PhD supervisory committees
The responsibility of the PhD supervisory committee, according to FoGS, is "to provide constructive criticism and assessment of the student's ideas as the program develops, thereby broadening and deepening the range of expertise and experience of the graduate student", as well as "to be available for help at every stage of the student’s program, from selection of coursework to formulation of the research proposal ... to presentation and publication of the dissertation or thesis". Moreover, the added perspective of committee members can be crucial for pointing out, to supervisors, ways in which a student's plans or progress might be addressed or improved (and also by staying cognizant of upcoming degree requirements and deadlines). Finally, the supervisory committee can also provide support in cases where the relationship between student and supervisor is not working well or is even in danger of becoming dysfunctional.
It is fair to say that when everything is going well, the supervisory committee is somewhat redundant, especially given our department's culture of being open to mathematical and career-related discussions with one another's students. However, a small but present minority of PhD students have trouble establishing contact with faculty members other than their supervisor; a small minority of PhD students encounter obstacles to progressing through the program that set them significantly behind schedule; a small minority experience problems in their relationship with their supervisor. The continued involvement of the PhD supervisory committee is an insurance policy, with extremely modest cost, towards rectifying any complications that arise and keeping students steadily upon their paths forward. In this sense, the committee is like any graduate policy or degree requirement: it is most beneficial to those who need it most, and we can't always predict in advance who will end up needing it most.
FoGS directs PhD students and their supervisory committees that meeting twice a year is ideal. The best time for such meetings is every April and October, timed to take place before the biannual graduate tracking surveys are filled out. In this way, the PhD student can update all the members of the committee on their progress over the previous six months, and the committee can give their input to the supervisor and student regarding planned activities for the next six months. Alternatively, a student can update each member of the committee separately, and then the committee can meet amongst themselves (although there is no need for the student to feel pressure in talking to a panel of volunteer mentors!). Of course, interactions among these parties are likely to happen all year long; these meetings can be times to gather and examine the student's achievement in its totality.