The common-knowledge effect is a decision-making bias in which teams focus on information that is known by all members and overlook unique knowledge held by individuals. Psychologists have found that teams often engage in poor decision making because they spend too much time discussing commonly held information. In a scenario where teams are given unequal access to project statements, it has been observed that teams are less effective at selecting the optimal project compared to individuals. Factors such as information availability and memory, preference bias, and social comparison contribute to the common-knowledge effect. This phenomenon is particularly relevant to UX professionals who often make team decisions and may face information asymmetry and being outnumbered. Mitigating the common-knowledge effect requires promoting psychological safety, being aware of role-power imbalance, considering virtual teams, disregarding past opinions, prioritizing data gathering, visualizing the data, involving others in UX research, and being cautious of using a devil’s advocate. Overall, it is important to ensure that all team members share their unique knowledge to avoid the common-knowledge effect and make optimal decisions.
https://www.nngroup.com/articles/common-knowledge-effect/