Article Abstract
Larson, J. R., Jr., & Sargis, E. G. Elstein, A. S., Schwartz, A.  (2002).  Holding shared versus unshared information: Its impact on perceived member influence in decision-making groups.  Basic and Applied Social Psychology, 24, 145-155.

Abstract.   This study examined whether perceptions of interpersonal influence in ad hoc decision-making groups are affected by the amount of shared and unshared information target members hold relative to others in the group.  Thirty-four 3-person groups performed a drug choice task.  Prior to discussion, all members individually studied a subset of the available drug information.  In one condition, a randomly selected target member was given more shared and less unshared information to study than others in the group.  In a second condition, the target was given less shared and more unshared information than others.  All groups then discussed the drugs for up to 25 minutes and decided which one would be best for a particular application.  It was found that targets who initially held more unshared information than others were perceived to have had more influence than targets who initially held more shared information, and this effect was mediated by the targets' discussion behavior.  These results are interpreted in terms of the greater potential impact that unshared information can have during decision-making discussions, and the transfer of that impact to members who hold more unshared information than others.