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Zachary’s Karate Club Network

Anyone getting familiar with SNA will stumble upon Zachary’s karate club network sooner or later. Yes, it’s an actual karate club; no, it isn’t some exclusive SNA stress relief program and it isn’t, in fact, Zachary’s club. Zachary’s the guy who collected data on how the different members of a small university-based karate club interacted outside the club, so basically: did those dudes (dudettes?!) hang out during non-karate-related stuff?

The Karate Club Network: visualisation of friendships

karate club network karate.jpg

The Karate Club Network: two groups

He whipped up a nice network and as you can no doubt also see on the graph, he discerned two groups. One is centered around the instructor (#1 on the left), and one around the club president (#34 to the right). And, as in every group, there are some in the middle who just can’t decide. Or don’t want to, out of principle. Posers. But what’s interesting is that these factions were never recognized by the members themselves.
As an experiment then, Zachary used Ford & Fulkerson’s maximum flow – minimum cut labeling procedure to determine to which group these crowd-pleasers actually leaned to. All hypothetically of course.

The Karate Club Network: hypothesis turned reality

Be careful what you wish for, they say. Well, in Zachary’s case, he may not have actually hoped for it, but it certainly didn’t harm his case: after a collision between the president and the instructor, the club split in, could you ever have guessed, two. The factions Zachary predicted in his model appeared to be, in fact, very real. Only one guy (#9) who was attributed to the president’s group in the model actually joined the instructor’s club after the fission (yup, he was one of those posers). On the total of 34 members involved in the experiment, that’s a 97% success rate for Zachary’s model.

Karate Club Network: Bibliography

Ford, L. & Fulkerson, D. (1962), Flow in Networks, Princeton.

Zachary, W. W. (1977), ‘An Information Flow Model for Conflict and Fission in Small Groups’, Journal of Anthropological Research 33, 452-473.

Why am I telling you all this, you ask? Well, I have recently discovered that there is a Zachary Karate Club Club. And you can win trophies. All you have to do is be the first to use Zachary’s karate club as an example at any conference on networks. You get a TROPHY people.
So it’s that easy, huh? I’ve always wanted to become a member of the Order of the Garter. I might just whip up a network of these chivalrous knights this weekend; I’ve got plenty of networky conferences coming up….


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