September 15, 2011

A healthy society keeps aggressive individuals in check, just as a healthy immune system controls infection. At both the cellular and societal levels, conflict can spread through contagion, and new research by SFI scientists reveals an efficient means of containing it.

SFI Professors David Krakauer and Jessica Flack and their colleague Karen Page (University College London) investigated two strategies for mitigating social aggression that Flack had observed in a society of pigtailed macaque monkeys.

In one strategy, monkeys tried to pacify aggressors, approaching them before a fight or during a break in fighting to try to persuade them to become passive. By contrast, some monkeys directly and aggressively intervened during fights to subdue brawlers. The latter approach, which biologists call policing, was displayed primarily by a small subset of monkeys who were socially powerful.

To investigate the relative merits of policing versus pacifying aggression, the scientists used mathematical models inspired by the dynamics of immune system T and B cells. The models showed that policing, which is similar, roughly speaking, to T cells directly attacking contagions, was the far more efficient strategy for containing aggression. This held so long as the police were socially powerful, as was observed in the macaque society.

“The data indicate that a small subset of the group performs policing, everyone engages in pacifying, and policing is better than pacifying at controlling the escalation of aggression when the policers are powerful,” the researchers wrote in a paper published recently in PLoS One.

They also warned against an overly-powerful police force, likening it to an auto-immune disorder in which an over-active immune system attacks healthy cells.

In future work, the researchers intend to explore other parallels between immune system dynamics and social conflict.

Read the PLoS One paper (August 24, 2011)