Obviously, if you choose to either do a PhD in English literature, or in mathematics, this choice will heavily determine the possible career paths you can later take.

But to what extent does the choice between two different topics within the same discipline influence your career possibilities?

  • Physics: Quantum computing vs high energy particle physics

  • Math: differential topology vs abstract algebra

  • Economics: business cycle theory vs industrial organization.

  • Psychology: Evolutionary psychology vs Neuro-psychology

Would such a choice significantly affect your future career, or is there generally such an overlap in the skills you learn doing different topics that you will be able to easily switch between these topics within the same discipline?

  • 3
    Are we talking about a career in academia, or a career outside academia?
    – user9646
    Commented Apr 3, 2018 at 17:13
  • 6
    I'm generally frustrated by PhD students who think they will spend the next 30 years of their life working on the same thing they did their PhD on. As one example (perhaps extreme) of changing paths, I know a professor who went from low temperature physics of superconductivity to winning the APS prize in polymer physics. The point of a PhD is that you know how to learn and apply relevant techniques to interesting questions and get an answer.
    – Jon Custer
    Commented Apr 3, 2018 at 17:21
  • @JonCuster Amen!!! but generally this is also advisor fault. They r not more open minded
    – SSimon
    Commented Apr 4, 2018 at 1:27
  • 1
    I've heard people at undergrad, grad, postdoc and faculty positions all worry that it is too late to change fields. You can always change if you have the motivation.
    – Bitwise
    Commented Apr 4, 2018 at 9:49

6 Answers 6


Very few people are static in their careers, in and out of academia. My PhD was in the area of molecular simulations in chemical engineering. My post doc was with a physicist working in computational materials, then I took a staff position in environmental engineering doing fluid flow and geochemistry studies, I have since moved into renewable energy applications and biomedical, with side work in algorithm development and kinetics.

All of this is to say, any limits on what direction your career can take are placed by the researcher, not the field of study. If you’re not willing to branch out, your choice of jobs will be limited. If you’re willing to explore, the options are as infinite as your curiosity and salesmanship will allow.

  • I think the one overarching limitation is some jobs need that extra hard qualification. For example, you can go out and get a Ph.D. in Chemistry and have a fulfilling career as general counsel to large pharmaceutical corporations so long as you also get a law degree.
    – CKM
    Commented Apr 3, 2018 at 19:34
  • True. But the question is asking about choice of topic within a field. If you have a chem PhD, it probably doesn’t matter if it’s in synthesis or q-chem.
    – aeismail
    Commented Apr 3, 2018 at 20:49
  • 2
    generally what it seems to be important for chemistry fundraising skills. topic is irrelevant
    – SSimon
    Commented Apr 4, 2018 at 1:30

In the humanities, you may find yourself slightly limited — initially.

For example, if a Shakespeare scholar leaves an English department, depending on how large the department is and its make up, they may look to replace him with another Shakespeare person, a British literature person, an early modernist, or any one in English. If an applied linguist leaves, they will probably try to hire another applied linguist, or if it's a smaller department, just a linguist of the applied or theoretical flavor. (This assumes a department isn't trying to change directions, but in that case they will still have a [sub]field in mind).

If an art department wants a Far East modern art historian, and you are a European modern art historian, you can try to get the position, but may not pass the initial cull of applications, depending on whether the European or modern part is more important. But someone who does specialize in that and gets the job, may begin transitioning towards being a modern Latin American art historian. Then they could justifiably apply for jobs looking for specialists in that but in the meantime would likely be expected to continue teaching courses that they were hired for (and even then things can change).


Picking a Ph.D topic restricts your career choices about as much as picking an airport restricts which countries you can visit.

As Jon Custer notes, having a Ph.D (by research, that is - I've heard of Ph.D by coursework but don't have experience there) is in a sense a certification as an independent thinker. Your work has been reviewed by experts in the field, and they agree that your work is an original and independent advance in your field. Naturally, this gives you a head start in your own field.

Ph.D work tends to be deep and narrow, and somewhat ahead of the curve. Will people be advertising for work based on your specific thesis? It's possible, but very unlikely. So even if you remain in the general field, you should be prepared to work on something different from your thesis anyway.

As an employer working in a tech R&D setting, if I'm looking at prospective staff with a Ph.D, I'd probably want it to be in a maths-based discipline, but the specifics aren't likely to matter too much unless I'm chasing a narrow requirement. Cultural fit and other personal qualities are likely to be more important - including, after a few projects, your track record.


To some extent, if you get a PhD in a field, then that's probably sufficient for a lot of purposes. In some contexts, even the precise field that you got your PhD in isn't a huge issue.

However, yeah, the choice of dissertation project can matter a lot. If you spend years working on a dissertation project, then it's a golden opportunity to get to know that field's community and gain recognition as an expert. You might engage in collaborations that'll eventually define your career, including getting you a job or clients.

It'd seem ideal if you could start on that process from Day 1, doing a dissertation project in something that you'd like to pursue in your later career. However, many PhD students don't know precisely what they want to do long-term, or else they can't find support for such a project, so it's pretty common for PhD students to do projects different from what they'd later pursue.

So it's probably best to say that a PhD's career isn't really restricted by their choice of dissertation project, but rather than a PhD's career can be greatly served by selecting a dissertation project that they'll want to build their career from.


Your choice of PhD topic can give you a slight head-start in a particular career path if it matches well to the work done in that position. However, choosing a topic (as opposed to a discipline) that does not match your later career path does not harm you, except to the extent that it forfeits this small advantage. If you undertake a PhD in a particular discipline (physics, maths, economics, psychology, etc.) you should acquire the ability to learn new topics in that discipline within a shorter time than it would take you to do another PhD in that topic. Hence, once you have completed your PhD in a particular discipline, it is usual that you can move around with reasonable ease, so long as you are willing to put in some time to learn a new topic.

For the most part, your PhD is an accreditation that signals high-level knowledge of a subject area and the ability to undertake research at a level that can be published in peer-reviewed scholarly journals. Most PhD graduates go on to publish papers in scholarly journals and this gives them some claim to expert knowledge in particular topics, but also a high-level of general knowledge in their chosen discipline. Most employers of specialists see it this way, and in my experience it rarely matters what your particular dissertation topic was, though it may matter what topics you have published in. (Besides which, in most cases your dissertation is sufficiently abstruse that eyes glaze over when you try to explain it.)

Choosing a discipline for your PhD study is important, but it is not a huge problem if your topic turns out to be substantially different from what you want to practice later. Your program should give you a good enough knowledge of the discipline that learning a new topic becomes easier and easier, and up-skilling into a new topic area is not too onerous.


I did a PhD in biomedical engineering; after a few years that career fell apart, and I ended up moving into statistics. Currently I'm working in econometrics, which is quite a long way from any of my formal quals.

In my experience, mathematics is mathematics, and if you can handle one mathematical field you can probably adjust to another. For me the toughest part was convincing potential employers that I could make that shift.

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