[LINK] "How Facebook ‘Contagion’ Spreads"

[rfmcdonald]

Sarah C.P. Williams' summary of recent research on the mechanics of social networks, hosted at Wired Science, is thought provoking.

Previous research on how people make decisions — whether to buy a product, attend a show, or pick up a new hobby — has concluded that the more people you know who do something, the more likely you are to do it. But that’s not what computer scientist Jon Kleinberg of Cornell University and colleagues found when they started analyzing data on decisions to join social media networks.

The team collected data from 54 million Facebook invitation e-mails. When people sign up to use Facebook, they are given the opportunity to send invitations to anyone in their e-mail address book who is not already a member of the site. The invitation includes the name of the member who initiated the e-mail as well as any the names of Facebook user who has previously imported the recipient’s e-mail address. So with each invitation someone gets, their list of potential friends on subsequent messages grows. The data the researchers — who included a collaborator within Facebook — analyzed included the friends listed, those friends’ demographics and connections within the Facebook network, and whether the invitee joined the site. The team also used data on how frequently new Facebook members ended up using the site over the next 3 months.

“What jumped out at us was that someone’s likelihood of joining really corresponded not to the number of friends represented, but to how many disconnected groups the friends listed on the e-mail fell into,” Kleinberg says. “We were surprised by how clean the effect was.”

If four people who were all connected via Facebook friendships were listed on the invitation, for example, the recipient was as likely to join the site as if one friend was listed. But if the message contained the names of four people who had no direct Facebook friendships between them, the odds of the recipient joining the site more than doubled. Moreover, new Facebook members whose first 20 friends fell into multiple distinct groups were much more likely to stay engaged with the site — visiting Facebook 6 of 7 days a week 3 months after registering — than those who had 20 friends all within one connected group, Kleinberg’s team reports online today in the Proceedings of the National Academy of Sciences.

Williams quotes a third party as speculating that perhaps having many different people on an invite list increases the likelihood of having a member of a social group particularly important to a person sign up, or perhaps the representation of people from multiple discrete circles is key. Speaking of my own experience, I know that the fact that most of my active friends on Google+ come from a single group does make me rate that service as less noteworthy than a Facebook where almost everyone is represented.

The paper, "Structural diversity in social contagion", is available in full here.