Sunstein explains the inner workings of the rumor mill


Professor Cass Sunstein ’78

Why do some people believe that President-elect Barack Obama ’91 is a Muslim? How is it that such a completely false claim could be universally accepted in some communities? As children we were told that it is rude to gossip about others, but according to Professor Cass Sunstein ’78, there are innate social forces that can strongly impact the vulnerability of individuals to persuasion and the propagation of false information.

Sunstein believes that the spread of rumors is facilitated by phenomena he calls propagators, informational cascades, and group polarization, with the result that a large number of people may steadfastly believe something which is patently untrue.

The spread of false rumors by these means can quickly cause permanent damage to individuals and organizations, and this has serious implications for the nature of democracy in the digital age of instant communication. He explored the nature of these phenomena and their implications on free speech in a lecture entitled, “He said THAT? She said WHAT? On False Rumors and Free Speech”, which he delivered on the occasion of his recognition as Felix Frankfurter Professor of Law on Wednesday, December 3.

Aspects of individual psychology create an internal predisposition toward or against the acceptance of rumors that are of uncertain validity. For example, when it was announced by multiple news networks that it had been demonstrated that no weapons of mass destruction existed in Iraq, people who already doubted their presence were affirmed in their belief, but strangely, so were people who believed they existed. Individuals may resist accepting a refutation of a false belief because of the unpleasant cognitive dissonance created by the idea of being wrong. In contrast, if an individual is predisposed toward a particular opinion, such as the belief that the death penalty has strong deterrent effect, then information which supports that position will be accepted even when of dubious validity.

The spread of information is profoundly affected by hidden psychological and social mechanisms, says Sunstein. Propagators are individuals who spread a piece of false information to others, and the reputation of the propagator can significantly affect the acceptance of a rumor, causing another to ignore their own disbelief. This can then lead to the rumor spreading on to the next person and outward from the propagator in a cascade due to each person’s reputation with the next. According to Sunstein, this dynamic can result in multiple, unstable equilibria, because depending on the way in which the information is communicated it may continue to spread or be disbelieved.

Two factors which lead to continued cascading of information are the awareness of individuals that others believe a rumor and group polarization. In some cases, the simple fact that many people have already accepted a particular rumor will be sufficient to overwhelm their internal signals which would lead them to normally disbelieve it. This means that once a rumor gets accepted by a certain number of individuals it may spread rapidly.

Furthermore, when an entire group is exposed to a rumor at once and are able to discuss it together, many individuals who are only slightly inclined toward believing the claim can reinforce each others’ beliefs through agreement. The group may then develop a homogeneous acceptance or rejection of the rumor which is more extreme than the view any isolated individual would have held.

The pernicious effects of group psychology are magnified by the large and dynamic social networks formed on the Internet and ossified by the permanent nature of public postings. The result is that a rumor, no matter how unfounded, can spread quickly and cause permanent damage, and this could be potentially devastating for public figures, organizations, and businesses for whom reputation is essential. Therefore, it may be necessary for free speech to be chilled in the area of rumors and false speech, since without an impairment to the natural social propagation of such rumors, permanent damage might be caused by an unfounded statement.

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