This gets strange looks in the first class session, but people catch on and it starts to feel less like group therapy. This grounding is important. Each time, the circle and the notion of listening respectfully to each other are reintroduced experientially. Once listening is established in the room, it remains. Using the circle allows each person's voice to occupy the room, establishing a kind of territory.
Participants find it easier to speak when others listen respectfully.
I do vary the format, sometimes giving a mini-lecture when there is a problem with material or a particularly complex setting. I sometimes jump to the board to record in tangible form a particularly productive or interesting line of discussion as it goes around. There are several direct effects. Participants pay attention. Thoughts are carefully marshaled.