Contagion in natural and social systems

An interesting article on contagion in social networks was recently published in Science 329, 1194–1197 (2010). Here is how Nature summarized the findings:

A person needs contact with only one infected individual to catch a disease. But new behaviours can be harder to catch, with people often needing to have contact with several others who have adopted a behaviour before deciding to do so themselves. Damon Centola at the Massachusetts Institute of Technology in Cambridge set up an online community, instigated a behaviour — registering for an online health forum — and watched as it spread through the network.

He found that more people who were in ‘clustered’ communities (pictured right) joined the forum than people in communities with ‘random’ networks (left). This, Centola says, was because people in clusters tended to receive encouragement from several members of their social network.