The factor that affects team productivity and creativity is the ability to conduct constructive conflict. In turn, three other factors that affect that ability, which are strong in children, and disappears when they reach adulthood and the work environment.
For a team to be creative, members must get along. This cannot be forced by management, and if it is--it doesn't work. Instead, they have to share values, act in fairness, and believe that others on the team are competent. Children are very quick to realize that a member of the team is not right for the team, or that they don't belong in that team themselves. Without much fanfare, they separate from the team. For adults, however, it's not that simple. In companies, only the human resource department or the ranking manager would have the authority to remove a member from the team, and typically they are bound by fear of discrimination or any other employment lawsuits that might result. It is not much different in volunteer organizations or clubs. As a result, teams might include members that don't get along, don't complement each other, don't include the right diversity (except demographic one, mostly focused on affirmative action), or don't trust each other. And that hurts their creativity, as without trust they cannot conduct constructive conflict.
At childhood, the concept of "saving face" is not developed or important. As a result, children wouldn't mind asking stupid questions, or suggesting stupid ideas. They don't mind being told that their ideas are stupid. They immediately move on to the next idea. They don't take it personally. In studying the Marshmallow Challenge, Tom Wujec found that one of the best performing groups is that of kindergarten students. Outperforming business school graduates, and even some groups of seasoned executives, kindergarten students experimented from the beginning, and not only after they had a well thought-out (or, as it turned out, not so well through-out) plan. You see, they didn't feel ashamed if their ideas didn't work. They tried new ideas instead. The vulnerability that allows them to experiment with new ideas (key for creativity) disappears as they grow up and go into companies. The environment in which mistakes may not be tolerated, and can have adverse financial consequences, where competition for leadership positions and pay raises are pervasive, employees don't want to try things because of the possibility of failure, and how their colleagues might exploit it.
Willingness to criticize
Finally, children don't hold back. Sometimes when I speak in front of a group of adults, I say something that doesn't make any sense, on purpose, with the confidence of someone who knows that he is talking about. Rarely does anyone stand up and call BS. Do they not realize I'm wrong? They do. They are just bound by so many social norms and fear of authority that they don't say anything. Political correctness sets in. They would rather tell each other behind my back that I don't know what I'm talking about, than to my face. Plus, and this goes back to the unwillingness to be vulnerable, they are afraid that maybe I'm right and they would be wrong, making fools out of themselves. That's something they are not willing to tolerate. So they would rather not say anything. Not to me, anyway. Try doing that to a group of children. They don't care about political correctness. They don't care about social norms. They would immediately jump up and correct me.