What Is the Optimal Size of A Network?

According to the latest research of the US Army, the well-known Dunbar number theory holds true, that is, a network with no more than 150 members works best for effective information exchange.

“This marks the beginning of a new approach to deal with competition and conflict in today's complex world,” said Dr. Bruce West, a senior scientist at the Army Research Office. “To improve the utility of the army's network structure in terms of robustness, resilience, adaptability, and efficiency requires a deeper understanding of how our networks, and those of our adversaries, actually work.”

Researchers from the ARO and the University of North Texas tested a theory developed by British anthropologist Robin Dunbar in the 1990s that 150 is the largest group in which humans can maintain stable social relationships. Around that size, social groups become unstable and split into smaller groups.

Retired army general Stanley McChrystal wrote in his book Team of Teams: New Rules of Engagement for a Complex World: “In order to defeat a network can, we have become a network ourselves.” He discussed his understanding of Dunbar numbers with lessons learned from Iraq's battlefield and answered how to fight a loosely networked but effective AI Qaeda.

The researchers published their findings in the Proceedings of the National Academy of Sciences, suggesting that networks of certain sizes have better information transmission than others, and networks with no more than 150 nodes are the best choice.

West, the co-author of the paper, said: “The basic characteristic of network is the relationship between its function and size, which is why the Dunbar number theory is very important.”

The researchers propose that 150 is the result of internal dynamics of self-organized complex networks within social systems.