This research reveals the factors important in designing a group support environment by focusing on a distributed cognitive environment where group members have different information. We find that closeness within a group enhances group performance when group members use a tabletop CSCW environment. To confirm this, we conduct experiments that observe human behavior in a distributed cognitive environment. Participants play a maze game in which players with restricted and distributed information communicate with each other to catch a rapidly moving target. Group performance in two CSCW environments was compared: a normal LCD setup that prevented indirect communication and a tabletop display, Lumisight Table. Group performance was found to be higher with the tabletop display, and the performance advantage was reinforced by the closeness of the group members.