In 1958 Yale measured what a meeting costs you

Alex Osborn, a New York adman, published Applied Imagination in 1953 and left behind a promise that is still repeated in every office: a group saying ideas out loud without criticising each other produces far more than its members would separately. Five years later, three psychologists at Yale measured it and got the opposite result. Donald Taylor, Paul Berry and Clifford Block put students into groups of four and gave them open-ended problems, including a famous one: what would happen if everyone were born with an extra thumb on each hand.

Then they set up the honest comparison. They took other students, let them think on their own, and pooled their lists afterwards, throwing out the duplicates. Those paper groups won: more ideas in total, and more distinct ideas, than the real groups of the same size.

In 1987, Michael Diehl and Wolfgang Stroebe, at the University of Tübingen, found the main reason and gave it a name: production blocking. While one person talks, the other three cannot, and in that gap they forget what they were going to say, or decide it is no longer worth saying.

Try it at your next meeting: hand out paper and five minutes alone before anyone speaks, collect the lists, and only then start arguing.