Social media has caught a lot of flack, lately, for getting people to collectively make dumb decisions. It’s an example of the psychological theory of groupthink: the more people talk to each other, the more they’re likely to talk themselves into irrationality in order to reach consensus.

Except, a new study has upended this theory, finding the opposite can be true: Groupthink can make people smarter.

“We find that even if people are not particularly accurate, when they talk to each other, they help to make each other smarter,” said Damon Centola, an associate professor at the University of Pennsylvania’s Annenberg School for Communication and School of Engineering and Applied Science and director of the Network Dynamics Group. “Whether things get better or worse depends on the networks.

“In egalitarian networks,” he said, “where everyone has equal influence, we find a strong social-learning effect, which improves the quality of everyone’s judgments. When people exchange ideas, everyone gets smarter. But this can all go haywire if there are opinion leaders in the group.”

An influential opinion leader can hijack the process, leading the entire group astray. While opinion leaders may be knowledgeable on some topics, Centola found that, when the conversation moved away from their expertise, they still remained just as influential. As a result, they ruined the group’s judgment, upholding the traditional view of grouthink mentality.

“On average,” he said, “opinion leaders were more likely to lead the group astray than to improve it.”

The online study included more than 1,300 participants, who were placed into one of three experimental conditions. Some were placed into one of the “egalitarian” networks, in which everyone had an equal number of contacts and everyone had equal influence. Others were placed into one of the “centralized” networks, in which a single opinion leader was connected to everyone, giving that person much more influence in the group. Each of the networks contained 40 participants. Finally, Centola had several hundred subjects participate in a “control” group, without any social networks.

In the study on the effects of groupthink, all of the participants were given a series of estimation challenges, such as guessing the number of calories in a plate of food. They were given three tries to get the right answer. Everyone first gave a gut response.

Then, participants who were in social networks could see the guesses made by their social contacts and could use that information to revise an answer. They could then see their contacts’ revisions and revise their answers again. But this time it was their final answer. Participants were awarded as much as $10 based on the accuracy of their final guess. In the control group, participants did the same thing, but they were not given any social information between each revision.

“Everyone’s goal was to make a good guess. They weren’t paid for showing up,” Centola said, “only for being accurate.”

Patterned effects of groupthink began to emerge. The control groups initially showed the classic “wisdom of the crowd” — the idea that the majority of any large-enough group will turn up the right answer — but did not improve as people revised their answers. Indeed, if anything, they got slightly worse. By contrast, the egalitarian networks also showed the classic wisdom of the crowd — but then saw a dramatic increase in accuracy. Across the board, in network after network, the final answers in these groups were consistently far more accurate than the initial wisdom of the crowd.

“In a situation where everyone is equally influential,” Centola said, “people can help to correct each other’s mistakes. This makes each person a little more accurate than they were initially. Overall, this creates a striking improvement in the intelligence of the group. The result is even better than the traditional wisdom of the crowd! But, as soon as you have opinion leaders, social influence becomes really dangerous.”

In the centralized networks, Centola found that, when the opinion leaders were very accurate, they could improve the performance of the group. But even the most accurate opinion leaders were consistently wrong some of the time.

“Thus,” Centola said, “while opinion leaders can sometimes improve things, they were statistically more likely to make the group worse off than to help it.

These findings on the pros (and cons) of groupthink have wide-ranging real-world implications — in areas as critical and universal as climate-change science and medical decision-making, and as mundane as your teen’s idiot friend-clique and your weekly departmental meetings.

“It’s much better to have people talk to each other and argue for their points of view than to have opinion leaders rule the crowd,” he said. “By designing informational systems where everyone’s voices can be heard, we can improve the judgment of the entire group. It’s as important for science as it is for democracy.”

Ph.D. candidate Joshua Becker and recent Ph.D. graduate Devon Brackbill helped author the study, published in the Proceedings of the National Academy of Sciences.