Nemeth … divided two hundred and sixty-five female undergraduates into teams of five. … The first set of teams got the standard brainstorming spiel, including the no-criticism rules. Other teams were told … “Most studies suggest that you should debate and criticize each other’s ideas.” The rest received no further instructions. …The brainstorming groups slightly outperformed the groups given no instructions, but teams given the debate condition were the most creative by far. On average, they generated twenty per cent more ideas. And after the teams disbanded, … brainstormers and the people given no guidelines produced an average of three additional ideas; the debaters produced seven. …

“There’s this Pollyannaish notion that the most important thing to do when working together is stay positive and get along, to not hurt anyone’s feelings. … Well, that’s just wrong.”

Did they notice that they were possibly changing the amount of offense taken and feelings hurt by criticism, when they told people what was optimal? They told people that criticism was a duty, such that they probably wouldn't take it as personally, and they found that the group was more creative. But did they measure the amount or nature of criticism given in the groups?

There are many reasons why such a rule could inhibit creativity. I wonder how important each factor is.