Recently, various people have asked me -- in person or by email -- about what to include or not include in an interview talk (or talks) in the specific case in which you have many possible things to talk about.
Even if your only talk-worthy research experience to date has been your graduate work, your research may have been sufficiently complex and multi-faceted that you are faced with a major decision about what to talk about. Things get even more interesting when you have had various research experiences (e.g., grad school + postdoc(s)) and have an even bigger decision about which research projects to talk about in an interview presentation. Perhaps it is obvious that one research project is the #1 best topic for a particular job, but what if it's not obvious? How do you decide what to talk about?
Although having various projects might make for a more complicated decision, having these options can result in a very interesting talk. I worked on very different things for my postdoc and graduate research, and I found that the interview talk that worked best for me (and was most fun to give) involved bits of both projects.
I was discussing this recently with a former student who has an upcoming interview at Awesome University and who had to make a similar decision about what to include in the interview talks. She will be giving two talks as part of the interview, and was considering talking about Project A in one talk and Project B in another talk.
My advice, which may or may not have been helpful or even good, is not to divide the research so neatly. I think it would be much more interesting to do a bit of integration of the commonalities of the two projects. Perhaps I am biased because I found that this worked well for me, but I think it will also be effective in this case.
In the case of one talk and two projects, you can do a bit of integration, then focus specifically on the project that is most relevant and/or cool.
If you have two talks and at least two projects, Talk 1 can still mostly be Project A and Talk 2 can mostly be Project B -- it is important to give a coherent talk, after all -- but if you can successfully integrate some elements of different projects in a Big Picture kind of way, then you show your audience (and the hiring committee) that you are driven by first-order questions and can see broad connections among topics and methods.
If you have two talks and one project.. that's tricky, but perhaps one of your talks will be a general talk and one will be more specific, so you can talk about your one project in different levels of detail.
Being able to integrate components of different projects is a useful skill in general, and is an approach you can take throughout your career when giving invited talks about topics that may touch on various projects with which you are involved. It can be difficult to do, but that's just part of the fun.
10 years ago