Biases in Collective Decision-Making – Part 2


Some time ago we discussed about the bias in sharing information within a group. This previous article was the first in a series of three. Today, we will talk about a second bias. Without too much suspense, this bias is called: groupthink.

Read also on our blog

Biases in Collective Decision-Making – Part 1

What is it?

At first, groupthink, does not appear problematic. Yet this is a phenomenon that often appears in very cohesive groups.

Between 1972 and 1983, Irving Janis (1) has worked on this phenomenon and proposes the following definition: “A desire for cohesion within a group that produces pressure to uniformity, self-censorship and unanimity.” In other words, groupthink eliminates critical thinking and the research for alternative arguments to first decisions.

In 1961, the Bay of Pigs Invasion is an example of groupthink. The decision to land 1,400 trained anti-Castro Cuban exiles to overthrow Fidel Castro’s government, was made by a team of experts. Their strong cohesion produced groupthink and led to a bad decision, since the landing was a bitter failure due to several false assumptions which could have been foreseen by a careful evaluation process.

Members of the group are blinded by the cohesive power that prevails and do not take into account the risks involved in the decision.

Irving Janis identified four stages that characterize groupthink.

1. Antecedents -A time pressure
-An authoritarian leadership
-A Strong cohesion
2. Symptoms-An illusion of unanimity
-A conviction of the merits of the collective decision
-A rejection of opponents.
3. Processing defective information-Little research of new information,
-An incomplete sharing of information,
-A lack of consideration of possible alternatives,
-A failure to reconsider the decision reached.
4. The result-A faulty decision-making.

These contexts inhibit the ability of the group to use cognitive resources of its members and urge them to find a rapid solution that satisfies everyone. However, the decision made is seldom the best, and often the worst.

A few recommendations:

In 1982, Irving Janis (2), produced a list of 10 recommendations to avoid groupthink.

  • Talk to group members about groupthink, its causes and consequences.
  • Recommend to the moderator of the meeting impartiality so that all positions can be expressed.
  • Proposing the role of “devil’s advocate”
  • Introduce sequences in subgroups, then in plenary meetings, show the differences in their conclusions.
  • Before endorsing a decision, hold a “second chance” meeting where everyone is asked to express any doubts.
  • Invite an outside expert on a regular basis to challenge group’s ideas.

Each of these recommendations can be implemented independently of one another. The important thing in a group is, on the one hand, to keep in mind that groupthink exists and, on the other hand, to try to be open to any other external proposition. 


Obviously, it is not easy to take a step back and to realize phenomena that take place within the group. The priority is to have the knowledge of the problems that can arise and to send a warning when you get the impression that decisions are made too quickly, or too easily.

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References :

(1) :  Janis, L.L. (1972, 1982a). Victims of groupthink. Boston : Houghton Mifflin.

(2) :  Janis, L. L. (1982b). Counteracting the adverse effects of concurrence seeking in policy planning groups : theories and research perspectives. In H. Brandsätter. J.H. Davis et G. Stocker Kreichgauer (Eds.), Group decision-making (pp. 477-501). New York : Academic Press.

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