"""
We were interested in whether we could induce the monkey society we were studying to change from its status quo of many small fights and a few large ones to having many large fights. We observed that fights in this monkey group range in size from two to 30 or so individuals, with small fights common and large fights very rare. By simulating the society using data we had collected on fight-joining decisions, we found that we could measure the number of monkeys whose propensity to join fights would have to increase to move the system closer to the critical point.
That sounds like they were just simulating the society based on data they had gathered about their fights. So not inducing monkey fights, just observing the monkeys fighting naturally and extrapolating from there. Though earlier in the article they allude to removing a few members of the society and showing the fights increased.
Also it should be noted that fighting is a very common part of monkey behavior. If you observe these groups in the wild individuals are almost constantly challenging and checking others to maintain or advance their position in the social hierarchy.
""" We were interested in whether we could induce the monkey society we were studying to change from its status quo of many small fights and a few large ones to having many large fights. We observed that fights in this monkey group range in size from two to 30 or so individuals, with small fights common and large fights very rare. By simulating the society using data we had collected on fight-joining decisions, we found that we could measure the number of monkeys whose propensity to join fights would have to increase to move the system closer to the critical point.