Article Abstract
Winquist, J. R., & Larson, J. R., Jr. (1998).  Information pooling: When it impacts group decision making.  Journal of Personality and Social Psychology, 74, 371-377.

Abstract.  Three-person groups decided which of 2 professors was the one nominated for a teaching award.  Prior to discussion, half of the information available for this decision was given to every group member (shared information), whereas the rest was evenly divided among them (unshared information).  Further, this information was distributed in such a way that the correct choice was not obvious to members prior to discussion.  As predicted, discussion focused more on members' shared than unshared information.  However, decision quality was affected only by the amount of unshared information discussed, and by member's pre-discussion choice preferences.  The amount of shared information discussed did not affect decision quality.  These results suggest a dual-process model of how the pre-discussion distribution of decision-relevant information impacts group decision making effectiveness.