Imagine for a moment what will happen when one member of a team is having difficulty with some assignment, say celestial mechanics. Everyone else on the team will bring all their resources to bear to assist the person having the problem. They will go to great lengths to help each other because they know none of them will get to go unless they all do. This method creates powerful incentives to work together in a cooperative, mutually supportive, and effective manner. Crew performance depends upon many things, but one is communication.
Communication depends on trust.
We only speak honestly to those we trust. To others we present that which we believe will be seen as acceptable. Trust has to develop out of experience with risk taking. Risks are only taken where mistakes are not punished. Accordingly, enhancing crew performance requires a process whereby the selection of the crew enables people to take risks to optimize learning without feeling that mistakes made jeopardize their chance to go on a mission.