How the ‘common knowledge effect’ can undermine team decision-making

You’ve probably seen this happen: A team gets together to make a decision on how to move forward with a new product, a new process, or a new policy. Everybody quickly agrees on steps to take.

And then, weeks or months later, it becomes clear that this team — full of smart people, led by an effective leader — blew it. The product, process or policy doesn’t work. What went wrong?

Think about it this way: When you call on your team for a decision, you want to get a diversity of input – you want team members to share their collective knowledge, ideas and experience. But studies show that there’s something about group discussions that makes it less likely team members will do that. Paradoxically, a process that’s supposed to uncover knowledge can actually shut it down.

Suppressing facts

One reason for this paradox: Something that researchers call the “common knowledge effect,” which acts on discussions to suppress facts – often the very facts that the group should be considering as it arrives at a decision.

The common knowledge effect leads to groups mostly rehashing shared knowledge – information that everyone knows already. Important information that only one or two group members possess is either ignored or never gets put on the table at all.

A study detailed in the Harvard Business Review shows the common knowledge effect in action.

Puzzle pieces

Researchers asked doctors to view a patient video and then come together to decide on an appropriate diagnosis and treatment. But different doctors saw slightly different versions of the video, none of which told the whole story. So each doctor had a piece of the puzzle, but none had the complete picture.

If the doctors had shared all of their knowledge from the videos during the group discussions, the decision would have been obvious. Instead, they discussed only the information that was in every video – the common knowledge. And those who had uncommon knowledge – knowledge that would have led to the correct diagnosis – didn’t share it with the group. So the teams made the wrong decisions over and over.

The “common knowledge effect” has been replicated in multiple studies and a variety of settings. In each instance, groups made bad decisions based on incomplete knowledge.

Early consensus

So, why does the common knowledge effect happen? And how can it be prevented?

The main driver is the desire for an early consensus – which often causes teams to fast-forward through the crucial fact-finding phase. When people come together to solve a problem, there’s enormous pressure to quickly agree on a set of facts so they can get to the “real work”:  coming up with a solution.

Bringing up contradictory information seems counterproductive: It disrupts this early consensus and often sends the group back to square one. So the keepers of this information stay quiet. Or if they do bring up contrary facts, they back down when the group dismisses them.

Information, reputation

Psychologists say that group members censor themselves because of two kinds of pressure: informational pressure and reputational pressure.

Informational pressures cause people to defer to information that’s already been expressed by other members of the group. When a particular version of facts gets an early consensus, it tends to be accepted as the “true” version. Contradictory information is seen as less reliable – even to the person who possesses it.

Reputational pressures cause people to keep quiet because they fear losing status if they speak up. While some enjoy being a contrarian, most don’t want to seem argumentative, disagreeable, out of touch or wrong.

What to do

So how can you, as a manager, overcome the common knowledge effect?

Here are some recommendations, based on the research:

• Frame the initial discussion as a “fact finding” mission. Communicate that the goal of this first meeting is simply to bring all relevant information out in the open. Save problem-solving for a follow-up meeting.
• Ask people to submit relevant facts in advance. That way, all factors that could inform the team’s decision are out on the table before people are subjected to the group’s influence.
• Disrupt early consensus. If the group gravitates early on toward a certain set of facts, challenge the process. Solicit additional information and opinions. Ask, “What facts have we not considered here?”
• Designate a devil’s advocate, a team member to serve as the contrarian who will actively challenge the consensus and probe for additional knowledge. A member who is openly assigned to this role will feel less social pressure to conform and will be more likely to raise red flags.

This blog entry is adapted from the Rapid Learning module “For the good of the group: The secret power of social norms.” If you’re a Rapid Learning customer, you can watch the video here. If you’re not, but would like to see this video (or any of our other programs), request a demo and we’ll get you access.

The blog post and Rapid Learning video module are based on the following research article: Blanton, H., et al. (2001). “An Introduction to Deviance-Regulation Theory: The Effect of Behavioral Norms on Message Framing.” Personal and Social Psychology Bulletin, 27(7), 848-858.

Team dynamics: Group decision making – The early consensus trap

Sunstein, C. R. and Hastie, R. (2014). Making dumb groups smarter. Harvard Business Review, 92(11), 90-98.