the framework of a collaborative project between universities converts you as a co-author, or adding that person in the acknowledgement is sufficient.
Should I reply to the Associate Professor being political correct (I feel sorry you feel this way, you know I tried to add you as a co-author,….) or being a little confrontational to him (One idea was yours, but you gave it in the framework of a collaborative project; you were never really involved in my research project….)?