Teams perform worse when newcomers hold critical information than when original group members do

In this study, two new acquaintances joined an online chatroom, spent five minutes discussing the qualities of a job candidate, then a newcomer joined the chat. The three group members (N_triads = 370; N_participants = 1110) engaged in the Hidden Profile Task during which they chose the best job candidate among four to hire. Before they began, all group members received common information and one group member-either one of the initial members or the newcomer-received critical, unshared information about one candidate that the team needed to make the correct decision. Teams in which the newcomer held critical information were less likely to make the correct decision than teams in which one of the initial members held it. Newcomers with critical information showed weaker linguistic coordination to group members-a measure of social alignment that captures the degree to which group members mimic each other's language style-and reported greater perceived task conflict than newcomers who did not have critical information. Lastly, we tested whether a manipulation of prestige-based status-giving false feedback on a test for skills ostensibly relevant to decision making-could overpower newcomer status; however, we did not find credible evidence that it did so. These findings illustrate the power of brief interactions for shaping biases against newcomers.