orgtheory.net

Over at Scatter, Andrew asked about a classic issue in network theory. Is influence really asserted through the tie, or is it really just correlated personal characteristics? Does Brayden influence me because we know each other, or because we tend to think the same things because we are both cool dudes?*

Brendan Nyhan sent me a link a few weeks ago addressing this issue. Here’s the summary of a working paper by Cosma Shalizi and Andrew C. Thomas:

1. Influence or social contagion: Because they are friends, Joey’s example inspires Irene to jump. Or, more subtly: seeing Joey jump re-calibrate’s Irene’s tolerance for risky behavior, which makes jumping seem like a better idea.
2. Biological contagion: Joey is infected with a parasite which suppresses the fear of heights and/or falling, and, because they are friends, Joey passes it on to Irene.
3. Manifest homophily: Joey and Irene are friends because they both like to jump off bridges (hopefully with bungee cords attached).
4. Latent homophily: Joey and Irene are friends because they are both hopeless adrenaline junkies, and met through a roller-coaster club; their common addiction leads both of them to take up bridge-jumping.
5. External causation: Sometimes, jumping off a bridge is the only sane thing to do:

Check it out.

* It’s just an example, Brayden. Calm down