What incentives does an advisor have to help PhD students graduate in a timely manner?

Question

I've heard it suggested several times on this site that advisors (especially in experimental fields where the PI may benefit from a cheap, highly skilled workforce) have an incentive to prevent their PhD students from graduating in a timely manner, or at least that they have no incentive to actively promote graduation when the student is "ready." (Whatever "ready" means for that particular student.)

For example, user47148 says

You are the only one who cares if you finish. To your advisor you are cheap labor.

bfoste01 says

I often wonder if keeping highly-skilled cheap labor around to do something with the data that a PI is collecting from a high-profile grant is often an implicit factor that impacts students' trajectories. In which case it is not uncommon to see students in their 6th or 7th year of the program receive funding.

and grandmah77 refers to

keeping your advisor from keeping you there forever as cheap labor.

I am interested in learning more about the opposite: what incentives do advisors have to help their students graduate as soon as they're ready?

This question discusses incentives for advisors to increase their PhD completion rate. Presumably this is part of the answer, because a student who isn't allowed to graduate in a timely manner might just drop out instead.

But besides for that, what incentives (if any) does an advisor have to help students graduate when they are ready, rather than dragging out the length of their degree?

(In some programs, there are policies that limit the duration of PhD funding. I'm asking about programs where PhD students can potentially hang on for several years past the mean time-to-degree.)

P.S. answers supported by references to actual data would be amazing.

Answer 1

This is very simple. I care about my students, and want the best for them. Languishing in graduate school is rarely optimal for anyone. And then there is the issue of funding. For the same reason -- concern for my students' wellbeing -- it is very important to me to provide them with RA funding as close to year-around as possible. If funding starts to get tight, it doesn't help to have someone taking a luxury sixth year when he or she could have graduated earlier. I'd rather have everyone funded on RAships than have so-called "cheap labor" from senior students while junior students are forced to TA.

If the question is referring to why even a sociopathic advisor would want his or her students to graduate on time, there is some prestige in having students graduate quickly and move on to good positions, and some shame in having students in their sixth, seventh, and later years.

Answer 2

The incentives vary strongly by location, although I think the usual driver is monetary. For instance, in Germany, it is difficult to be employed as a PhD student at a single university for more than six years (following the completion of the master's degree). Moreover, because the recruiting of PhD students is often done "from within," if a professor becomes known for not graduating students, it can hurt long-term recruiting. (Also, DFG funding typically can be extended on a single project for five years.)

For US professors, there may be an expectation of graduating a certain number of students as part of the requirements for being granted tenure. However, I think the bigger incentive is that beyond a certain point it becomes too difficult to keep finding funding for a long-term student.

Answer 3

At least at the university i'm at in the UK (and I belive this is true in the UK more generally and is pushed on them but some national body though i'm not sure offhand which) there is a 4 year limit on regular full time PhDs that can only be extended in exceptional circumstances. Students who fall off the end of said limit reflect badly on the department. Things that reflect badly on the department tend to result in the head of department having a go at the indidvidual academics who caused it

I belive this came about precisely because so many PhDs were dragging on for years and it was considered desirable to put pressure on both students and academics to finish up the PhD and move on.

Answer 4

Pride, and the sentiment of a job well done.

Sure, as a supervisor, one is the student's "boss", in some places in the world, it's even formally the case (where PhD students are employees). But the adviser-student relationship is also the one of an experienced academic guiding a promising student on the path to become independent and start contributing to the field.

Getting the PhD degree is a milestone on that path, it's the point where an adviser feels confident that the student is mature and that the work enclosed in the thesis will be looked as worthy of the degree by everyone in the field. Some people are perfectionists and think as long as there is funding, there's an opportunity to make the work even stronger, but other than that, who would want to delay that sentiment?

Answer 5

Good students reflect well on their advisers, but only when they're out in the world producing results on their own.

When I first arrived in my department, I was told, "We very much want you to succeed and do great things, and in return we'll bask in the reflected glory of your accomplishments and get credit for raising you." And indeed, everyone is expected to complete the masters + PhD program in 5 years in my department.¹ (It used to be 4 not so long ago!) Though I'm not a professor myself, I can imagine there is a great deal of respect to be had in the community for training excellent researchers.

Moreover, the arithmetic is simple: if you keep your grad students longer, a fixed total amount of funding (and personal time) will cover fewer of them. Consider that in the limit of pure grant money with no university teaching support, keeping grad students around 7 years instead of 5 means you will be able to take on 30% fewer total students. I suppose this doesn't apply to professors who force students to fund themselves and who don't spend any actual time training those students.

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Also, basic decency should be mentioned, obvious though it may be. Professors don't have to be coldhearted, amoral, selfish, rational agents bent on amassing large amounts of slave labor.

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_{¹Yes, this is a department policy. It's also a university policy, but other departments flagrantly violate it. Moreover, I've never heard of any similar policy in my field (we're rather infamous for kicking students out fast). So the fact that all my professors impose this on themselves means they must have internal motivations.}

Answer 6

Prospective Ph.D. students talk to each other. Smart applicants will notice that a potential supervisor's students take a long time to finish, and they will go elsewhere. Professors looking for good Ph.D. students need to be attractive to candidates, too, so they have an incentive to do their best by them: supervise and coach them well, help them in their careers (also post-Ph.D.), integrate them in their network, connect them to other relevant people... and get them to graduate soon.

And if you have a good Ph.D. student, he will do his best to get the job done, write publications and graduate. I assume most professors would rather have two smart and driven students that do their Ph.D.s in three years back-to-back, than a single laid back student that takes six years and ends up with half as many publications as the two good students had after six years.

Finally, the most important driver will likely be that your money runs out. In Germany, grants are typically for three years, and you are expected to have finished both the study and the Ph.D. student's Ph.D. by that time. If you need more money, it will be progressively harder to get. Funding agencies notice whether you get your results in three years, too.

EDIT: a longer list of Ph.D. students also looks nicer on a professor's CV. Better to have supervised two students in a six-year time span than only one. This is also sometimes incentivized by universities, in the form of a modest cash bonus per graduated Ph.D. student, or per Ph.D. student that graduated without taking longer than x years.

Answer 7

Mostly because it is very difficult to get the funding to extend the duration of the PhD position significantly. This is a very strong "motivation" for both student and professor, and there is no need for another one.

Failure to produce the descent PhD thesis during the allocated time would harm the reputation of both.

As a result, a professor usually cares about the success of the PhD studies. If the student is really bad, he is normally discarded as early as possible, way before the end of the PhD duration. Similarly, if there are some problems with professor, laboratory or research topic (also happens), a PhD student normally tries to migrate to another laboratory and this is relatively easy to do.