Teaching a fishbowl tutorial: sink or swim?

Background:  The fishbowl method is a small group teaching technique in which a number of students engage in a discussion while observers form a circle around them. We use this method to teach medical interviewing skills, with students interviewing a simulated patient (SP) whilst being observed by their peers and a clinical tutor. However, there is little evidence to guide teachers on how best to structure a fishbowl tutorial.