The first voice sets the frame
Group discussion has a structural property that undermines its main purpose, and understanding it explains most facilitation technique.
When a question is opened to a room, the first substantive contribution does disproportionate work. It establishes what kind of answer is expected, which considerations are relevant, and what the range of acceptable positions looks like. Everyone who speaks afterwards is responding to it, whether they agree or not.
That is anchoring, and it is one of the most robust findings in judgement research, going back to Tversky and Kahneman in 1974. Numerical estimates shift toward whatever number was mentioned first, even when the number is obviously arbitrary, and knowing about the effect does not remove it.
In a meeting the anchor is not usually a number. It is a framing, and it is set by whoever speaks first, which is systematically the most senior, most confident, or most extroverted person present rather than the most informed.
The compounding problem. Once two or three people have expressed a view, the cost of disagreeing rises. Solomon Asch's conformity experiments in the 1950s showed people denying the evidence of their own eyes on a trivial perceptual task when a unanimous group said otherwise. Real meetings involve ambiguous questions and colleagues you will see tomorrow, where the pressure is considerably stronger.
So a discussion does not aggregate independent views. It aggregates one view and a series of responses to it, which is a much weaker instrument.
Which yields the single most useful principle in facilitation. If you want a group's independent judgement, you must collect it before people hear each other. Everything in the next step follows from that.

