Chain Letters Flow Deep and Narrow

A study published by the (US) National Academy of Sciences demonstrates that email, at least, follows a meandering path to large audiences, rather than a short path via online influencers. Tracing information flow on a global scale using Internet chain-letter data, by David Liben-Nowell and Jon Kleinberg (via IntelFusion). The choice of email as the channel guarantees the deep and narrow result.

Although information, news, and opinions continuously circulate in the worldwide social network, the actual mechanics of how any single piece of information spreads on a global scale have been a mystery. Here, we trace such information-spreading processes at a person-by-person level using methods to reconstruct the propagation of massively circulated Internet chain letters. We find that rather than fanning out widely, reaching many people in very few steps according to "small-world" principles, the progress of these chain letters proceeds in a narrow but very deep tree-like pattern, continuing for several hundred steps. This suggests a new and more complex picture for the spread of information through a social network. We describe a probabilistic model based on network clustering and asynchronous response times that produces trees with this characteristic structure on social-network data.
For anyone who's received chain email from family and friends, this shouldn't come as a surprise. Many of those who forward chain letters don't know to prune email headers, so the path taken by incoming chain letters is frequently plain to see. Somebody's friend's cousin's neighbor's daughter received this and thought a few close people really should know about it, and before you know it, I get a copy in my inbox.

Deep and Wide
The more interesting question—and the more challenging—is to track the spread of information and opinions across the many channels people use, both online and offline. If you think about the interaction between mass media and offline word of mouth, it's clear that dissemination can alternate between wide (mass media) and narrow (interpersonal). Online media work the same way, with some sources reaching large audiences while other channels move information among friends.

The transition from wide to narrow can happen at any time in the process and can go in either direction:

  • Narrow –> Wide
    Email to blogger, low readership blog to A-list blog, blog post picked up by mass media, interpersonal to media (conversation with a reporter)

  • Wide –> Narrow
    Mass media to blogs, online media to email, media to interpersonal
Picture water flowing downhill. If there's a wide channel available, water will use it. If there's a narrow channel, it will use that. Where both are available, it uses both. Information works the same way. The key is that water wants to flow downhill. To make this work with ideas, you need ideas that people want to communicate.

Suddenly, I want to go play in the creek. I'll call it work-related.


About Nathan Gilliatt

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  • Voracious learner and explorer. Analyst tracking technologies and markets in intelligence, analytics and social media. Advisor to buyers, sellers and investors. Writing my next book.
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