Shared Information Bias

The glitch, explained plainly.

Imagine your family is trying to pick a restaurant. Everyone keeps talking about the pizza place they've all been to, because it's easy to agree on. But your little brother went to an amazing new taco place last week that nobody else has tried. He tries to mention it, but everyone keeps going back to talking about the pizza place because that's what they all know. So you end up at the pizza place again, even though the taco place might have been better.

When groups convene to make decisions, they systematically over-discuss information that all members already possess while under-discussing unique insights held by individual members. This creates a paradox: the very reason groups are assembled—to pool diverse knowledge—is undermined by a collective gravitational pull toward the familiar and already-known. The bias is amplified when groups face time pressure, seek consensus, or work on ambiguous judgment tasks rather than problems with demonstrably correct answers. As a result, groups often arrive at inferior decisions that any single well-informed member could have improved upon, because critical unshared information never surfaces or is dismissed when it does.

Where it shows up.

1. 01 A hospital diagnostic team meets to discuss a patient with puzzling symptoms. The three doctors spend 40 minutes debating the lab results they all reviewed, while the nurse who noticed an unusual medication interaction in the patient's history tries twice to bring it up but is talked over. The team settles on a diagnosis consistent with the shared lab data, missing the correct diagnosis that the nurse's unique observation would have revealed.
2. 02 A startup's leadership team gathers to choose between three potential office locations. Each executive visited all three sites, but each also gathered unique local intelligence—one learned about upcoming construction, another about a tax incentive, a third about transit changes. The meeting is dominated by debate over rent prices and square footage that everyone already knows, and the team picks a location without ever surfacing the construction disruption that would have changed their decision.
3. 03 A hiring committee reviews five candidates. Each committee member interviewed different candidates in addition to two they all interviewed. During deliberation, 80% of the discussion centers on the two commonly interviewed candidates, with rich anecdotes and comparisons. The uniquely interviewed candidates receive only brief, surface-level mentions, and the committee selects from the commonly seen pool despite one uniquely interviewed candidate being objectively stronger.
4. 04 A product team at a tech company holds a retrospective after a failed launch. The engineers, designers, and marketers each have distinct insights about what went wrong in their domains, but the meeting keeps circling back to the server outage everyone witnessed. The design flaws and market misread that individual members uniquely understood are barely mentioned, so the team's action plan addresses only the infrastructure issue.
5. 05 A jury deliberates on a fraud case. Eleven jurors fixate on the defendant's suspicious financial records that were central to the prosecution's closing argument—evidence everyone remembers clearly. One juror, who paid close attention to a brief expert testimony about industry-standard accounting practices, tries to contextualize the records but is dismissed because no one else recalls that testimony. The jury convicts based on the collectively salient evidence alone.

Where it shows up at work.

The same glitch looks different depending on the terrain. Finance, medicine, a relationship, a team — same mechanism, different costume.

In history.

• The Bay of Pigs invasion (1961) is frequently cited as an example where Kennedy's advisory group discussed widely shared assumptions about the plan's viability while failing to surface and integrate unique dissenting intelligence held by individual members.
• The Columbia Space Shuttle disaster (2003) investigation revealed that critical engineering concerns held by lower-level NASA engineers were not effectively surfaced in group decision-making sessions dominated by commonly held managerial assumptions about foam strike risks.