This is one topic that I thought could have used a little more attention in “Getting What You Came For” (review pending), given that it’s the one decision that has the largest impact on graduate school success. So, here are my thoughts.
First, a caveat. My experience is with the Canadian system, where a student approaches potential supervisors before formal application to the university. For the first few years classwork and research go hand in hand, and except for a few edge cases a student will always be working in the lab .
This system requires that the student decides their field of research while still an undergraduate, without a lot of the expertise required to rank potential supervisors. It’s always best if your professor is a leader in his field, but would you learn more with the up and coming assistant professor at Prestigious U? Should you pick your professor like a 90’s President, or is it better to have a hands-off relationship? Which factors matter, and which don’t?
Looking back on my experience , the three most important factors are the age of the professor, the frequency of publications and the size of the lab. Within reason the prestige of the university is a secondary concern at the graduate level, provided there’s enough funding for equipment.
Age of the Professor
In general, the output of a professor will decrease over time, as they rise from assistant to associate (ie. tenured) to full professor. This is partly due to increasing age, and partly because senior faculty often serve on many committees that take up the bulk of their time . This trend can be somewhat offset by success, as a good publication record will lead to larger grants mid-career.
However, working under a young assistant professor carries significant risk. The most worrisome is simply that they will not get tenure, and will be forced to leave the university. When a professor leaves most of his students will need to leave as well, finishing their studies wherever their supervisor lands. If the PI leaves academia entirely, the students will need to find alternate labs willing to take them, regardless of the research.
That’s a dark picture of course, but tenure rates appear to be around 54% in the US (cite, pdf). Rates are higher in Canada and in smaller universities (cite, pdf), but beware. The first few years of a professor’s time in a small university are generally given over to setting up the lab, building equipment, and applying for grants. Working in this environment will give you an excellent education, but the lab is unlikely to produce as many publications as it would five years later on . Unfortunately, building skills is secondary to demonstrating them, and publications are the most important thing for a young researcher.
To synthesize, the best time to join the lab is 5-10 years into the professor’s career. Look for labs where the PI has either just received tenure, or is sure to do so within the next twelve months.
Frequency of Publications
This is a simple matter. Using the Web of Knowledge/Scifinder/PubMed look up how many papers the prospective PI has published in the last five years. A good minimum is one paper per year, per student (larger labs will publish more in total, but may be less efficient). Year-to-year consistency is important, as it reduces the impact of one or two star students .
Size of the Lab
This may be a little contentious, but I think that on average it’s better to do your PhD in smaller, less prestigious labs. The more students a supervisor has the more his attention is divided, and the less mentoring you will receive. This can be partly counteracted by support from your fellow graduate students and the lab’s postdocs/research associates, but leaves a lot of your success up to chance. In the worst case the lab will be so large that the professor can maintain his grants on the few golden boys/girls that produce high value research, consigning those who don’t perform to a long, isolating PhD .
At the other end of the spectrum we have the 1-5 person lab, where a single bad student or postdoc can sink the professor’s tenure application or next grant. Students in these labs will have daily or semi-weekly meetings with their PI, and quick responses to any draft publications or theses. But, the lab is small enough that students may often run into problems that neither they nor their supervisor can solve. The best balance is therefore the small to medium sized lab (4-12 people), where every member of the lab can approach the professor as needed, but there is enough collected expertise in the students/postdocs/etc. to tackle most problems.
Peters mentions some good secondary characteristics, like the distribution of credit between professor and student (ie. first authorship) and the length of the average PhD, which I would use to distinguish between several similar candidates. A good working relationship with the professor is essential, but it isn’t necessary for you to be best friends. Always speak with the students and the PI before formally applying to the university, even if you can only chat on skype.
In summary, the best lab for a budding graduate student:
- Has a PI who has either received tenure in the last ten years, or will receive tenure in the next twelve months.
- Reliably publishes at least one publication per student per year, reviews and ancillary publications included.
- Has between seven and twelve students, postdocs and research associates.
 This contrasts with the American system, where students apply to the department and only begin research after surviving their qualifying exams. In such a system it’s best to go to a university where there are several potential professors you could work under, to account for funding trouble and other externalities.
 All standard disclaimers apply. Your mileage may vary, I am not you, things were different back in the day, etc.
 For this reason, in most cases it’s a bad idea to work for the department head. He’s prestigious and can write excellent letters of reference, but nine times out of ten will not have enough time to properly mentor you. The exception to this rule is if the lab has a strong, permanent research associate or other authority figure who can act as a surrogate mentor.
 If you are an undergrad and get the chance to help set up a lab, take it. You’ll learn a lot and likely receive an excellent letter of reference.
 Web of Knowledge has a nice “journal citation report” function. Search by name and address (ex. Findlay B/Manitoba) and click on the button on the right hand side of the publication list to see H-index, publications per year and citations per year.
 This is another case where it’s all about where you are in your career. Larger labs can be great for postdocs, in part due to the prestige of the larger lab and in part because the postdocs don’t require the same level of attention from their PI. In a large lab the postdocs can act as a problem solver, mentoring several graduate students and mastering the chemistry required for several different projects at once. I can think of little better training for an assistant professorship.