In a few days' time, a collaborator is going to be giving a talk to our research group. He has sent me the slides in advance (just to check that it all runs OK on our system). Having looked over the slides, I have noticed a mistake in his methods (a major assumption that is not just unsupported, but definitely incorrect) that unfortunately invalidates his entire analysis. This mistake is potentially fixable, but only by going back to square one, and the new analysis could (and I suspect probably will) yield different results.

Obviously, I need to raise this with him, but when is the most tactful time to do this? My concern is that if I raise the problem immediately, it leaves him with too little time to redo the analysis before his presentation, and leaves him stewing over it knowing that his prepared work is invalid. Also, I wasn't specifically asked to give feedback at this stage. On the other hand, if I leave it until the talk, it means that I have to bring it up in front of the rest of the research group, and he has no time to prepare a response.

I feel like both situations leave me looking cruel. Which option is preferable, or is there an alternative approach that I've not thought of?

[And to anticipate the comments, I am 99% sure that there is an important mistake and that it's not just my misinterpretation]

  • Does your collaborator's talk concern the work you've done collaboratively? Jun 3, 2016 at 17:57
  • 3
    Tell him ASAP and let him decide what to do. Would you rather be blindsided during or after a presentation or find out about it beforehand?
    – mkennedy
    Jun 3, 2016 at 18:03
  • @PeteL.Clark We're both working on different aspects of the same overall project but have not worked together on the particular question addressed in the talk. Jun 3, 2016 at 18:05

1 Answer 1


On the other hand, if I leave it until the talk, it means that I have to bring it up in front of the rest of the research group, and he has no time to prepare a response.

Not necessarily. You have the option of bringing it up with your collaborator privately, after the talk. In general, a talk is not the ideal time to figure out whether the work presented is correct: that makes things stressful for the presenter, and unless the group is small and well-chosen, likely there will be some people there who are not invested enough / do not have enough background to want or be able to follow such a discussion.

If you talk to your collaborator afterwards, then this is less awkward in case you are mistaken or there is some kind of misunderstanding. (In my experience, a lot of perceived mistakes in other people's work turns out to be some kind of misunderstanding.) If you are right, you can still offer him help to fix the problem, in a way which might not work in the context of a talk. In particular, in order to recognize and correct the error your collaborator will likely have to stop and think for more than a minute or two, which is the one thing that is almost impossible in a talk.

Maybe you feel bad having a talk in your research group that you strongly suspect is wrong. Well, certainly if it turns out to be wrong that information will be conveyed to the group: your collaborator can send out new slides, a new paper, and so forth. Moreover, just because the results are flawed doesn't necessarily mean the talk itself isn't worthwhile: it still may be.

It could be that you feel strongly that the material is so flawed that it is not worth subjecting your research group to a talk about it. That's a tough situation. Fortunately you've collaborated with your collaborator, so you may have some insight into how he would behave if he learned a few days before his talk that you think his results are seriously flawed. If you've given this kind of negative feedback to him before and he's reacted well, I would risk it and let him know ASAP what you think is wrong. If he agrees, maybe offer him the opportunity to reschedule.

For what it's worth, here's one data point: if someone that I worked with found what they thought was a flaw in my work, I would like them to tell me immediately. I would much rather cancel a talk then give a talk that I later found out was wrong, and if given a few days' notice I would probably just switch to something else.

  • 1
    I don't know about the first paragraphs...As you later say yourself, you'd rather know beforehand. I would too. On top of a small chance to correct what's wrong in this short time, I'd think it more likely that the department invited a person they like and value, not so much for them to talk about a particular topic. That's not certain, but, to me, more likely to be true than not. There might be an interesting alternative talk they could suggest giving, admitting to having to work out some issue in the planned talk that was noticed. So I'd let them know as soon as possible. Jun 3, 2016 at 18:30
  • @gnome: What I was pointing out here is that the OP has the option of bringing it up after the talk. He asked for options. If the OP doesn't know his collaborator well or knows him to be prickly when it comes to this sort of thing, he could create an awkward situation by bringing it up in advance. Also, my answer applies to me now. We didn't do powerpoint presentations when I was a student, but I can imagine that if I were a rather young student talking about my research, hearing that it was all wrong a few days before might freak me out. It can be nicer to hear this news in person. Jun 3, 2016 at 18:52
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    Perhaps the real takeaway from my answer is: standing up in the middle of the talk and saying "J'accuse!" has got to be the worst way to play it. Jun 3, 2016 at 19:15

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