Rousing public speeches are meant to stir powerful emotions in those who listen. A new psychological study found that these emotions could predict when groups have been incited to commit acts of violence or terrorism.

David Matsumoto, a professor of psychology at San Francisco State University, analyzed speeches delivered by government, activist and terrorist leaders and concluded that leaders’ expressions of anger, contempt and disgust spiked immediately before their group committed an act of violence. His study was   published in the August issue of the journal Behavioral Sciences of Terrorism and Political Aggression.

Matsumoto told Homeland1 the study is important for several reasons. "For one, it contributes to basic science knowledge about the role of emotions in aggression and intergroup relations."

He said that in particular the findings concerning the importance of contempt and disgust, along with anger, are novel and unique in the field and open the door to much more research and theorizing in the future.

The findings may also have practical applications. Matsumoto said many politically or ideologically motivated groups, whether they’re pro- or anti-abortion rights, gun ownership or the death penalty or they represent a religious viewpoint, have groups that oppose them and their ideology.

Yet some groups become violent while others do not. What drives some to violence? One factor to be considered is emotion. Thus, understanding the roots of decisions and behaviors requires an understanding of the emotions underlying them.

"Monitoring the expression of emotions by group leaders may provide not only early warning mechanisms of impending possible aggression, but also a method to gauge the effects of one’s own group’s actions on other groups," Matsumoto said.

He said developing systems to assess emotions among members of groups, and at different levels within the groups, might provide a way to gain insights about the degree to which emotion-sharing may occur within groups, which may be important for political justification of leaders' decisions.

"Such systems may be akin to rumor-monitoring systems that are useful in assessing counter-insurgency operations in many areas of the world, where the battle concerning knowledge and information is as important as kinetic operations," he said.