Article Abstract
Larson, J. R., Jr., Foster-Fishman, P. G., & Franz, T. M. (1998).  Leadership style and the discussion of shared and unshared information in decision-making groups.  Personality and Social Psychology Bulletin, 24, 482-495.

Abstract.   This study found that during group decision-making discussions, shared information (i.e., information held by all group members) was brought into discussion earlier, and was more likely to be mentioned overall, than was unshared information (i.e., unique information held by just one member or another).  These results are consistent with a dynamic information sampling model of group discussion.  It was also found that groups with a participative leader discussed more information (both shared and unshared) than groups with a directive leader, but that directive leaders were more likely to repeat information (especially unshared) than participative leaders.  Finally, it was found that leadership style and the information held by the leader prior to discussion interacted to influence group decision quality.  The relevance of these findings for existing contingency theories of leadership is discussed.