Shared Information Bias
Groups discussing what everyone knows, not what one member knows
What is it?
Shared information bias is the tendency of groups to spend their discussion on facts that every member already knows, while facts held by only one or two people rarely come up. Garold Stasser and William Titus showed it with the "hidden profile" design: when the information that pointed to the best candidate was spread across members, groups often failed to pool it and settled on a worse choice. Shared facts are mentioned more often, repeated more easily and confirmed by others, so they feel more valid, while a unique fact has one voice and no echo. This differs from groupthink: the group need not be under pressure to agree; the problem is how information circulates. It bites in hiring panels, medical teams, investment committees and family decisions where each person holds a different piece. It tends to get worse when members arrive with a preference already formed, when discussion is short, and when the person holding the unique fact is junior or new.
Example
A hiring panel spending the meeting on the CV everyone read, while the one interviewer who checked references never mentions what they heard. A project team repeating familiar metrics while the engineer's warning about a supplier stays unspoken. Siblings choosing care for a parent without pooling what each one has noticed on visits.
References
Stasser, G., & Titus, W. (1985). Pooling of Unshared Information in Group Decision Making: Biased Information Sampling During Discussion. Journal of Personality and Social Psychology, 48(6), 1467-1478.
Lu, L., Yuan, Y. C., & McLeod, P. L. (2012). Twenty-Five Years of Hidden Profiles in Group Decision Making: A Meta-Analysis. Personality and Social Psychology Review, 16(1), 54-75.
How to Prevent It
Doxa uses AI and can make mistakes. How it's built
What do I know about this that no one else in the room knows?
Are we spending our time on points everyone already agrees on?
Who here had access to information the rest of us did not?
Has the quietest or newest member told us what they know?
Would our choice change if one overlooked fact were taken seriously?
Ask each member to list, before the meeting, facts they think only they hold.
Share all the relevant information in writing before anyone states a preference.
Give each member a distinct area to report on so unique facts have an owner.
Frame the meeting as solving a problem, not as voting on options.
Keep a visible list of new facts raised and check it before deciding.