Everyone knows the concept of groupthink. A tightly knit and overconfident set of decision makers form an insular echo chamber, fail to see the big picture, and end up making disastrous decisions.

By now, most of us think we have a good sense of the sorts of conditions that cause groups to fall into this trap. But how good is that understanding?

Let’s...

Everyone knows the concept of groupthink. A tightly knit and overconfident set of decision makers form an insular echo chamber, fail to see the big picture, and end up making disastrous decisions.

By now, most of us think we have a good sense of the sorts of conditions that cause groups to fall into this trap. But how good is that understanding?

Let’s start with a thought experiment. If you had to guess, which of the following teams is the most likely to fall prey to the pathologies of groupthink?

A friendly team of long-term colleagues or a new collection of co-workers who haven’t had time to form close personal bonds?

A team composed of the usual suspects or that same team where an outsider has been brought in to provide a fresh perspective?

A group with a confident leader who has a clear vision of how to do things or a relatively unstructured group without a strong authority figure?

Intuitively, it might seem like the first group in each pair is the more likely to exhibit symptoms of groupthink, falling too quickly into overconfident consensus. But research actually suggests that it is often the second set of groups that is the more prone to this problem.

What most people fail to understand is how group behavior is driven by social identity (how people define themselves as a member of a group), which can push them either toward insularity and conformity or toward divergent thinking and dissent. What’s more, this isn’t just an academic curiosity. If people had a better sense of what conditions lead to groupthink, most groups in society would be able to function far more effectively.

Roots of groupthink

The term “groupthink” was coined in 1952, and psychologist Irving Janis popularized it a couple of decades later when he analyzed major missteps by powerful teams, including the Kennedy administration’s decision to invade Cuba at the Bay of Pigs and the Johnson administration’s decisions to escalate conflict in Vietnam. Mr. Janis described groupthink as, “a mode of thinking that people engage in when they are deeply involved in a cohesive in-group, when [their] striving for unanimity overrides their motivation to realistically appraise alternative courses of action.”

According to this logic, a longstanding team of collaborators would be especially vulnerable to groupthink. However, it turns out that findings supporting this conclusion were based largely on a specific situation that is actually quite rare in many organizations. Participants in experiments designed to test groupthink were generally meeting one another for the first time. Eager to establish friendly relations, people were unlikely to throw shade or disrupt a good beginning with expressions of sharp criticism.

But the picture turned out to be different among more genuinely close-knit groups. When researchers looked instead at behavior in groups composed of longer-term friends, they found that friendship was associated with less, not more, groupthink. The desire for cohesion, which is strong in new groups, isn’t necessarily the same thing as actual cohesion, especially in the form of personal bonds, which is often stronger in longer-term groups or teams.

There is an important lesson here: It is often the desire for cohesion that produces groupthink, not cohesion itself. And anything that threatens a group’s sense of cohesion may trigger people’s need to protect their identity and risks increasing groupthink.

Beware of outsiders

Misunderstanding what causes groupthink means that many of the perceived causes and solutions to fight it need to be rethought.

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For instance, one of the most popular antidotes for groupthink is to encourage groups to solicit external criticism—such as bringing in outsiders or consultants to provide alternative perspectives. Certainly this can provide groups with important new information, facts that could improve their decisions. But it guarantees nothing about how they will process the information they receive. Indeed, it can backfire as a solution to groupthink if it isn’t done properly.

Think about a tightly knit group you belong to. How do its members respond when a newcomer shows up? Do they welcome the outsider with open arms, eager to hear what they have to say? Or do they regard them with a degree of wariness, waiting to see how well they fit in with the group’s finely tuned culture?

Groups are often leery when outsiders enter their ranks and are all the more so when outsiders come to evaluate and criticize them. When management hires outside consultants to increase efficiency, for example, it might pose a threat to group cohesion. Will people be fired? Who is on the chopping block? When groups think they are likely to come under outside scrutiny, especially if they are worried about being held responsible for poor decisions, it can produce exactly the type of threat that leads to groupthink—a resistance rather than openness to divergent views.

The charismatic boss

Perhaps the biggest boogeyman when it comes to groupthink is a concern about charismatic leaders—an overpowering presence suppressing all divergence and dissent. Certainly, leaders can create environments where people are reluctant to voice their views. And there is no shortage of leaders who have created a cultlike allegiance in their organizations.

If anything, strong and effective leadership is crucial for preventing groupthink. It takes leadership to set the terms of the discussion, create fair and inclusive parameters for disagreement, ensure criticism is shared and establish healthy norms.

People are more willing to speak up when, at a minimum, they believe that they won’t be punished for offering divergent ideas. Ideally, dissent is valued and rewarded. Leaders have a responsibility to foster these feelings of “psychological safety.” Psychological safety is the reason friends feel more comfortable disagreeing than do new acquaintances. And it can be jeopardized by outsiders, however well intentioned their presence may be.

To help become the type of leader who can effectively guide a group without succumbing to groupthink, we offer some key lessons:

• Recognize that a lack of cohesion, when people are new to a team or don’t trust each other, is probably a greater contributor to groupthink than happy camaraderie. Building trust and a feeling of psychological safety is a key part of leadership.

• Be attentive to events that threaten the team’s identity and that might motivate people to turn inward and batten down the hatches. When appropriate, find ways to reduce these threats, removing outsider scrutiny or reducing the stakes of decisions, so that your team can focus on the job at hand rather than worry about how they are being judged.

• Tackle these threats directly and reward the right behavior. Understand that you need to enrich a cohesive group with healthy social norms, procedures and incentives that will mitigate groupthink and foster constructive dissent. Help your team see scrutiny as a source of strength, not weakness, and reward people for seeking out constructive criticism. Or to paraphrase Gen. George Patton, embrace the notion that if everyone is thinking alike, then someone isn’t thinking.

• Make sure your team is working toward the right goals. Sometimes managing public relations is the priority, but is that what you want them to be doing this time? It’s critical to signal when it’s appropriate to think about the external, political considerations and when it isn’t.

Understanding how groups operate isn’t easy. But wrapping our head around the science of identity is fundamental to getting smarter about groups and building smarter groups.

Dr. Van Bavel, an associate professor of psychology and neural science at New York University, and Dr. Packer, a professor of psychology at Lehigh University, are the authors of “The Power of Us: Harnessing Our Shared Identities to Improve Performance, Increase Cooperation, and Promote Social Harmony.” They can be reached atreports@wsj.com.