Exercise idea: provide a list of questions that have objectively right answers such as how many bones are there in the human body. Have each person on his own guess at the answers. Next, put everyone in a small group and have the groups discuss the questions and then have everyone individually redo their estimates. Finally, combined each small group with one or two others and repeat what was done before.

Tell everyone at the start of the exercise that their goal is not to just get the right answers but to also identify causes of persistent disagreements within their decision group.

I did this once in my game theory class and the students loved it, although I didn't measure how much they learned from the exercise.