Limitations of supervisory expertise
How far should I, as a PhD supervisor*, allow my students' work to stray outside my own area of expertise?
Since research necessarily involves venturing into the unknown, it is not at all uncommon, particularly in exploratory rather than goal-driven research, for the next stages of students' work to require expertise outside that of their supervisors.
Where only a relatively small amount of reading or consultation with other academics is required, supervisors may be happy to let students get on with it, provided that they are kept informed, and to learn from or with the students. Where the new expertise is considerable, however, a common solution is to bring in additional supervisor.
Dangers of allowing a student's research to stray outside the expertise of the supervisor
Bringing in an additional supervisor, particularly well into a student's work, can have more than its fair share of problems. Neither supervisor is an expert in the other's field and students can all too easily find themselves pulled between conflicting advice.
It must be stressed that problems with additional supervisors do not necessarily apply to backup supervision, where the main supervisor retains the overall responsibility while backup supervisors provide support while the main supervisor is temporarily absent. Neither do the problems apply where an experienced supervisor oversees the main supervisor while he or she is new to the job. Neither do they apply to panel or committee supervision where the roles and responsibilities of each supervisory member are negotiated and agreed at the outset of the programme of work and then reconsidered at defined points, ideally through a chairperson.
The way forward
Clearly a balance needs to be struck between constraining the research to stay within the expertise of the main supervisor and allowing full rein to a student's enthusiasm, originality and independence. There is a lot to be said for this balance being as far towards the former as seems reasonable. Students need a supervisor they can trust to advise, warn and encourage them. Generally they agree, once they understand the reasons.
edited extract from no 2 in the Guides series
Resolving Common Dilemmas in Supervision
by Pat Cryer