Mobs can make even the most reasonable individual capable of committing heinous crimes. A new study by the Massachusetts Institute of Technology tries to understand why good people in a crowd do bad things.

Reasons that drive this group mentality, researchers say, include the sense of anonymity and the idea that chances of being punished for a violent act are low. Also, individuals in a crowd tend to ignore personal responsibility for their actions.

A related study had earlier found that it takes just five percent of the crowd to influence the herd mentality; the other 95 percent just follow.

In the current study, researchers conducted several experiments to determine what goes on in the brains of people who are most influenced by the crowd mentality. Turns out that people who can't differentiate between 'self' and 'group' are most likely to go with the flow. These people, according to researchers, tend to lose a sense of personal moral beliefs.

 "A group of people will often engage in actions that are contrary to the private moral standards of each individual in that group, sweeping otherwise decent individuals into 'mobs' that commit looting, vandalism, even physical brutality," said Rebecca Saxe, an associate professor of cognitive neuroscience at MIT, according to a news release.

For the study, researchers looked at a part of the brain called medial prefrontal cortex, which is associated with reflection about self. When an individual is thinking about self, the medial prefrontal cortex shows an increase in activity. Researchers used functional magnetic resonance imaging (fMRI) brain scans to assess participants' behavior.

In the study, volunteers completed several tasks, individually and in groups.

Researchers found that when playing individually, participants had more activity in medial prefrontal cortex when they saw statements about themselves.

However, in some people this difference in brain activity was lesser, meaning that they couldn't differentiate between self and group. These people were especially more likely to harm members of a rival group.

According to Mina Cikara, a former MIT postdoc and lead author of the study, in some cases reflecting on one's own moral standards can help people avoid the mob mentality.

"This is a nice way of using neuroimaging to try to get insight into something that behaviorally has been really hard to explore," said David Rand, an assistant professor of psychology at Yale University, who was not involved in the research. "It's been hard to get a direct handle on the extent to which people within a group are tapping into their own understanding of things versus the group's understanding."

The study is published in the journal NeuroImage. It was funded by Eunice Kennedy Shriver National Institute of Child Health and Human Development and others.