I never had a Research Assistantship (RA) when I was a grad student. I had a Teaching Assistantship (TA) my entire graduate career. I was lucky enough to get teaching jobs in the summer as well, so I never lacked for funding. In my grad program, TA's were definitely second class citizens compared to RA's. We were expected to get just as much research done as the RA's, but we had all these other responsibilities as well. In addition, RA's got the best offices and were favored for awards and fellowships, I suppose the thinking was that because these students were RA's, they must be great(er).
This situation didn't bother me too much. I didn't like that I was given the lowest priority in the analytical labs, despite having a more restricted schedule than the RA's, but in the end, I felt that I got more respect for being a successful TA and researcher. This only happened during the final year of my grad career though.
At one point, doing the successful TA-research thing backfired on me: my advisor told me that he had considered rewarding my productivity with an RA, but then it occurred to him that being a TA would slow down his RA's, but it wouldn't slow me down, so he decided I should continue to be a TA. So I did, but it paid off. He wrote me an awesome letter of reference, which I didn't see, but which someone later told me had a nice part in it about my ability to balance teaching and research. This letter was important in my getting a faculty position. The year I got my first tenure-track job, there was only one position in my field available at a research university. When I got the job offer, the hiring committee told me that my extensive teaching experience gave me an edge over the candidates who had never taught before.
Also, my teaching as a grad student led me to collaborations involving education-related activites. I have maintained some of those connections and activities for decades, and it's an interesting and important part of my career.
Nowadays, I don't think TA's are valued less than RA's. At least, not in my department. Education has become such an important part of the mission of research universities, and it is well known that grad students need broad training in research and teaching. Most of my grad students do some of both. I try to give my students a mix of RA and TA depending on their interests, abilities, career plans, and grad program schedules. When one of my RA's finds his or her research a burden and has trouble finding time to get results, I am always amazed. I've never told my students that I was never an RA. It would sound too much like saying "When I was your age, I walked 17 miles through snowy monster-infested woods to get to school..".
I'm sure it affects my advising philosophy somehow though, or at least accounts for my difficulty being sympathetic when an RA doesn't function well.
I should say, just to end on a positive note, that when an RA does function well, as my current group of students do, it is really amazing. For one recent proposal, one of my grad students helped provide the preliminary data and participated in the writing, and when it was funded, he was justifiably extremely proud. Now he gets to do all sorts of interesting new things with his research, he is totally funded for the rest of his grad career, and he's doing really well. When it's time for him to apply for jobs, I will prominently state in my letters that he has participated in a major way in writing a successful NSF grant proposal. Win-win.
7 months ago