Kennedy's ExComm and the Cuban missile crisis
This is documented history rather than a laboratory result. The events are well recorded. What they teach is an argument, and the entry makes it openly.
In October 1962, the world came as close to nuclear war as it ever has. American spy planes had found Soviet nuclear missiles being installed in Cuba, and President Kennedy convened a group of advisors to decide what to do. What Kennedy did with that group is the lesson. He deliberately built it to disagree. He encouraged junior people to challenge senior ones, broke the group into smaller teams to argue different options, and crucially, he sometimes left the room, because he knew that when the president is present and has hinted at a preference, people stop arguing and start agreeing. The group's first strong consensus was to bomb the missile sites, an action that, it later emerged, might well have triggered nuclear war. Five days of engineered disagreement produced a different answer, a naval blockade, which gave both sides room to step back. It worked.
The quality of a group decision depends on whether the group is allowed, and encouraged, to disagree before it converges. Kennedy's instinct was the opposite of most leaders, who signal what they want and then collect the agreement, mistaking the resulting comfort for confidence. A decision that everyone nodded along to has been rubber-stamped rather than tested. If you lead, the most valuable thing you can do is make it safe and expected for people to argue against the emerging answer, and sometimes to remove yourself so they will. A comfortable, quick consensus is often the sign of a decision nobody dared to challenge.
Source: Documented history, October 1962. Drawn from ExComm meeting recordings and transcripts.
Matthew Syed, 2019
On engineering productive disagreement, and why harmonious groups make worse decisions.
Draw your own card. It does not take long, and it rewards taking your time.