How the bias narrows what the group remembers
Collective memory—what a group can recall together—depends on information being surfaced and acknowledged. In a collective memory task, groups tend to rely on recall of shared information because recall of unshared information is by nature more fragile: only some members hold it, so it needs to be voiced and picked up by others to enter the group's memory [3].
Studies of collaborative recall show that differences in how shared and unshared information are acknowledged affect what the group ultimately remembers [4]. When unshared details are less discussed, they are less likely to be repeated, rehearsed, or integrated, so the group's pooled memory ends up closer to the common ground than to the full distribution of knowledge across members [3][4].
What this means for teams trying to remember together
The practical implication is that a team's collective memory can be systematically narrower than its members' combined knowledge. Because shared information is discussed more and evaluated more positively [1][2], unique details held by one person risk being dropped unless someone deliberately brings them in and the group acknowledges them [3][4].
Knowing how access to information is distributed among members can help: when groups are aware of who knows what, they may be better positioned to pool unshared information rather than defaulting to what everyone already shares [3]. The evidence points to a bias in discussion and recall, not an inevitable limit—but without deliberate effort, the group's memory tends to reflect the shared core rather than the full picture [1][3].
Sources used in this answer
Discussion of shared and unshared information in decision-making groups.
Decision-making groups discuss much more of their shared information than their unshared information.
The collective preference for shared information
Group members collectively evaluate shared information more positively than unshared information, contributing to a preference for discussing shared information.
Pooling unshared information: The benefits of knowing how access to information is distributed among group members
In a collective memory task, groups tend to rely on recall of shared information because recall of unshared information is inherently more demanding.
The effect of information distribution on collaborative inhibition
Differences in how shared and unshared information are acknowledged affect collaborative recall and collaborative inhibition in group memory.
From cooperative to motivated information sharing in groups: Moving beyond the hidden profile paradigm
A review of the literature frames groups' favoritism toward shared information as motivated information sharing rather than purely cooperative sharing.