Brain Synchronization During Inter-Group Hostility
Post by D. Chloe Chung
What's the science?
When we belong to a certain group of people who share similar thoughts or goals with us, we feel safe and work together to accomplish things as a group that we could have not achieved on our own. Despite this benefit, such group mentality and behavior can also lead to negative situations as it can reduce our sense of individuality, prompting us to act in a riskier way, and amplifying hostility towards opponent groups. Previous studies have shown that neural activity of specific brain areas can be synchronized across people who experience collective thinking and group behavior, but this idea has not been tested in the context of group-level hostility. This week in Nature Neuroscience, Yang and colleagues used a non-invasive imaging technique to investigate the neural mechanism underlying inter-group hostility.
How did they do it?
The authors recruited 546 male participants at the age of 18 to 30 and randomly divided them into 182 three-person groups. Two groups were matched to have 24 rounds of competition, where one group was assigned to be the “attacker group” that can aggress the opposite “defender group”. Each participant was given a hypothetical budget from which one could contribute a portion to the team’s ability to defeat the opponent team (“fighting capacity”). If the attacker group had a larger sum of fighting capacity, they could claim the remaining budget of the defender group. However, if the defender group had a larger or equal sum of fighting capacity, both groups could keep their remaining budget. Importantly, if the groups were selected to engage in the in-group bonding exercise, participants wore the same-color team vest (black or white, based on what each person chose during the survey prior to competition) and discussed shared preferences within the group. On the contrary, if the groups were selected to be in the no-bonding control group, they did not wear team vests and discussed neutral topics. During the competition, participants underwent functional near-infrared spectroscopy (fNIRS) to measure individual brain activity in two regions that are important for decision-making: the right dorsolateral prefrontal cortex (rDLPFC) and right temporoparietal junction (rTPJ).
What did they find?
The authors found that defender groups made more contributions towards their fighting capacity than attacker groups. Also, participants who underwent the in-group bonding exercise sacrificed more for the group by making larger contributions and displayed more coordinated behaviors with the same group members. The authors observed that in-group bonding decreased neural activity in the DLPFC, the brain region known to be involved in the inhibition of impulses. Conversely, in-group bonding increased functional connectivity between the rDLPFC and the rTPJ, a brain region that becomes activated during cooperation. These data suggest that an in-bonding exercise can modulate neural activity, resulting in disinhibition and higher risk-taking for the group’s collective goal. Interestingly, the authors found that neural activities in both the rDLPFC and the rTPJ were more synchronized in the in-group bonding condition, specifically in the attacker group. When rDLPFC activity was more synchronized within the group, it was also more likely that the attackers would make a larger contribution to fighting capacity, indicating that neural synchronization has a meaningful link to how people express hostility in a group.
What’s the impact?
The authors utilized functional neuroimaging to reveal the neural mechanisms that underlie inter-group conflicts, providing further evidence for neural synchronization as an important mechanism in inter-group hostility. Their findings suggest that group-level hostility, which can be enhanced by in-group bonding, may be mediated by collectively decreased risk aversion among group members. During this modern era where conflicts between groups with various values and ideologies are not uncommon, this study sheds important light on what happens in our brains when we become hostile towards others.
Yang et al. Within-group synchronization in the prefrontal cortex associates with intergroup conflict (2020). Access the original scientific publication here.