Shared information bias makes groups repeat what everyone already knows while critical minority insights go unheard — lowering decision quality.
One of the core assumptions of working in teams is that people who come together make better decisions than individuals deciding alone. When different expertise, perspectives, and experiences combine, we expect more accurate outcomes. In practice this doesn't always happen — and one of the main reasons is the cognitive biases that quietly sabotage group decisions.
Groups are advantageous in theory; but when members don't share what they know, or don't sufficiently consider others' views, group decisions can become even weaker than individual ones. In intense, time-pressured settings like design sprints, this risk grows further.
Three core group biases stand out here. In groupthink, members suppress critical thinking and conform to the majority to avoid conflict. In shared information bias, the group repeatedly discusses what everyone already knows, while critical information held by only a few is overlooked. With hidden profiles, all the necessary information exists in the group, but no one holds all of it alone — so unless the information is combined, the right decision never emerges.
Research shows that the information discussed most in group conversations is usually what everyone already knows. As it is repeated, it is perceived as more “correct” and “important.” By contrast, information known to only one or two people — and often contradicting the prevailing view — is either never voiced or quickly brushed aside.
As a result, the group develops high confidence even though it is actually deciding with incomplete information. This leads flawed decisions to be accepted without question.
These biases create specific behavior patterns within the group. People who think critically or bring different information can be seen as those “slowing the process down,” while those who support the majority view receive more approval. Over time the group becomes a closed structure that silences dissenting voices. An extreme outcome of this is the Abilene Paradox: the group makes a decision the majority didn't actually want, because everyone stays silent assuming the others want it.
Experimental studies show that the distribution of information directly affects decision quality. When individuals form their own views before the discussion, the likelihood that new information will be considered drops. Especially when members learn others' preferences early, their motivation to process new information declines.
There are simple but effective ways to improve group decisions: designating individuals as “experts” on specific topics encourages them to share what they know; deliberately assigning a group member to question assumptions keeps critical thinking alive; and because homogeneous groups are more prone to groupthink, members from diverse backgrounds raise decision quality.
Successful group decisions are made possible not just by well-intentioned collaboration, but by deliberately designed processes. When shared information bias goes unnoticed, groups can advance toward wrong decisions with high confidence. The right decisions are often hidden not in the most-repeated information, but in what is least voiced.
