Summary: Aggression towards members of an “outgroup” was associated with increased activity in areas of the brain associated with reward. Activity in the ventromedial prefrontal cortex impacted a person’s level of aggression toward a stranger.
Source: Virginia Commonwealth University
Humans tend to form groups, which often find themselves in conflict with rival groups. But why do people show such a tendency to harm members of opposing groups?
A new study by researchers at Virginia Commonwealth University has used functional brain imaging technology to reveal a potential answer: it increases activity in the brain’s reward network.
“At a time of deepening political divisions and global conflict, it is crucial for us to understand why people split into ‘us’ and ‘them’ and then show a deep will to ‘harm them’,” said corresponding author David. Chester, Ph.D., associate professor in the Department of Psychology at the College of Humanities.
“Our results advance this understanding by suggesting that harming outgroup members is a relatively rewarding experience.”
The researchers asked 35 male students to perform a competitive and aggressive task against a student from their university or what they were told was a rival university. In reality, the contestants were unknowingly playing against a computer program and no real people were harmed.
They found that participants who were more aggressive toward outgroup members (students from a rival university) compared to ingroup members (students from their own university) exhibited greater activity in central regions of the the brain’s reward circuitry – the nucleus accumbens and the ventromedial prefrontal cortex – as they decided how aggressive to be.
Before and after outgroup exclusion, aggression toward outgroup members was positively associated with activity in the ventral striatum when making decisions about the degree of aggression toward the outgroup adversary.
Aggression towards outgroup members was also linked to greater post-exclusion activity in the rostral and dorsal medial prefrontal cortex when provoking their outgroup opponent. These altered patterns of brain activity suggest that frontostriatal mechanisms may play an important role in motivating aggression toward outgroup members.
The results suggest that harming outgroup members is particularly rewarding and associated with experiencing positive emotions. Such psychological reinforcement mechanisms may help explain why humans seem so prone to intergroup conflict, Chester said.
“This finding helps balance the narrative of psychological processes that underlie aggression against outgroup members, which typically emphasizes negative emotional states such as anger and fear,” Chester said.
“This study showed that positive emotions may play a role in motivating intergroup aggression, suggesting many new directions for future research on this topic and illuminating potential interventions to reduce group conflict.”
The findings raise the possibility that one day, treatments that disrupt the reward of intergroup aggression could help reduce the costly and persistent human phenomenon of violence toward other groups, Chester said.
Chester is director of VCU’s Social Psychology and Neuroscience Lab, which seeks to understand why people try to harm themselves. In the past, the lab has focused on conflicts between two individuals and sought to remove any elements of group affiliation, identity, or partisanship in carefully controlled experiments.
This new study, however, is the lab’s first foray into exploring the neural correlates of intergroup aggression.
“These new findings align well with our previous research, which has repeatedly implicated the brain’s reward circuits (i.e., nucleus accumbens and ventromedial prefrontal cortex) in promoting aggressive acts,” said he declared.
“We have advanced this line of investigation by showing that such reward activity during aggression exerts even more of an effect in an intergroup context than in a non-group context.”
Although the researchers were not surprised by the new findings, they were surprised to find such results even when experimenting with weak group rivalry.
“Many groups have ancient histories of deep hatred for each other, and our use of rival universities hasn’t even captured what many really problematic intergroup conflicts look like around the world,” Chester said.
“We chose such a lighthearted intergroup rivalry for several reasons, one of the main ones being that invoking deep-rooted intergroup conflict could cause our participants undue distress. But it was still surprising to see such clear results despite our use of a relatively minor intergroup rivalry.
“I suspect our observed effect would be even stronger in the context of an intergroup conflict between two groups that deeply dislike each other.”
The area of the brain involved in learning is not only associated with reward, it is also involved in other psychological processes such as learning, motivation and identity.
While Chester said it’s possible brain activity doesn’t reflect the subjective experience of pleasure, decades of brain research suggest that the area’s core functions are reliably linked to point reward. where the researchers felt comfortable making the inference, Chester said.
Further research would be needed to say with certainty that reward is the “underlying culprit of intergroup conflict”, he said.
About this social neuroscience research news
Author: Press office
Source: Virginia Commonwealth University
Contact: Press Office – Virginia Commonwealth University
Image: Image is in public domain
Original research: Free access.
“Neural Mechanisms of Intergroup Exclusion and Retaliatory Aggression” by Emily Lasko et al. Social neuroscience
Neural mechanisms of intergroup exclusion and retaliatory aggression
Aggression occurs frequently and severely between rival groups. Although there have been many studies on the psychological and socio-ecological determinants of intergroup aggression, the neuroscience of this phenomenon remains incomplete.
To examine the neural correlates of aggression directed at outgroup (versus ingroup) targets, we recruited 35 healthy young male participants who were current or former students of the same university.
While undergoing a functional MRI, participants performed an aggression task against an ingroup and outgroup adversary in which their adversaries repeatedly provoked them to different levels, and then the participants could retaliate.
Participants were then socially included and then excluded by two outgroup members, and then performed the same aggression task against the same two opponents. Before and after outgroup exclusion, aggression toward outgroup members was positively associated with activity in the ventral striatum when making decisions about the degree of aggression toward the outgroup adversary.
Aggression towards outgroup members was also linked to greater post-exclusion activity in the rostral and dorsal medial prefrontal cortex when provoking their outgroup opponent.
These altered patterns of brain activity suggest that frontostriatal mechanisms may play an important role in motivating aggression towards outgroup members.