Social science research shows that people are reluctant to say information which is unique to them. That is, if they are the only person who knows something, they will often not say it even if it is very important to the group’s decision. This tendency should be countered if possible.

Possible causes of the phenomenon

Ideas for fighting UniqueInformationSharing

The Quakers, if I recall correctly, have a tradition of requiring that everybody say something, after a period of meditation. Not practical for anything but small groups, and sometimes you have to call a time-out on people who talk too long, but it works. Part of the motivation is just this problem. – LionKimbro